Any for CertParamType type

request context tracks session access

.azure-pipelines.yml

@@ -1,84 +0,0 @@
-trigger:
-  - 'master'
-  - '*.x'
-
-jobs:
-  - job: Flask
-    variables:
-      vmImage: ubuntu-latest
-      python.version: '3.7'
-      python.architecture: 'x64'
-      TOXENV: 'py,coverage-ci'
-      publish.test.results: 'true'
-
-    strategy:
-      matrix:
-        Python37Linux:
-          python.version: '3.7'
-        Python37Windows:
-          python.version: '3.7'
-          vmImage: 'windows-latest'
-        Python37Mac:
-          python.version: '3.7'
-          vmImage: 'macos-latest'
-        Pypy3Linux:
-          python.version: 'pypy3'
-        Python36Linux:
-          python.version: '3.6'
-        Python35Linux:
-          python.version: '3.5'
-        Python27Linux:
-          python.version: '2.7'
-        Python27Windows:
-          python.version: '2.7'
-          vmImage: 'windows-latest'
-        DocsHtml:
-          TOXENV: 'docs-html'
-          publish.test.results: 'false'
-        VersionRange:
-          TOXENV: 'devel,lowest,coverage-ci'
-
-    pool:
-      vmImage: $[ variables.vmImage ]
-
-    steps:
-      - task: UsePythonVersion@0
-        inputs:
-          versionSpec: $(python.version)
-          architecture: $(python.architecture)
-        displayName: Use Python $(python.version)
-
-      - script: pip --disable-pip-version-check install -U tox
-        displayName: Install tox
-
-      - script: tox -- --junitxml=test-results.xml tests examples
-        displayName: Run tox
-
-      - task: PublishTestResults@2
-        inputs:
-          testResultsFiles: test-results.xml
-          testRunTitle: $(Agent.JobName)
-        condition: eq(variables['publish.test.results'], 'true')
-        displayName: Publish test results
-
-      - task: PublishCodeCoverageResults@1
-        inputs:
-          codeCoverageTool: Cobertura
-          summaryFileLocation: coverage.xml
-        condition: eq(variables['publish.test.results'], 'true')
-        displayName: Publish coverage results
-
-  # Test on the nightly version of Python.
-  # Use a container since Azure Pipelines may not have the latest build.
-  - job: FlaskOnNightly
-    pool:
-      vmImage: ubuntu-latest
-    container: python:rc-stretch
-    steps:
-      - script: |
-          echo "##vso[task.prependPath]$HOME/.local/bin"
-          pip --disable-pip-version-check install --user -U tox
-        displayName: Install tox
-
-      - script: tox -e nightly
-        displayName: Run tox

.devcontainer/devcontainer.json

@@ -0,0 +1,17 @@
+{
+  "name": "pallets/flask",
+  "image": "mcr.microsoft.com/devcontainers/python:3",
+  "customizations": {
+    "vscode": {
+      "settings": {
+        "python.defaultInterpreterPath": "${workspaceFolder}/.venv",
+        "python.terminal.activateEnvInCurrentTerminal": true,
+        "python.terminal.launchArgs": [
+          "-X",
+          "dev"
+        ]
+      }
+    }
+  },
+  "onCreateCommand": ".devcontainer/on-create-command.sh"
+}

.devcontainer/on-create-command.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+set -e
+python3 -m venv --upgrade-deps .venv
+. .venv/bin/activate
+pip install -r requirements/dev.txt
+pip install -e .
+pre-commit install --install-hooks

.editorconfig

@@ -0,0 +1,13 @@
+root = true
+
+[*]
+indent_style = space
+indent_size = 4
+insert_final_newline = true
+trim_trailing_whitespace = true
+end_of_line = lf
+charset = utf-8
+max_line_length = 88
+
+[*.{css,html,js,json,jsx,scss,ts,tsx,yaml,yml}]
+indent_size = 2

.gitattributes

@@ -1 +0,0 @@
-CHANGES.rst merge=union

.github/ISSUE_TEMPLATE.md

@@ -1,33 +0,0 @@
-**This issue tracker is a tool to address bugs in Flask itself.
-Please use the #pocoo IRC channel on freenode or Stack Overflow for general
-questions about using Flask or issues not related to Flask.**
-
-If you'd like to report a bug in Flask, fill out the template below. Provide
-any any extra information that may be useful / related to your problem.
-Ideally, create an [MCVE](http://stackoverflow.com/help/mcve), which helps us
-understand the problem and helps check that it is not caused by something in
-your code.
-
----
-
-### Expected Behavior
-
-Tell us what should happen.
-
-```python
-Paste a minimal example that causes the problem.
-```
-
-### Actual Behavior
-
-Tell us what happens instead.
-
-```pytb
-Paste the full traceback if there was an exception.
-```
-
-### Environment
-
-* Python version:
-* Flask version:
-* Werkzeug version:

.github/ISSUE_TEMPLATE/bug-report.md

@@ -0,0 +1,27 @@
+---
+name: Bug report
+about: Report a bug in Flask (not other projects which depend on Flask)
+---
+
+<!--
+This issue tracker is a tool to address bugs in Flask itself. Please use
+GitHub Discussions or the Pallets Discord for questions about your own code.
+
+Replace this comment with a clear outline of what the bug is.
+-->
+
+<!--
+Describe how to replicate the bug.
+
+Include a minimal reproducible example that demonstrates the bug.
+Include the full traceback if there was an exception.
+-->
+
+<!--
+Describe the expected behavior that should have happened but didn't.
+-->
+
+Environment:
+
+- Python version:
+- Flask version:

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,11 @@
+blank_issues_enabled: false
+contact_links:
+  - name: Security issue
+    url: https://github.com/pallets/flask/security/advisories/new
+    about: Do not report security issues publicly. Create a private advisory.
+  - name: Questions on GitHub Discussions
+    url: https://github.com/pallets/flask/discussions/
+    about: Ask questions about your own code on the Discussions tab.
+  - name: Questions on Discord
+    url: https://discord.gg/pallets
+    about: Ask questions about your own code on our Discord chat.

.github/ISSUE_TEMPLATE/feature-request.md

@@ -0,0 +1,15 @@
+---
+name: Feature request
+about: Suggest a new feature for Flask
+---
+
+<!--
+Replace this comment with a description of what the feature should do.
+Include details such as links to relevant specs or previous discussions.
+-->
+
+<!--
+Replace this comment with an example of the problem which this feature
+would resolve. Is this problem solvable without changes to Flask, such
+as by subclassing or using an extension?
+-->

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,16 +0,0 @@
-Describe what this patch does to fix the issue.
-
-Link to any relevant issues or pull requests.
-
-<!--
-Commit checklist:
-
-* add tests that fail without the patch
-* ensure all tests pass with ``pytest``
-* add documentation to the relevant docstrings or pages
-* add ``versionadded`` or ``versionchanged`` directives to relevant docstrings
-* add a changelog entry if this patch changes code
-
-Tests, coverage, and docs will be run automatically when you submit the pull
-request, but running them yourself can save time.
--->

.github/pull_request_template.md

@@ -0,0 +1,25 @@
+<!--
+Before opening a PR, open a ticket describing the issue or feature the
+PR will address. An issue is not required for fixing typos in
+documentation, or other simple non-code changes.
+
+Replace this comment with a description of the change. Describe how it
+addresses the linked ticket.
+-->
+
+<!--
+Link to relevant issues or previous PRs, one per line. Use "fixes" to
+automatically close an issue.
+
+fixes #<issue number>
+-->
+
+<!--
+Ensure each step in CONTRIBUTING.rst is complete, especially the following:
+
+- Add tests that demonstrate the correct behavior of the change. Tests
+  should fail without the change.
+- Add or update relevant docs, in the docs folder and in code.
+- Add an entry in CHANGES.rst summarizing the change and linking to the issue.
+- Add `.. versionchanged::` entries in any relevant code docs.
+-->

.github/workflows/lock.yaml

@@ -0,0 +1,26 @@
+name: Lock inactive closed issues
+# Lock closed issues that have not received any further activity for two weeks.
+# This does not close open issues, only humans may do that. It is easier to
+# respond to new issues with fresh examples rather than continuing discussions
+# on old issues.
+
+on:
+  schedule:
+    - cron: '0 0 * * *'
+permissions: {}
+concurrency:
+  group: lock
+  cancel-in-progress: true
+jobs:
+  lock:
+    runs-on: ubuntu-latest
+    permissions:
+      issues: write
+      pull-requests: write
+      discussions: write
+    steps:
+      - uses: dessant/lock-threads@7266a7ce5c1df01b1c6db85bf8cd86c737dadbe7 # v6.0.0
+        with:
+          issue-inactive-days: 14
+          pr-inactive-days: 14
+          discussion-inactive-days: 14

.github/workflows/pre-commit.yaml

@@ -0,0 +1,29 @@
+name: pre-commit
+on:
+  pull_request:
+  push:
+    branches: [main, stable]
+permissions: {}
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+jobs:
+  main:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - uses: astral-sh/setup-uv@cec208311dfd045dd5311c1add060b2062131d57 # v8.0.0
+        with:
+          enable-cache: true
+          prune-cache: false
+      - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
+        id: setup-python
+        with:
+          python-version-file: pyproject.toml
+      - uses: actions/cache@668228422ae6a00e4ad889ee87cd7109ec5666a7 # v5.0.4
+        with:
+          path: ~/.cache/pre-commit
+          key: pre-commit|${{ hashFiles('pyproject.toml', '.pre-commit-config.yaml') }}
+      - run: uv run --locked --no-default-groups --group pre-commit pre-commit run --show-diff-on-failure --color=always --all-files

.github/workflows/publish.yaml

@@ -0,0 +1,62 @@
+name: Publish
+on:
+  push:
+    tags: ['*']
+permissions: {}
+concurrency:
+  group: publish-${{ github.event.push.ref }}
+  cancel-in-progress: true
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    outputs:
+      artifact-id: ${{ steps.upload-artifact.outputs.artifact-id }}
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - uses: astral-sh/setup-uv@cec208311dfd045dd5311c1add060b2062131d57 # v8.0.0
+        with:
+          enable-cache: false
+          prune-cache: false
+      - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
+        with:
+          python-version-file: pyproject.toml
+      - run: echo "SOURCE_DATE_EPOCH=$(git log -1 --pretty=%ct)" >> $GITHUB_ENV
+      - run: uv build
+      - uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
+        id: upload-artifact
+        with:
+          name: dist
+          path: dist/
+          if-no-files-found: error
+  create-release:
+    needs: [build]
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          artifact-ids: ${{ needs.build.outputs.artifact-id }}
+          path: dist/
+      - name: create release
+        run: gh release create --draft --repo ${GITHUB_REPOSITORY} ${GITHUB_REF_NAME} dist/*
+        env:
+          GH_TOKEN: ${{ github.token }}
+  publish-pypi:
+    needs: [build]
+    environment:
+      name: publish
+      url: https://pypi.org/project/Flask/${{ github.ref_name }}
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+    steps:
+      - uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
+        with:
+          artifact-ids: ${{ needs.build.outputs.artifact-id }}
+          path: dist/
+      - uses: pypa/gh-action-pypi-publish@ed0c53931b1dc9bd32cbe73a98c7f6766f8a527e # v1.13.0
+        with:
+          packages-dir: "dist/"

.github/workflows/tests.yaml

@@ -0,0 +1,63 @@
+name: Tests
+on:
+  pull_request:
+    paths-ignore: ['docs/**', 'README.md']
+  push:
+    branches: [main, stable]
+    paths-ignore: ['docs/**', 'README.md']
+permissions: {}
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+jobs:
+  tests:
+    name: ${{ matrix.name || matrix.python }}
+    runs-on: ${{ matrix.os || 'ubuntu-latest' }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - {python: '3.14'}
+          - {python: '3.14t'}
+          - {name: Windows, python: '3.14', os: windows-latest}
+          - {name: Mac, python: '3.14', os: macos-latest}
+          - {python: '3.13'}
+          - {python: '3.12'}
+          - {python: '3.11'}
+          - {python: '3.10'}
+          - {name: PyPy, python: 'pypy-3.11', tox: pypy3.11}
+          - {name: Minimum Versions, python: '3.14', tox: tests-min}
+          - {name: Development Versions, python: '3.10', tox: tests-dev}
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - uses: astral-sh/setup-uv@cec208311dfd045dd5311c1add060b2062131d57 # v8.0.0
+        with:
+          enable-cache: true
+          prune-cache: false
+      - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
+        with:
+          python-version: ${{ matrix.python }}
+      - run: uv run --locked --no-default-groups --group dev tox run
+        env:
+          TOX_ENV: ${{ matrix.tox || format('py{0}', matrix.python) }}
+  typing:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - uses: astral-sh/setup-uv@cec208311dfd045dd5311c1add060b2062131d57 # v8.0.0
+        with:
+          enable-cache: true
+          prune-cache: false
+      - uses: actions/setup-python@a309ff8b426b58ec0e2a45f0f869d46889d02405 # v6.2.0
+        with:
+          python-version-file: pyproject.toml
+      - name: cache mypy
+        uses: actions/cache@668228422ae6a00e4ad889ee87cd7109ec5666a7 # v5.0.4
+        with:
+          path: ./.mypy_cache
+          key: mypy|${{ hashFiles('pyproject.toml') }}
+      - run: uv run --locked --no-default-groups --group dev tox run -e typing

.github/workflows/zizmor.yaml

@@ -0,0 +1,22 @@
+name: GitHub Actions security analysis with zizmor
+on:
+  pull_request:
+    paths: ["**/*.yaml?"]
+  push:
+    branches: [main, stable]
+    paths: ["**/*.yaml?"]
+permissions: {}
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+jobs:
+  zizmor:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - uses: zizmorcore/zizmor-action@71321a20a9ded102f6e9ce5718a2fcec2c4f70d8 # v0.5.2
+        with:
+          advanced-security: false
+          annotations: true

.gitignore

@@ -1,23 +1,8 @@
-.DS_Store
-.env
-.flaskenv
-*.pyc
-*.pyo
-env/
-env*
-dist/
-build/
-*.egg
-*.egg-info/
-_mailinglist
-.tox/
-.cache/
-.pytest_cache/
 .idea/
-docs/_build/
-
-# Coverage reports
+.vscode/
+__pycache__/
+dist/
+.coverage*
 htmlcov/
-.coverage
-.coverage.*
-*,cover
+.tox/
+docs/_build/

.pre-commit-config.yaml

@@ -0,0 +1,23 @@
+repos:
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: 5e2fb545eba1ea9dc051f6f962d52fe8f76a9794  # frozen: v0.15.13
+    hooks:
+      - id: ruff-check
+      - id: ruff-format
+  - repo: https://github.com/astral-sh/uv-pre-commit
+    rev: fa60a193803535a9e2accdb3ca4b1b584b1150cb  # frozen: 0.11.15
+    hooks:
+      - id: uv-lock
+  - repo: https://github.com/codespell-project/codespell
+    rev: 2ccb47ff45ad361a21071a7eedda4c37e6ae8c5a  # frozen: v2.4.2
+    hooks:
+      - id: codespell
+        args: ['--write-changes']
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: 3e8a8703264a2f4a69428a0aa4dcb512790b2c8c  # frozen: v6.0.0
+    hooks:
+      - id: check-merge-conflict
+      - id: debug-statements
+      - id: fix-byte-order-marker
+      - id: trailing-whitespace
+      - id: end-of-file-fixer

.readthedocs.yaml

@@ -0,0 +1,10 @@
+version: 2
+build:
+  os: ubuntu-24.04
+  tools:
+    python: '3.13'
+  commands:
+    - asdf plugin add uv
+    - asdf install uv latest
+    - asdf global uv latest
+    - uv run --group docs sphinx-build -W -b dirhtml docs $READTHEDOCS_OUTPUT/html

CONTRIBUTING.rst

@@ -1,184 +0,0 @@
-How to contribute to Flask
-==========================
-
-Thank you for considering contributing to Flask!
-
-Support questions
------------------
-
-Please, don't use the issue tracker for this. Use one of the following
-resources for questions about your own code:
-
-* The ``#get-help`` channel on our Discord chat: https://discordapp.com/invite/t6rrQZH
-
-  * The IRC channel ``#pocoo`` on FreeNode is linked to Discord, but
-    Discord is preferred.
-
-* The mailing list flask@python.org for long term discussion or larger issues.
-* Ask on `Stack Overflow`_. Search with Google first using:
-  ``site:stackoverflow.com flask {search term, exception message, etc.}``
-
-.. _Stack Overflow: https://stackoverflow.com/questions/tagged/flask?sort=linked
-
-Reporting issues
-----------------
-
-- Describe what you expected to happen.
-- If possible, include a `minimal reproducible example`_ to help us
-  identify the issue. This also helps check that the issue is not with
-  your own code.
-- Describe what actually happened. Include the full traceback if there was an
-  exception.
-- List your Python, Flask, and Werkzeug versions. If possible, check if this
-  issue is already fixed in the repository.
-
-.. _minimal reproducible example: https://stackoverflow.com/help/minimal-reproducible-example
-
-Submitting patches
-------------------
-
-- Include tests if your patch is supposed to solve a bug, and explain
-  clearly under which circumstances the bug happens. Make sure the test fails
-  without your patch.
-- Try to follow `PEP8`_, but you may ignore the line length limit if following
-  it would make the code uglier.
-
-First time setup
-~~~~~~~~~~~~~~~~
-
-- Download and install the `latest version of git`_.
-- Configure git with your `username`_ and `email`_::
-
-        git config --global user.name 'your name'
-        git config --global user.email 'your email'
-
-- Make sure you have a `GitHub account`_.
-- Fork Flask to your GitHub account by clicking the `Fork`_ button.
-- `Clone`_ your GitHub fork locally::
-
-        git clone https://github.com/{username}/flask
-        cd flask
-
-- Add the main repository as a remote to update later::
-
-        git remote add pallets https://github.com/pallets/flask
-        git fetch pallets
-
-- Create a virtualenv::
-
-        python3 -m venv env
-        . env/bin/activate
-        # or "env\Scripts\activate" on Windows
-
-- Install Flask in editable mode with development dependencies::
-
-        pip install -e ".[dev]"
-
-.. _GitHub account: https://github.com/join
-.. _latest version of git: https://git-scm.com/downloads
-.. _username: https://help.github.com/en/articles/setting-your-username-in-git
-.. _email: https://help.github.com/en/articles/setting-your-commit-email-address-in-git
-.. _Fork: https://github.com/pallets/flask/fork
-.. _Clone: https://help.github.com/en/articles/fork-a-repo#step-2-create-a-local-clone-of-your-fork
-
-Start coding
-~~~~~~~~~~~~
-
--   Create a branch to identify the issue you would like to work on. If
-    you're submitting a bug or documentation fix, branch off of the
-    latest ".x" branch::
-
-        git checkout -b your-branch-name origin/1.0.x
-
-    If you're submitting a feature addition or change, branch off of the
-    "master" branch::
-
-        git checkout -b your-branch-name origin/master
-
-- Using your favorite editor, make your changes, `committing as you go`_.
-- Try to follow `PEP8`_. We have a pre-commit config and tests that will
-  ensure the code follows our style guide.
-- Include tests that cover any code changes you make. Make sure the test fails
-  without your patch. `Run the tests. <contributing-testsuite_>`_.
-- Push your commits to GitHub and `create a pull request`_ by using::
-
-        git push --set-upstream origin your-branch-name
-
-- Celebrate 🎉
-
-.. _committing as you go: https://dont-be-afraid-to-commit.readthedocs.io/en/latest/git/commandlinegit.html#commit-your-changes
-.. _PEP8: https://pep8.org/
-.. _create a pull request: https://help.github.com/en/articles/creating-a-pull-request
-
-.. _contributing-testsuite:
-
-Running the tests
-~~~~~~~~~~~~~~~~~
-
-Run the basic test suite with::
-
-    pytest
-
-This only runs the tests for the current environment. Whether this is relevant
-depends on which part of Flask you're working on. Travis-CI will run the full
-suite when you submit your pull request.
-
-The full test suite takes a long time to run because it tests multiple
-combinations of Python and dependencies. You need to have Python 2.7, 3.4,
-3.5 3.6, and PyPy 2.7 installed to run all of the environments. Then run::
-
-    tox
-
-Running test coverage
-~~~~~~~~~~~~~~~~~~~~~
-
-Generating a report of lines that do not have test coverage can indicate
-where to start contributing. Run ``pytest`` using ``coverage`` and generate a
-report on the terminal and as an interactive HTML document::
-
-    coverage run -m pytest
-    coverage report
-    coverage html
-    # then open htmlcov/index.html
-
-Read more about `coverage <https://coverage.readthedocs.io>`_.
-
-Running the full test suite with ``tox`` will combine the coverage reports
-from all runs.
-
-
-Building the docs
-~~~~~~~~~~~~~~~~~
-
-Build the docs in the ``docs`` directory using Sphinx::
-
-    cd docs
-    make html
-
-Open ``_build/html/index.html`` in your browser to view the docs.
-
-Read more about `Sphinx <https://www.sphinx-doc.org/en/master/>`_.
-
-
-Caution: zero-padded file modes
--------------------------------
-
-This repository contains several zero-padded file modes that may cause issues
-when pushing this repository to git hosts other than GitHub. Fixing this is
-destructive to the commit history, so we suggest ignoring these warnings. If it
-fails to push and you're using a self-hosted git service like GitLab, you can
-turn off repository checks in the admin panel.
-
-These files can also cause issues while cloning. If you have ::
-
-    [fetch]
-    fsckobjects = true
-
-or ::
-
-    [receive]
-    fsckObjects = true
-
-set in your git configuration file, cloning this repository will fail. The only
-solution is to set both of the above settings to false while cloning, and then
-setting them back to true after the cloning is finished.

MANIFEST.in

@@ -1,8 +0,0 @@
-include CHANGES.rst
-include CONTRIBUTING.rst
-include tox.ini
-graft artwork
-graft docs
-prune docs/_build
-graft examples
-graft tests

README.md

@@ -0,0 +1,53 @@
+<div align="center"><img src="https://raw.githubusercontent.com/pallets/flask/refs/heads/stable/docs/_static/flask-name.svg" alt="" height="150"></div>
+
+# Flask
+
+Flask is a lightweight [WSGI] web application framework. It is designed
+to make getting started quick and easy, with the ability to scale up to
+complex applications. It began as a simple wrapper around [Werkzeug]
+and [Jinja], and has become one of the most popular Python web
+application frameworks.
+
+Flask offers suggestions, but doesn't enforce any dependencies or
+project layout. It is up to the developer to choose the tools and
+libraries they want to use. There are many extensions provided by the
+community that make adding new functionality easy.
+
+[WSGI]: https://wsgi.readthedocs.io/
+[Werkzeug]: https://werkzeug.palletsprojects.com/
+[Jinja]: https://jinja.palletsprojects.com/
+
+## A Simple Example
+
+```python
+# save this as app.py
+from flask import Flask
+
+app = Flask(__name__)
+
+@app.route("/")
+def hello():
+    return "Hello, World!"
+```
+
+```
+$ flask run
+  * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
+```
+
+## Donate
+
+The Pallets organization develops and supports Flask and the libraries
+it uses. In order to grow the community of contributors and users, and
+allow the maintainers to devote more time to the projects, [please
+donate today].
+
+[please donate today]: https://palletsprojects.com/donate
+
+## Contributing
+
+See our [detailed contributing documentation][contrib] for many ways to
+contribute, including reporting issues, requesting features, asking or answering
+questions, and making PRs.
+
+[contrib]: https://palletsprojects.com/contributing/

README.rst

@@ -1,71 +0,0 @@
-Flask
-=====
-
-Flask is a lightweight `WSGI`_ web application framework. It is designed
-to make getting started quick and easy, with the ability to scale up to
-complex applications. It began as a simple wrapper around `Werkzeug`_
-and `Jinja`_ and has become one of the most popular Python web
-application frameworks.
-
-Flask offers suggestions, but doesn't enforce any dependencies or
-project layout. It is up to the developer to choose the tools and
-libraries they want to use. There are many extensions provided by the
-community that make adding new functionality easy.
-
-
-Installing
-----------
-
-Install and update using `pip`_:
-
-.. code-block:: text
-
-    pip install -U Flask
-
-
-A Simple Example
-----------------
-
-.. code-block:: python
-
-    from flask import Flask
-
-    app = Flask(__name__)
-
-    @app.route("/")
-    def hello():
-        return "Hello, World!"
-
-.. code-block:: text
-
-    $ FLASK_APP=hello.py flask run
-     * Serving Flask app "hello"
-     * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
-
-
-Donate
-------
-
-The Pallets organization develops and supports Flask and the libraries
-it uses. In order to grow the community of contributors and users, and
-allow the maintainers to devote more time to the projects, `please
-donate today`_.
-
-.. _please donate today: https://psfmember.org/civicrm/contribute/transact?reset=1&id=20
-
-
-Links
------
-
-* Website: https://www.palletsprojects.com/p/flask/
-* Documentation: http://flask.pocoo.org/docs/
-* Releases: https://pypi.org/project/Flask/
-* Code: https://github.com/pallets/flask
-* Issue tracker: https://github.com/pallets/flask/issues
-* Test status: https://dev.azure.com/pallets/flask/_build
-* Official chat: https://discord.gg/t6rrQZH
-
-.. _WSGI: https://wsgi.readthedocs.io
-.. _Werkzeug: https://www.palletsprojects.com/p/werkzeug/
-.. _Jinja: https://www.palletsprojects.com/p/jinja/
-.. _pip: https://pip.pypa.io/en/stable/quickstart/

artwork/LICENSE.rst

@@ -1,19 +0,0 @@
-Copyright 2010 Pallets
-
-This logo or a modified version may be used by anyone to refer to the
-Flask project, but does not indicate endorsement by the project.
-
-Redistribution and use in source (SVG) and binary (renders in PNG, etc.)
-forms, with or without modification, are permitted provided that the
-following conditions are met:
-
-1.  Redistributions of source code must retain the above copyright
-    notice and this list of conditions.
-
-3.  Neither the name of the copyright holder nor the names of its
-    contributors may be used to endorse or promote products derived from
-    this software without specific prior written permission.
-
-We would appreciate that you make the image a link to
-https://palletsprojects.com/p/flask/ if you use it in a medium that
-supports links.

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docs/_static/flask-name.svg

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docs/advanced_foreword.rst

@@ -1,47 +0,0 @@
-.. _advanced_foreword:
-
-Foreword for Experienced Programmers
-====================================
-
-Thread-Locals in Flask
-----------------------
-
-One of the design decisions in Flask was that simple tasks should be simple;
-they should not take a lot of code and yet they should not limit you. Because
-of that, Flask has a few design choices that some people might find surprising or
-unorthodox. For example, Flask uses thread-local objects internally so that you
-don’t have to pass objects around from function to function within a request in
-order to stay threadsafe. This approach is convenient, but requires a valid
-request context for dependency injection or when attempting to reuse code which
-uses a value pegged to the request.  The Flask project is honest about
-thread-locals, does not hide them, and calls out in the code and documentation
-where they are used.
-
-Develop for the Web with Caution
---------------------------------
-
-Always keep security in mind when building web applications.
-
-If you write a web application, you are probably allowing users to register
-and leave their data on your server.  The users are entrusting you with data.
-And even if you are the only user that might leave data in your application,
-you still want that data to be stored securely.
-
-Unfortunately, there are many ways the security of a web application can be
-compromised.  Flask protects you against one of the most common security
-problems of modern web applications: cross-site scripting (XSS).  Unless you
-deliberately mark insecure HTML as secure, Flask and the underlying Jinja2
-template engine have you covered.  But there are many more ways to cause
-security problems.
-
-The documentation will warn you about aspects of web development that require
-attention to security.  Some of these security concerns are far more complex
-than one might think, and we all sometimes underestimate the likelihood that a
-vulnerability will be exploited - until a clever attacker figures out a way to
-exploit our applications.  And don't think that your application is not
-important enough to attract an attacker.  Depending on the kind of attack,
-chances are that automated bots are probing for ways to fill your database with
-spam, links to malicious software, and the like.
-
-Flask is no different from any other framework in that you the developer must
-build with caution, watching for exploits when building to your requirements.

docs/api.rst

@@ -1,11 +1,9 @@
-.. _api:
-
 API
 ===
 
 .. module:: flask
 
-This part of the documentation covers all the interfaces of Flask.  For
+This part of the documentation covers all the interfaces of Flask. For
 parts where Flask depends on external libraries, we document the most
 important right here and provide links to the canonical documentation.
 
@@ -29,76 +27,28 @@ Incoming Request Data
 ---------------------
 
 .. autoclass:: Request
-   :members:
-   :inherited-members:
+    :members:
+    :inherited-members:
+    :exclude-members: json_module
 
-   .. attribute:: environ
+.. data:: request
 
-      The underlying WSGI environment.
+    A proxy to the request data for the current request, an instance of
+    :class:`.Request`.
 
-   .. attribute:: path
-   .. attribute:: full_path
-   .. attribute:: script_root
-   .. attribute:: url
-   .. attribute:: base_url
-   .. attribute:: url_root
+    This is only available when a :doc:`request context </appcontext>` is
+    active.
 
-      Provides different ways to look at the current :rfc:`3987`.
-      Imagine your application is listening on the following application
-      root::
-
-          http://www.example.com/myapplication
-
-      And a user requests the following URI::
-
-          http://www.example.com/myapplication/%CF%80/page.html?x=y
-
-      In this case the values of the above mentioned attributes would be
-      the following:
-
-      ============= ======================================================
-      `path`        ``u'/π/page.html'``
-      `full_path`   ``u'/π/page.html?x=y'``
-      `script_root` ``u'/myapplication'``
-      `base_url`    ``u'http://www.example.com/myapplication/π/page.html'``
-      `url`         ``u'http://www.example.com/myapplication/π/page.html?x=y'``
-      `url_root`    ``u'http://www.example.com/myapplication/'``
-      ============= ======================================================
-
-
-.. attribute:: request
-
-   To access incoming request data, you can use the global `request`
-   object.  Flask parses incoming request data for you and gives you
-   access to it through that global object.  Internally Flask makes
-   sure that you always get the correct data for the active thread if you
-   are in a multithreaded environment.
-
-   This is a proxy.  See :ref:`notes-on-proxies` for more information.
-
-   The request object is an instance of a :class:`~werkzeug.wrappers.Request`
-   subclass and provides all of the attributes Werkzeug defines.  This
-   just shows a quick overview of the most important ones.
+    This is a proxy. See :ref:`context-visibility` for more information.
 
 
 Response Objects
 ----------------
 
 .. autoclass:: flask.Response
-   :members: set_cookie, max_cookie_size, data, mimetype, is_json, get_json
-
-   .. attribute:: headers
-
-      A :class:`~werkzeug.datastructures.Headers` object representing the response headers.
-
-   .. attribute:: status
-
-      A string with a response status.
-
-   .. attribute:: status_code
-
-      The response status as integer.
-
+    :members:
+    :inherited-members:
+    :exclude-members: json_module
 
 Sessions
 --------
@@ -110,40 +60,33 @@ does this is by using a signed cookie. The user can look at the session
 contents, but can't modify it unless they know the secret key, so make sure to
 set that to something complex and unguessable.
 
-To access the current session you can use the :class:`session` object:
+To access the current session you can use the :data:`.session` proxy.
 
-.. class:: session
+.. data:: session
 
-   The session object works pretty much like an ordinary dict, with the
-   difference that it keeps track on modifications.
+    A proxy to the session data for the current request, an instance of
+    :class:`.SessionMixin`.
 
-   This is a proxy.  See :ref:`notes-on-proxies` for more information.
+    This is only available when a :doc:`request context </appcontext>` is
+    active.
 
-   The following attributes are interesting:
+    This is a proxy. See :ref:`context-visibility` for more information.
 
-   .. attribute:: new
+    The session object works like a dict but tracks assignment and access to its
+    keys. It cannot track modifications to mutable values, you need to set
+    :attr:`~.SessionMixin.modified` manually when modifying a list, dict, etc.
 
-      ``True`` if the session is new, ``False`` otherwise.
+    .. code-block:: python
 
-   .. attribute:: modified
-
-      ``True`` if the session object detected a modification.  Be advised
-      that modifications on mutable structures are not picked up
-      automatically, in that situation you have to explicitly set the
-      attribute to ``True`` yourself.  Here an example::
-
-          # this change is not picked up because a mutable object (here
-          # a list) is changed.
-          session['objects'].append(42)
+          # appending to a list is not detected
+          session["numbers"].append(42)
           # so mark it as modified yourself
           session.modified = True
 
-   .. attribute:: permanent
-
-      If set to ``True`` the session lives for
-      :attr:`~flask.Flask.permanent_session_lifetime` seconds.  The
-      default is 31 days.  If set to ``False`` (which is the default) the
-      session will be deleted when the user closes the browser.
+    The session is persisted across requests using a cookie. By default the
+    users's browser will clear the cookie when it is closed. Set
+    :attr:`~.SessionMixin.permanent` to ``True`` to persist the cookie for
+    :data:`PERMANENT_SESSION_LIFETIME`.
 
 
 Session Interface
@@ -173,10 +116,9 @@ implementation that Flask is using.
 
 .. admonition:: Notice
 
-   The ``PERMANENT_SESSION_LIFETIME`` config key can also be an integer
-   starting with Flask 0.8.  Either catch this down yourself or use
-   the :attr:`~flask.Flask.permanent_session_lifetime` attribute on the
-   app which converts the result to an integer automatically.
+    The :data:`PERMANENT_SESSION_LIFETIME` config can be an integer or ``timedelta``.
+    The :attr:`~flask.Flask.permanent_session_lifetime` attribute is always a
+    ``timedelta``.
 
 
 Test Client
@@ -204,23 +146,24 @@ Application Globals
 
 To share data that is valid for one request only from one function to
 another, a global variable is not good enough because it would break in
-threaded environments.  Flask provides you with a special object that
+threaded environments. Flask provides you with a special object that
 ensures it is only valid for the active request and that will return
-different values for each request.  In a nutshell: it does the right
-thing, like it does for :class:`request` and :class:`session`.
+different values for each request. In a nutshell: it does the right
+thing, like it does for :data:`.request` and :data:`.session`.
 
 .. data:: g
 
-    A namespace object that can store data during an
-    :doc:`application context </appcontext>`. This is an instance of
-    :attr:`Flask.app_ctx_globals_class`, which defaults to
-    :class:`ctx._AppCtxGlobals`.
+    A proxy to a namespace object used to store data during a single request or
+    app context. An instance of :attr:`.Flask.app_ctx_globals_class`, which
+    defaults to :class:`._AppCtxGlobals`.
 
-    This is a good place to store resources during a request. During
-    testing, you can use the :ref:`faking-resources` pattern to
-    pre-configure such resources.
+    This is a good place to store resources during a request. For example, a
+    :meth:`~.Flask.before_request` function could load a user object from a
+    session id, then set ``g.user`` to be used in the view function.
 
-    This is a proxy. See :ref:`notes-on-proxies` for more information.
+    This is only available when an :doc:`app context </appcontext>` is active.
+
+    This is a proxy. See :ref:`context-visibility` for more information.
 
     .. versionchanged:: 0.10
         Bound to the application context instead of the request context.
@@ -234,17 +177,16 @@ Useful Functions and Classes
 
 .. data:: current_app
 
-    A proxy to the application handling the current request. This is
-    useful to access the application without needing to import it, or if
-    it can't be imported, such as when using the application factory
-    pattern or in blueprints and extensions.
+    A proxy to the :class:`.Flask` application handling the current request or
+    other activity.
 
-    This is only available when an
-    :doc:`application context </appcontext>` is pushed. This happens
-    automatically during requests and CLI commands. It can be controlled
-    manually with :meth:`~flask.Flask.app_context`.
+    This is useful to access the application without needing to import it, or if
+    it can't be imported, such as when using the application factory pattern or
+    in blueprints and extensions.
 
-    This is a proxy. See :ref:`notes-on-proxies` for more information.
+    This is only available when an :doc:`app context </appcontext>` is active.
+
+    This is a proxy. See :ref:`context-visibility` for more information.
 
 .. autofunction:: has_request_context
 
@@ -266,12 +208,6 @@ Useful Functions and Classes
 
 .. autofunction:: send_from_directory
 
-.. autofunction:: safe_join
-
-.. autofunction:: escape
-
-.. autoclass:: Markup
-   :members: escape, unescape, striptags
 
 Message Flashing
 ----------------
@@ -280,58 +216,29 @@ Message Flashing
 
 .. autofunction:: get_flashed_messages
 
+
 JSON Support
 ------------
 
 .. module:: flask.json
 
-Flask uses ``simplejson`` for the JSON implementation.  Since simplejson
-is provided by both the standard library as well as extension, Flask will
-try simplejson first and then fall back to the stdlib json module.  On top
-of that it will delegate access to the current application's JSON encoders
-and decoders for easier customization.
+Flask uses Python's built-in :mod:`json` module for handling JSON by
+default. The JSON implementation can be changed by assigning a different
+provider to :attr:`flask.Flask.json_provider_class` or
+:attr:`flask.Flask.json`. The functions provided by ``flask.json`` will
+use methods on ``app.json`` if an app context is active.
 
-So for starters instead of doing::
-
-    try:
-        import simplejson as json
-    except ImportError:
-        import json
-
-You can instead just do this::
-
-    from flask import json
-
-For usage examples, read the :mod:`json` documentation in the standard
-library.  The following extensions are by default applied to the stdlib's
-JSON module:
-
-1.  ``datetime`` objects are serialized as :rfc:`822` strings.
-2.  Any object with an ``__html__`` method (like :class:`~flask.Markup`)
-    will have that method called and then the return value is serialized
-    as string.
-
-The :func:`~htmlsafe_dumps` function of this json module is also available
-as a filter called ``|tojson`` in Jinja2.  Note that in versions of Flask prior
-to Flask 0.10, you must disable escaping with ``|safe`` if you intend to use
-``|tojson`` output inside ``script`` tags. In Flask 0.10 and above, this
-happens automatically (but it's harmless to include ``|safe`` anyway).
+Jinja's ``|tojson`` filter is configured to use the app's JSON provider.
+The filter marks the output with ``|safe``. Use it to render data inside
+HTML ``<script>`` tags.
 
 .. sourcecode:: html+jinja
 
-    <script type=text/javascript>
-        doSomethingWith({{ user.username|tojson|safe }});
+    <script>
+        const names = {{ names|tojson }};
+        renderChart(names, {{ axis_data|tojson }});
     </script>
 
-.. admonition:: Auto-Sort JSON Keys
-
-    The configuration variable ``JSON_SORT_KEYS`` (:ref:`config`) can be
-    set to false to stop Flask from auto-sorting keys.  By default sorting
-    is enabled and outside of the app context sorting is turned on.
-
-    Notice that disabling key sorting can cause issues when using content
-    based HTTP caches and Python's hash randomization feature.
-
 .. autofunction:: jsonify
 
 .. autofunction:: dumps
@@ -342,14 +249,17 @@ happens automatically (but it's harmless to include ``|safe`` anyway).
 
 .. autofunction:: load
 
-.. autoclass:: JSONEncoder
-   :members:
+.. autoclass:: flask.json.provider.JSONProvider
+    :members:
+    :member-order: bysource
 
-.. autoclass:: JSONDecoder
-   :members:
+.. autoclass:: flask.json.provider.DefaultJSONProvider
+    :members:
+    :member-order: bysource
 
 .. automodule:: flask.json.tag
 
+
 Template Rendering
 ------------------
 
@@ -359,6 +269,10 @@ Template Rendering
 
 .. autofunction:: render_template_string
 
+.. autofunction:: stream_template
+
+.. autofunction:: stream_template_string
+
 .. autofunction:: get_template_attribute
 
 Configuration
@@ -376,59 +290,31 @@ Stream Helpers
 Useful Internals
 ----------------
 
-.. autoclass:: flask.ctx.RequestContext
-   :members:
-
-.. data:: _request_ctx_stack
-
-    The internal :class:`~werkzeug.local.LocalStack` that holds
-    :class:`~flask.ctx.RequestContext` instances. Typically, the
-    :data:`request` and :data:`session` proxies should be accessed
-    instead of the stack. It may be useful to access the stack in
-    extension code.
-
-    The following attributes are always present on each layer of the
-    stack:
-
-    `app`
-      the active Flask application.
-
-    `url_adapter`
-      the URL adapter that was used to match the request.
-
-    `request`
-      the current request object.
-
-    `session`
-      the active session object.
-
-    `g`
-      an object with all the attributes of the :data:`flask.g` object.
-
-    `flashes`
-      an internal cache for the flashed messages.
-
-    Example usage::
-
-        from flask import _request_ctx_stack
-
-        def get_session():
-            ctx = _request_ctx_stack.top
-            if ctx is not None:
-                return ctx.session
-
 .. autoclass:: flask.ctx.AppContext
    :members:
 
-.. data:: _app_ctx_stack
+.. data:: flask.globals.app_ctx
 
-    The internal :class:`~werkzeug.local.LocalStack` that holds
-    :class:`~flask.ctx.AppContext` instances. Typically, the
-    :data:`current_app` and :data:`g` proxies should be accessed instead
-    of the stack. Extensions can access the contexts on the stack as a
-    namespace to store data.
+    A proxy to the active :class:`.AppContext`.
 
-    .. versionadded:: 0.9
+    This is an internal object that is essential to how Flask handles requests.
+    Accessing this should not be needed in most cases. Most likely you want
+    :data:`.current_app`, :data:`.g`, :data:`.request`, and :data:`.session` instead.
+
+    This is only available when a :doc:`request context </appcontext>` is
+    active.
+
+    This is a proxy. See :ref:`context-visibility` for more information.
+
+.. class:: flask.ctx.RequestContext
+
+    .. deprecated:: 3.2
+        Merged with :class:`AppContext`. This alias will be removed in Flask 4.0.
+
+.. data:: flask.globals.request_ctx
+
+    .. deprecated:: 3.2
+        Merged with :data:`.app_ctx`. This alias will be removed in Flask 4.0.
 
 .. autoclass:: flask.blueprints.BlueprintSetupState
    :members:
@@ -438,18 +324,13 @@ Useful Internals
 Signals
 -------
 
-.. versionadded:: 0.6
+Signals are provided by the `Blinker`_ library. See :doc:`signals` for an introduction.
 
-.. data:: signals.signals_available
-
-   ``True`` if the signaling system is available.  This is the case
-   when `blinker`_ is installed.
-
-The following signals exist in Flask:
+.. _blinker: https://blinker.readthedocs.io/
 
 .. data:: template_rendered
 
-   This signal is sent when a template was successfully rendered.  The
+   This signal is sent when a template was successfully rendered. The
    signal is invoked with the instance of the template as `template`
    and the context as dictionary (named `context`).
 
@@ -483,7 +364,7 @@ The following signals exist in Flask:
 .. data:: request_started
 
    This signal is sent when the request context is set up, before
-   any request processing happens.  Because the request context is already
+   any request processing happens. Because the request context is already
    bound, the subscriber can access the request with the standard global
    proxies such as :class:`~flask.request`.
 
@@ -503,7 +384,7 @@ The following signals exist in Flask:
    Example subscriber::
 
         def log_response(sender, response, **extra):
-            sender.logger.debug('Request context is about to close down.  '
+            sender.logger.debug('Request context is about to close down. '
                                 'Response: %s', response)
 
         from flask import request_finished
@@ -511,23 +392,37 @@ The following signals exist in Flask:
 
 .. data:: got_request_exception
 
-   This signal is sent when an exception happens during request processing.
-   It is sent *before* the standard exception handling kicks in and even
-   in debug mode, where no exception handling happens.  The exception
-   itself is passed to the subscriber as `exception`.
+    This signal is sent when an unhandled exception happens during
+    request processing, including when debugging. The exception is
+    passed to the subscriber as ``exception``.
 
-   Example subscriber::
+    This signal is not sent for
+    :exc:`~werkzeug.exceptions.HTTPException`, or other exceptions that
+    have error handlers registered, unless the exception was raised from
+    an error handler.
 
-        def log_exception(sender, exception, **extra):
-            sender.logger.debug('Got exception during processing: %s', exception)
+    This example shows how to do some extra logging if a theoretical
+    ``SecurityException`` was raised:
+
+    .. code-block:: python
 
         from flask import got_request_exception
-        got_request_exception.connect(log_exception, app)
+
+        def log_security_exception(sender, exception, **extra):
+            if not isinstance(exception, SecurityException):
+                return
+
+            security_logger.exception(
+                f"SecurityException at {request.url!r}",
+                exc_info=exception,
+            )
+
+        got_request_exception.connect(log_security_exception, app)
 
 .. data:: request_tearing_down
 
-   This signal is sent when the request is tearing down.  This is always
-   called, even if an exception is caused.  Currently functions listening
+   This signal is sent when the request is tearing down. This is always
+   called, even if an exception is caused. Currently functions listening
    to this signal are called after the regular teardown handlers, but this
    is not something you can rely on.
 
@@ -545,8 +440,8 @@ The following signals exist in Flask:
 
 .. data:: appcontext_tearing_down
 
-   This signal is sent when the app context is tearing down.  This is always
-   called, even if an exception is caused.  Currently functions listening
+   This signal is sent when the app context is tearing down. This is always
+   called, even if an exception is caused. Currently functions listening
    to this signal are called after the regular teardown handlers, but this
    is not something you can rely on.
 
@@ -563,9 +458,9 @@ The following signals exist in Flask:
 
 .. data:: appcontext_pushed
 
-   This signal is sent when an application context is pushed.  The sender
-   is the application.  This is usually useful for unittests in order to
-   temporarily hook in information.  For instance it can be used to
+   This signal is sent when an application context is pushed. The sender
+   is the application. This is usually useful for unittests in order to
+   temporarily hook in information. For instance it can be used to
    set a resource early onto the `g` object.
 
    Example usage::
@@ -592,16 +487,15 @@ The following signals exist in Flask:
 
 .. data:: appcontext_popped
 
-   This signal is sent when an application context is popped.  The sender
-   is the application.  This usually falls in line with the
+   This signal is sent when an application context is popped. The sender
+   is the application. This usually falls in line with the
    :data:`appcontext_tearing_down` signal.
 
    .. versionadded:: 0.10
 
-
 .. data:: message_flashed
 
-   This signal is sent when the application is flashing a message.  The
+   This signal is sent when the application is flashing a message. The
    messages is sent as `message` keyword argument and the category as
    `category`.
 
@@ -616,24 +510,6 @@ The following signals exist in Flask:
 
    .. versionadded:: 0.10
 
-.. class:: signals.Namespace
-
-   An alias for :class:`blinker.base.Namespace` if blinker is available,
-   otherwise a dummy class that creates fake signals.  This class is
-   available for Flask extensions that want to provide the same fallback
-   system as Flask itself.
-
-   .. method:: signal(name, doc=None)
-
-      Creates a new signal for this namespace if blinker is available,
-      otherwise returns a fake signal that has a send method that will
-      do nothing but will fail with a :exc:`RuntimeError` for all other
-      operations, including connecting.
-
-
-.. _blinker: https://pypi.org/project/blinker/
-
-.. _class-based-views:
 
 Class-Based Views
 -----------------
@@ -661,7 +537,7 @@ Generally there are three ways to define rules for the routing system:
     which is exposed as :attr:`flask.Flask.url_map`.
 
 Variable parts in the route can be specified with angular brackets
-(``/user/<username>``).  By default a variable part in the URL accepts any
+(``/user/<username>``). By default a variable part in the URL accepts any
 string without a slash however a different converter can be specified as
 well by using ``<converter:name>``.
 
@@ -695,7 +571,7 @@ Here are some examples::
         pass
 
 An important detail to keep in mind is how Flask deals with trailing
-slashes.  The idea is to keep each URL unique so the following rules
+slashes. The idea is to keep each URL unique so the following rules
 apply:
 
 1. If a rule ends with a slash and is requested without a slash by the
@@ -704,11 +580,11 @@ apply:
 2. If a rule does not end with a trailing slash and the user requests the
    page with a trailing slash, a 404 not found is raised.
 
-This is consistent with how web servers deal with static files.  This
+This is consistent with how web servers deal with static files. This
 also makes it possible to use relative link targets safely.
 
-You can also define multiple rules for the same function.  They have to be
-unique however.  Defaults can also be specified.  Here for example is a
+You can also define multiple rules for the same function. They have to be
+unique however. Defaults can also be specified. Here for example is a
 definition for a URL that accepts an optional page::
 
     @app.route('/users/', defaults={'page': 1})
@@ -720,7 +596,7 @@ This specifies that ``/users/`` will be the URL for page one and
 ``/users/page/N`` will be the URL for page ``N``.
 
 If a URL contains a default value, it will be redirected to its simpler
-form with a 301 redirect. In the above example, ``/users/page/1`` will
+form with a 308 redirect. In the above example, ``/users/page/1`` will
 be redirected to ``/users/``. If your route handles ``GET`` and ``POST``
 requests, make sure the default route only handles ``GET``, as redirects
 can't preserve form data. ::
@@ -731,36 +607,35 @@ can't preserve form data. ::
       pass
 
 Here are the parameters that :meth:`~flask.Flask.route` and
-:meth:`~flask.Flask.add_url_rule` accept.  The only difference is that
+:meth:`~flask.Flask.add_url_rule` accept. The only difference is that
 with the route parameter the view function is defined with the decorator
 instead of the `view_func` parameter.
 
 =============== ==========================================================
 `rule`          the URL rule as string
-`endpoint`      the endpoint for the registered URL rule.  Flask itself
+`endpoint`      the endpoint for the registered URL rule. Flask itself
                 assumes that the name of the view function is the name
                 of the endpoint if not explicitly stated.
 `view_func`     the function to call when serving a request to the
-                provided endpoint.  If this is not provided one can
+                provided endpoint. If this is not provided one can
                 specify the function later by storing it in the
                 :attr:`~flask.Flask.view_functions` dictionary with the
                 endpoint as key.
-`defaults`      A dictionary with defaults for this rule.  See the
+`defaults`      A dictionary with defaults for this rule. See the
                 example above for how defaults work.
 `subdomain`     specifies the rule for the subdomain in case subdomain
-                matching is in use.  If not specified the default
+                matching is in use. If not specified the default
                 subdomain is assumed.
 `**options`     the options to be forwarded to the underlying
-                :class:`~werkzeug.routing.Rule` object.  A change to
-                Werkzeug is handling of method options.  methods is a list
+                :class:`~werkzeug.routing.Rule` object. A change to
+                Werkzeug is handling of method options. methods is a list
                 of methods this rule should be limited to (``GET``, ``POST``
-                etc.).  By default a rule just listens for ``GET`` (and
-                implicitly ``HEAD``).  Starting with Flask 0.6, ``OPTIONS`` is
+                etc.). By default a rule just listens for ``GET`` (and
+                implicitly ``HEAD``). Starting with Flask 0.6, ``OPTIONS`` is
                 implicitly added and handled by the standard request
-                handling.  They have to be specified as keyword arguments.
+                handling. They have to be specified as keyword arguments.
 =============== ==========================================================
 
-.. _view-func-options:
 
 View Function Options
 ---------------------
@@ -770,19 +645,19 @@ customize behavior the view function would normally not have control over.
 The following attributes can be provided optionally to either override
 some defaults to :meth:`~flask.Flask.add_url_rule` or general behavior:
 
--   `__name__`: The name of a function is by default used as endpoint.  If
-    endpoint is provided explicitly this value is used.  Additionally this
+-   `__name__`: The name of a function is by default used as endpoint. If
+    endpoint is provided explicitly this value is used. Additionally this
     will be prefixed with the name of the blueprint by default which
     cannot be customized from the function itself.
 
 -   `methods`: If methods are not provided when the URL rule is added,
     Flask will look on the view function object itself if a `methods`
-    attribute exists.  If it does, it will pull the information for the
+    attribute exists. If it does, it will pull the information for the
     methods from there.
 
 -   `provide_automatic_options`: if this attribute is set Flask will
     either force enable or disable the automatic implementation of the
-    HTTP ``OPTIONS`` response.  This can be useful when working with
+    HTTP ``OPTIONS`` response. This can be useful when working with
     decorators that want to customize the ``OPTIONS`` response on a per-view
     basis.
 

docs/appcontext.rst

@@ -1,76 +1,63 @@
-.. currentmodule:: flask
+The App and Request Context
+===========================
 
-.. _app-context:
+The context keeps track of data and objects during a request, CLI command, or
+other activity. Rather than passing this data around to every function, the
+:data:`.current_app`, :data:`.g`, :data:`.request`, and :data:`.session` proxies
+are accessed instead.
 
-The Application Context
-=======================
+When handling a request, the context is referred to as the "request context"
+because it contains request data in addition to application data. Otherwise,
+such as during a CLI command, it is referred to as the "app context". During an
+app context, :data:`.current_app` and :data:`.g` are available, while during a
+request context :data:`.request` and :data:`.session` are also available.
 
-The application context keeps track of the application-level data during
-a request, CLI command, or other activity. Rather than passing the
-application around to each function, the :data:`current_app` and
-:data:`g` proxies are accessed instead.
-
-This is similar to the :doc:`/reqcontext`, which keeps track of
-request-level data during a request. A corresponding application context
-is pushed when a request context is pushed.
 
 Purpose of the Context
 ----------------------
 
-The :class:`Flask` application object has attributes, such as
-:attr:`~Flask.config`, that are useful to access within views and
-:doc:`CLI commands </cli>`. However, importing the ``app`` instance
-within the modules in your project is prone to circular import issues.
-When using the :doc:`app factory pattern </patterns/appfactories>` or
-writing reusable :doc:`blueprints </blueprints>` or
-:doc:`extensions </extensions>` there won't be an ``app`` instance to
-import at all.
+The context and proxies help solve two development issues: circular imports, and
+passing around global data during a request.
 
-Flask solves this issue with the *application context*. Rather than
-referring to an ``app`` directly, you use the the :data:`current_app`
-proxy, which points to the application handling the current activity.
+The :class:`.Flask` application object has attributes, such as
+:attr:`~.Flask.config`, that are useful to access within views and other
+functions. However, importing the ``app`` instance within the modules in your
+project is prone to circular import issues. When using the
+:doc:`app factory pattern </patterns/appfactories>` or writing reusable
+:doc:`blueprints </blueprints>` or :doc:`extensions </extensions>` there won't
+be an ``app`` instance to import at all.
 
-Flask automatically *pushes* an application context when handling a
-request. View functions, error handlers, and other functions that run
-during a request will have access to :data:`current_app`.
+When the application handles a request, it creates a :class:`.Request` object.
+Because a *worker* handles only one request at a time, the request data can be
+considered global to that worker during that request. Passing it as an argument
+through every function during the request becomes verbose and redundant.
 
-Flask will also automatically push an app context when running CLI
-commands registered with :attr:`Flask.cli` using ``@app.cli.command()``.
+Flask solves these issues with the *active context* pattern. Rather than
+importing an ``app`` directly, or having to pass it and the request through to
+every single function, you import and access the proxies, which point to the
+currently active application and request data. This is sometimes referred to
+as "context local" data.
 
 
-Lifetime of the Context
------------------------
+Context During Setup
+--------------------
 
-The application context is created and destroyed as necessary. When a
-Flask application begins handling a request, it pushes an application
-context and a :doc:`request context </reqcontext>`. When the request
-ends it pops the request context then the application context.
-Typically, an application context will have the same lifetime as a
-request.
-
-See :doc:`/reqcontext` for more information about how the contexts work
-and the full life cycle of a request.
-
-
-Manually Push a Context
------------------------
-
-If you try to access :data:`current_app`, or anything that uses it,
-outside an application context, you'll get this error message:
+If you try to access :data:`.current_app`, :data:`.g`, or anything that uses it,
+outside an app context, you'll get this error message:
 
 .. code-block:: pytb
 
     RuntimeError: Working outside of application context.
 
-    This typically means that you attempted to use functionality that
-    needed to interface with the current application object in some way.
-    To solve this, set up an application context with app.app_context().
+    Attempted to use functionality that expected a current application to be
+    set. To solve this, set up an app context using 'with app.app_context()'.
+    See the documentation on app context for more information.
 
 If you see that error while configuring your application, such as when
-initializing an extension, you can push a context manually since you
-have direct access to the ``app``. Use :meth:`~Flask.app_context` in a
-``with`` block, and everything that runs in the block will have access
-to :data:`current_app`. ::
+initializing an extension, you can push a context manually since you have direct
+access to the ``app``. Use :meth:`.Flask.app_context` in a ``with`` block.
+
+.. code-block:: python
 
     def create_app():
         app = Flask(__name__)
@@ -80,80 +67,121 @@ to :data:`current_app`. ::
 
         return app
 
-If you see that error somewhere else in your code not related to
-configuring the application, it most likely indicates that you should
-move that code into a view function or CLI command.
+If you see that error somewhere else in your code not related to setting up the
+application, it most likely indicates that you should move that code into a view
+function or CLI command.
 
 
-Storing Data
-------------
+Context During Testing
+----------------------
 
-The application context is a good place to store common data during a
-request or CLI command. Flask provides the :data:`g object <g>` for this
-purpose. It is a simple namespace object that has the same lifetime as
-an application context.
+See :doc:`/testing` for detailed information about managing the context during
+tests.
 
-.. note::
-    The ``g`` name stands for "global", but that is referring to the
-    data being global *within a context*. The data on ``g`` is lost
-    after the context ends, and it is not an appropriate place to store
-    data between requests. Use the :data:`session` or a database to
-    store data across requests.
+If you try to access :data:`.request`, :data:`.session`, or anything that uses
+it, outside a request context, you'll get this error message:
 
-A common use for :data:`g` is to manage resources during a request.
+.. code-block:: pytb
 
-1.  ``get_X()`` creates resource ``X`` if it does not exist, caching it
-    as ``g.X``.
-2.  ``teardown_X()`` closes or otherwise deallocates the resource if it
-    exists. It is registered as a :meth:`~Flask.teardown_appcontext`
-    handler.
+    RuntimeError: Working outside of request context.
 
-For example, you can manage a database connection using this pattern::
+    Attempted to use functionality that expected an active HTTP request. See the
+    documentation on request context for more information.
 
-    from flask import g
+This will probably only happen during tests. If you see that error somewhere
+else in your code not related to testing, it most likely indicates that you
+should move that code into a view function.
 
-    def get_db():
-        if 'db' not in g:
-            g.db = connect_to_database()
+The primary way to solve this is to use :meth:`.Flask.test_client` to simulate
+a full request.
 
-        return g.db
+If you only want to unit test one function, rather than a full request, use
+:meth:`.Flask.test_request_context` in a ``with`` block.
 
-    @app.teardown_appcontext
-    def teardown_db():
-        db = g.pop('db', None)
+.. code-block:: python
 
-        if db is not None:
-            db.close()
+    def generate_report(year):
+        format = request.args.get("format")
+        ...
 
-During a request, every call to ``get_db()`` will return the same
-connection, and it will be closed automatically at the end of the
-request.
-
-You can use :class:`~werkzeug.local.LocalProxy` to make a new context
-local from ``get_db()``::
-
-    from werkzeug.local import LocalProxy
-    db = LocalProxy(get_db)
-
-Accessing ``db`` will call ``get_db`` internally, in the same way that
-:data:`current_app` works.
-
-----
-
-If you're writing an extension, :data:`g` should be reserved for user
-code. You may store internal data on the context itself, but be sure to
-use a sufficiently unique name. The current context is accessed with
-:data:`_app_ctx_stack.top <_app_ctx_stack>`. For more information see
-:doc:`/extensiondev`.
+    with app.test_request_context(
+        "/make_report/2017", query_string={"format": "short"}
+    ):
+        generate_report()
 
 
-Events and Signals
-------------------
+.. _context-visibility:
 
-The application will call functions registered with
-:meth:`~Flask.teardown_appcontext` when the application context is
-popped.
+Visibility of the Context
+-------------------------
 
-If :data:`~signals.signals_available` is true, the following signals are
-sent: :data:`appcontext_pushed`, :data:`appcontext_tearing_down`, and
-:data:`appcontext_popped`.
+The context will have the same lifetime as an activity, such as a request, CLI
+command, or ``with`` block. Various callbacks and signals registered with the
+app will be run during the context.
+
+When a Flask application handles a request, it pushes a request context
+to set the active application and request data. When it handles a CLI command,
+it pushes an app context to set the active application. When the activity ends,
+it pops that context. Proxy objects like :data:`.request`, :data:`.session`,
+:data:`.g`, and :data:`.current_app`, are accessible while the context is pushed
+and active, and are not accessible after the context is popped.
+
+The context is unique to each thread (or other worker type). The proxies cannot
+be passed to another worker, which has a different context space and will not
+know about the active context in the parent's space.
+
+Besides being scoped to each worker, the proxy object has a separate type and
+identity than the proxied real object. In some cases you'll need access to the
+real object, rather than the proxy. Use the
+:meth:`~.LocalProxy._get_current_object` method in those cases.
+
+.. code-block:: python
+
+    app = current_app._get_current_object()
+    my_signal.send(app)
+
+
+Lifecycle of the Context
+------------------------
+
+Flask dispatches a request in multiple stages which can affect the request,
+response, and how errors are handled. See :doc:`/lifecycle` for a list of all
+the steps, callbacks, and signals during each request. The following are the
+steps directly related to the context.
+
+-   The app context is pushed, the proxies are available.
+-   The :data:`.appcontext_pushed` signal is sent.
+-   The request is dispatched.
+-   Any :meth:`.Flask.teardown_request` decorated functions are called.
+-   The :data:`.request_tearing_down` signal is sent.
+-   Any :meth:`.Flask.teardown_appcontext` decorated functions are called.
+-   The :data:`.appcontext_tearing_down` signal is sent.
+-   The app context is popped, the proxies are no longer available.
+-   The :data:`.appcontext_popped` signal is sent.
+
+The teardown callbacks are called by the context when it is popped. They are
+called even if there is an unhandled exception during dispatch. They may be
+called multiple times in some test scenarios. This means there is no guarantee
+that any other parts of the request dispatch have run. Be sure to write these
+functions in a way that does not depend on other callbacks. All callbacks are
+called even if any raise an error.
+
+
+How the Context Works
+---------------------
+
+Context locals are implemented using Python's :mod:`contextvars` and Werkzeug's
+:class:`~werkzeug.local.LocalProxy`. Python's contextvars are a low level
+structure to manage data local to a thread or coroutine. ``LocalProxy`` wraps
+the contextvar so that access to any attributes and methods is forwarded to the
+object stored in the contextvar.
+
+The context is tracked like a stack, with the active context at the top of the
+stack. Flask manages pushing and popping contexts during requests, CLI commands,
+testing, ``with`` blocks, etc. The proxies access attributes on the active
+context.
+
+Because it is a stack, other contexts may be pushed to change the proxies during
+an already active context. This is not a common pattern, but can be used in
+advanced use cases. For example, a Flask application can be used as WSGI
+middleware, calling another wrapped Flask app from a view.

docs/async-await.rst

@@ -0,0 +1,119 @@
+.. _async_await:
+
+Using ``async`` and ``await``
+=============================
+
+.. versionadded:: 2.0
+
+Routes, error handlers, before request, after request, and teardown
+functions can all be coroutine functions if Flask is installed with the
+``async`` extra (``pip install flask[async]``). This allows views to be
+defined with ``async def`` and use ``await``.
+
+.. code-block:: python
+
+    @app.route("/get-data")
+    async def get_data():
+        data = await async_db_query(...)
+        return jsonify(data)
+
+Pluggable class-based views also support handlers that are implemented as
+coroutines. This applies to the :meth:`~flask.views.View.dispatch_request`
+method in views that inherit from the :class:`flask.views.View` class, as
+well as all the HTTP method handlers in views that inherit from the
+:class:`flask.views.MethodView` class.
+
+
+Performance
+-----------
+
+Async functions require an event loop to run. Flask, as a WSGI
+application, uses one worker to handle one request/response cycle.
+When a request comes in to an async view, Flask will start an event loop
+in a thread, run the view function there, then return the result.
+
+Each request still ties up one worker, even for async views. The upside
+is that you can run async code within a view, for example to make
+multiple concurrent database queries, HTTP requests to an external API,
+etc. However, the number of requests your application can handle at one
+time will remain the same.
+
+**Async is not inherently faster than sync code.** Async is beneficial
+when performing concurrent IO-bound tasks, but will probably not improve
+CPU-bound tasks. Traditional Flask views will still be appropriate for
+most use cases, but Flask's async support enables writing and using
+code that wasn't possible natively before.
+
+
+Background tasks
+----------------
+
+Async functions will run in an event loop until they complete, at
+which stage the event loop will stop. This means any additional
+spawned tasks that haven't completed when the async function completes
+will be cancelled. Therefore you cannot spawn background tasks, for
+example via ``asyncio.create_task``.
+
+If you wish to use background tasks it is best to use a task queue to
+trigger background work, rather than spawn tasks in a view
+function. With that in mind you can spawn asyncio tasks by serving
+Flask with an ASGI server and utilising the asgiref WsgiToAsgi adapter
+as described in :doc:`deploying/asgi`. This works as the adapter creates
+an event loop that runs continually.
+
+
+When to use Quart instead
+-------------------------
+
+Flask's async support is less performant than async-first frameworks due
+to the way it is implemented. If you have a mainly async codebase it
+would make sense to consider `Quart`_. Quart is a reimplementation of
+Flask based on the `ASGI`_ standard instead of WSGI. This allows it to
+handle many concurrent requests, long running requests, and websockets
+without requiring multiple worker processes or threads.
+
+It has also already been possible to :doc:`run Flask with Gevent </gevent>` to
+get many of the benefits of async request handling. Gevent patches low-level
+Python functions to accomplish this, whereas ``async``/``await`` and ASGI use
+standard, modern Python capabilities. Deciding whether you should use gevent
+with Flask, or Quart, or something else is ultimately up to understanding the
+specific needs of your project.
+
+.. _Quart: https://quart.palletsprojects.com
+.. _ASGI: https://asgi.readthedocs.io
+
+
+Extensions
+----------
+
+Flask extensions predating Flask's async support do not expect async views.
+If they provide decorators to add functionality to views, those will probably
+not work with async views because they will not await the function or be
+awaitable. Other functions they provide will not be awaitable either and
+will probably be blocking if called within an async view.
+
+Extension authors can support async functions by utilising the
+:meth:`flask.Flask.ensure_sync` method. For example, if the extension
+provides a view function decorator add ``ensure_sync`` before calling
+the decorated function,
+
+.. code-block:: python
+
+    def extension(func):
+        @wraps(func)
+        def wrapper(*args, **kwargs):
+            ...  # Extension logic
+            return current_app.ensure_sync(func)(*args, **kwargs)
+
+        return wrapper
+
+Check the changelog of the extension you want to use to see if they've
+implemented async support, or make a feature request or PR to them.
+
+
+Other event loops
+-----------------
+
+At the moment Flask only supports :mod:`asyncio`. It's possible to override
+:meth:`flask.Flask.ensure_sync` to change how async functions are wrapped to use
+a different library. See :ref:`gevent-asyncio` for an example.

docs/becomingbig.rst

@@ -1,101 +0,0 @@
-.. _becomingbig:
-
-Becoming Big
-============
-
-Here are your options when growing your codebase or scaling your application.
-
-Read the Source.
-----------------
-
-Flask started in part to demonstrate how to build your own framework on top of
-existing well-used tools Werkzeug (WSGI) and Jinja (templating), and as it
-developed, it became useful to a wide audience.  As you grow your codebase,
-don't just use Flask -- understand it.  Read the source.  Flask's code is
-written to be read; its documentation is published so you can use its internal
-APIs.  Flask sticks to documented APIs in upstream libraries, and documents its
-internal utilities so that you can find the hook points needed for your
-project.
-
-Hook. Extend.
--------------
-
-The :ref:`api` docs are full of available overrides, hook points, and
-:ref:`signals`. You can provide custom classes for things like the
-request and response objects. Dig deeper on the APIs you use, and look
-for the customizations which are available out of the box in a Flask
-release. Look for ways in which your project can be refactored into a
-collection of utilities and Flask extensions. Explore the many
-:doc:`/extensions` in the community, and look for patterns to build your
-own extensions if you do not find the tools you need.
-
-Subclass.
----------
-
-The :class:`~flask.Flask` class has many methods designed for subclassing. You
-can quickly add or customize behavior by subclassing :class:`~flask.Flask` (see
-the linked method docs) and using that subclass wherever you instantiate an
-application class. This works well with :ref:`app-factories`. See :doc:`/patterns/subclassing` for an example.
-
-Wrap with middleware.
----------------------
-
-The :ref:`app-dispatch` chapter shows in detail how to apply middleware. You
-can introduce WSGI middleware to wrap your Flask instances and introduce fixes
-and changes at the layer between your Flask application and your HTTP
-server. Werkzeug includes several `middlewares
-<https://werkzeug.palletsprojects.com/middleware/>`_.
-
-Fork.
------
-
-If none of the above options work, fork Flask.  The majority of code of Flask
-is within Werkzeug and Jinja2.  These libraries do the majority of the work.
-Flask is just the paste that glues those together.  For every project there is
-the point where the underlying framework gets in the way (due to assumptions
-the original developers had).  This is natural because if this would not be the
-case, the framework would be a very complex system to begin with which causes a
-steep learning curve and a lot of user frustration.
-
-This is not unique to Flask.  Many people use patched and modified
-versions of their framework to counter shortcomings.  This idea is also
-reflected in the license of Flask.  You don't have to contribute any
-changes back if you decide to modify the framework.
-
-The downside of forking is of course that Flask extensions will most
-likely break because the new framework has a different import name.
-Furthermore integrating upstream changes can be a complex process,
-depending on the number of changes.  Because of that, forking should be
-the very last resort.
-
-Scale like a pro.
------------------
-
-For many web applications the complexity of the code is less an issue than
-the scaling for the number of users or data entries expected.  Flask by
-itself is only limited in terms of scaling by your application code, the
-data store you want to use and the Python implementation and webserver you
-are running on.
-
-Scaling well means for example that if you double the amount of servers
-you get about twice the performance.  Scaling bad means that if you add a
-new server the application won't perform any better or would not even
-support a second server.
-
-There is only one limiting factor regarding scaling in Flask which are
-the context local proxies.  They depend on context which in Flask is
-defined as being either a thread, process or greenlet.  If your server
-uses some kind of concurrency that is not based on threads or greenlets,
-Flask will no longer be able to support these global proxies.  However the
-majority of servers are using either threads, greenlets or separate
-processes to achieve concurrency which are all methods well supported by
-the underlying Werkzeug library.
-
-Discuss with the community.
----------------------------
-
-The Flask developers keep the framework accessible to users with codebases big
-and small. If you find an obstacle in your way, caused by Flask, don't hesitate
-to contact the developers on the mailing list or Discord server.  The best way for
-the Flask and Flask extension developers to improve the tools for larger
-applications is getting feedback from users.

docs/blueprints.rst

@@ -1,5 +1,3 @@
-.. _blueprints:
-
 Modular Applications with Blueprints
 ====================================
 
@@ -37,8 +35,9 @@ Blueprints in Flask are intended for these cases:
 A blueprint in Flask is not a pluggable app because it is not actually an
 application -- it's a set of operations which can be registered on an
 application, even multiple times.  Why not have multiple application
-objects?  You can do that (see :ref:`app-dispatch`), but your applications
-will have separate configs and will be managed at the WSGI layer.
+objects?  You can do that (see :doc:`/patterns/appdispatch`), but your
+applications will have separate configs and will be managed at the WSGI
+layer.
 
 Blueprints instead provide separation at the Flask level, share
 application config, and can change an application object as necessary with
@@ -70,7 +69,7 @@ implement a blueprint that does simple rendering of static templates::
     @simple_page.route('/<page>')
     def show(page):
         try:
-            return render_template('pages/%s.html' % page)
+            return render_template(f'pages/{page}.html')
         except TemplateNotFound:
             abort(404)
 
@@ -96,9 +95,10 @@ So how do you register that blueprint?  Like this::
 If you check the rules registered on the application, you will find
 these::
 
-    [<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>,
+    >>> app.url_map
+    Map([<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>,
      <Rule '/<page>' (HEAD, OPTIONS, GET) -> simple_page.show>,
-     <Rule '/' (HEAD, OPTIONS, GET) -> simple_page.show>]
+     <Rule '/' (HEAD, OPTIONS, GET) -> simple_page.show>])
 
 The first one is obviously from the application itself for the static
 files.  The other two are for the `show` function of the ``simple_page``
@@ -111,14 +111,53 @@ Blueprints however can also be mounted at different locations::
 
 And sure enough, these are the generated rules::
 
-    [<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>,
+    >>> app.url_map
+    Map([<Rule '/static/<filename>' (HEAD, OPTIONS, GET) -> static>,
      <Rule '/pages/<page>' (HEAD, OPTIONS, GET) -> simple_page.show>,
-     <Rule '/pages/' (HEAD, OPTIONS, GET) -> simple_page.show>]
+     <Rule '/pages/' (HEAD, OPTIONS, GET) -> simple_page.show>])
 
 On top of that you can register blueprints multiple times though not every
 blueprint might respond properly to that.  In fact it depends on how the
 blueprint is implemented if it can be mounted more than once.
 
+Nesting Blueprints
+------------------
+
+It is possible to register a blueprint on another blueprint.
+
+.. code-block:: python
+
+    parent = Blueprint('parent', __name__, url_prefix='/parent')
+    child = Blueprint('child', __name__, url_prefix='/child')
+    parent.register_blueprint(child)
+    app.register_blueprint(parent)
+
+The child blueprint will gain the parent's name as a prefix to its
+name, and child URLs will be prefixed with the parent's URL prefix.
+
+.. code-block:: python
+
+    url_for('parent.child.create')
+    /parent/child/create
+
+In addition a child blueprint's will gain their parent's subdomain,
+with their subdomain as prefix if present i.e.
+
+.. code-block:: python
+
+    parent = Blueprint('parent', __name__, subdomain='parent')
+    child = Blueprint('child', __name__, subdomain='child')
+    parent.register_blueprint(child)
+    app.register_blueprint(parent)
+
+    url_for('parent.child.create', _external=True)
+    "child.parent.domain.tld"
+
+Blueprint-specific before request functions, etc. registered with the
+parent will trigger for the child. If a child does not have an error
+handler that can handle a given exception, the parent's will be tried.
+
+
 Blueprint Resources
 -------------------
 
@@ -241,8 +280,9 @@ you can use relative redirects by prefixing the endpoint with a dot only::
 This will link to ``admin.index`` for instance in case the current request
 was dispatched to any other admin blueprint endpoint.
 
-Error Handlers
---------------
+
+Blueprint Error Handlers
+------------------------
 
 Blueprints support the ``errorhandler`` decorator just like the :class:`Flask`
 application object, so it is easy to make Blueprint-specific custom error
@@ -268,8 +308,8 @@ at the application level using the ``request`` proxy object::
     @app.errorhandler(405)
     def _handle_api_error(ex):
         if request.path.startswith('/api/'):
-            return jsonify_error(ex)
+            return jsonify(error=str(ex)), ex.code
         else:
             return ex
 
-More information on error handling see :ref:`errorpages`.
+See :doc:`/errorhandling`.

docs/changes.rst

@@ -1,4 +1,4 @@
-Changelog
-=========
+Changes
+=======
 
 .. include:: ../CHANGES.rst

docs/cli.rst

@@ -1,7 +1,5 @@
 .. currentmodule:: flask
 
-.. _cli:
-
 Command Line Interface
 ======================
 
@@ -17,58 +15,43 @@ Application Discovery
 ---------------------
 
 The ``flask`` command is installed by Flask, not your application; it must be
-told where to find your application in order to use it. The ``FLASK_APP``
-environment variable is used to specify how to load the application.
+told where to find your application in order to use it. The ``--app``
+option is used to specify how to load the application.
 
-Unix Bash (Linux, Mac, etc.)::
-
-    $ export FLASK_APP=hello
-    $ flask run
-
-Windows CMD::
-
-    > set FLASK_APP=hello
-    > flask run
-
-Windows PowerShell::
-
-    > $env:FLASK_APP = "hello"
-    > flask run
-
-While ``FLASK_APP`` supports a variety of options for specifying your
+While ``--app`` supports a variety of options for specifying your
 application, most use cases should be simple. Here are the typical values:
 
 (nothing)
-    The file :file:`wsgi.py` is imported, automatically detecting an app
-    (``app``). This provides an easy way to create an app from a factory with
-    extra arguments.
+    The name "app" or "wsgi" is imported (as a ".py" file, or package),
+    automatically detecting an app (``app`` or ``application``) or
+    factory (``create_app`` or ``make_app``).
 
-``FLASK_APP=hello``
-    The name is imported, automatically detecting an app (``app``) or factory
-    (``create_app``).
+``--app hello``
+    The given name is imported, automatically detecting an app (``app``
+    or ``application``) or factory (``create_app`` or ``make_app``).
 
 ----
 
-``FLASK_APP`` has three parts: an optional path that sets the current working
+``--app`` has three parts: an optional path that sets the current working
 directory, a Python file or dotted import path, and an optional variable
 name of the instance or factory. If the name is a factory, it can optionally
 be followed by arguments in parentheses. The following values demonstrate these
 parts:
 
-``FLASK_APP=src/hello``
+``--app src/hello``
     Sets the current working directory to ``src`` then imports ``hello``.
 
-``FLASK_APP=hello.web``
+``--app hello.web``
     Imports the path ``hello.web``.
 
-``FLASK_APP=hello:app2``
+``--app hello:app2``
     Uses the ``app2`` Flask instance in ``hello``.
 
-``FLASK_APP="hello:create_app('dev')"``
+``--app 'hello:create_app("dev")'``
     The ``create_app`` factory in ``hello`` is called with the string ``'dev'``
     as the argument.
 
-If ``FLASK_APP`` is not set, the command will try to import "app" or
+If ``--app`` is not set, the command will try to import "app" or
 "wsgi" (as a ".py" file, or package) and try to detect an application
 instance or factory.
 
@@ -77,11 +60,9 @@ Within the given import, the command looks for an application instance named
 found, the command looks for a factory function named ``create_app`` or
 ``make_app`` that returns an instance.
 
-When calling an application factory, if the factory takes an argument named
-``info``, then the :class:`~cli.ScriptInfo` instance is passed as a keyword
-argument. If parentheses follow the factory name, their contents are parsed
-as Python literals and passes as arguments to the function. This means that
-strings must still be in quotes.
+If parentheses follow the factory name, their contents are parsed as
+Python literals and passed as arguments and keyword arguments to the
+function. This means that strings must still be in quotes.
 
 
 Run the Development Server
@@ -90,14 +71,63 @@ Run the Development Server
 The :func:`run <cli.run_command>` command will start the development server. It
 replaces the :meth:`Flask.run` method in most cases. ::
 
-    $ flask run
+    $ flask --app hello run
      * Serving Flask app "hello"
      * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
 
 .. warning:: Do not use this command to run your application in production.
     Only use the development server during development. The development server
     is provided for convenience, but is not designed to be particularly secure,
-    stable, or efficient. See :ref:`deployment` for how to run in production.
+    stable, or efficient. See :doc:`/deploying/index` for how to run in production.
+
+If another program is already using port 5000, you'll see
+``OSError: [Errno 98]`` or ``OSError: [WinError 10013]`` when the
+server tries to start. See :ref:`address-already-in-use` for how to
+handle that.
+
+
+Debug Mode
+~~~~~~~~~~
+
+In debug mode, the ``flask run`` command will enable the interactive debugger and the
+reloader by default, and make errors easier to see and debug. To enable debug mode, use
+the ``--debug`` option.
+
+.. code-block:: console
+
+     $ flask --app hello run --debug
+      * Serving Flask app "hello"
+      * Debug mode: on
+      * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
+      * Restarting with inotify reloader
+      * Debugger is active!
+      * Debugger PIN: 223-456-919
+
+The ``--debug`` option can also be passed to the top level ``flask`` command to enable
+debug mode for any command. The following two ``run`` calls are equivalent.
+
+.. code-block:: console
+
+    $ flask --app hello --debug run
+    $ flask --app hello run --debug
+
+
+Watch and Ignore Files with the Reloader
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When using debug mode, the reloader will trigger whenever your Python code or imported
+modules change. The reloader can watch additional files with the ``--extra-files``
+option. Multiple paths are separated with ``:``, or ``;`` on Windows.
+
+.. code-block:: text
+
+    $ flask run --extra-files file1:dirA/file2:dirB/
+     * Running on http://127.0.0.1:8000/
+     * Detected change in '/path/to/file1', reloading
+
+The reloader can also ignore files using :mod:`fnmatch` patterns with the
+``--exclude-patterns`` option. Multiple patterns are separated with ``:``, or ``;`` on
+Windows.
 
 
 Open a Shell
@@ -108,63 +138,34 @@ shell with the :func:`shell <cli.shell_command>` command. An application
 context will be active, and the app instance will be imported. ::
 
     $ flask shell
-    Python 3.6.2 (default, Jul 20 2017, 03:52:27)
-    [GCC 7.1.1 20170630] on linux
-    App: example
-    Instance: /home/user/Projects/hello/instance
+    Python 3.10.0 (default, Oct 27 2021, 06:59:51) [GCC 11.1.0] on linux
+    App: example [production]
+    Instance: /home/david/Projects/pallets/flask/instance
     >>>
 
 Use :meth:`~Flask.shell_context_processor` to add other automatic imports.
 
 
-Environments
-------------
-
-.. versionadded:: 1.0
-
-The environment in which the Flask app runs is set by the
-:envvar:`FLASK_ENV` environment variable. If not set it defaults to
-``production``. The other recognized environment is ``development``.
-Flask and extensions may choose to enable behaviors based on the
-environment.
-
-If the env is set to ``development``, the ``flask`` command will enable
-debug mode and ``flask run`` will enable the interactive debugger and
-reloader.
-
-::
-
-    $ FLASK_ENV=development flask run
-     * Serving Flask app "hello"
-     * Environment: development
-     * Debug mode: on
-     * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)
-     * Restarting with inotify reloader
-     * Debugger is active!
-     * Debugger PIN: 223-456-919
-
-
-Debug Mode
-----------
-
-Debug mode will be enabled when :envvar:`FLASK_ENV` is ``development``,
-as described above. If you want to control debug mode separately, use
-:envvar:`FLASK_DEBUG`. The value ``1`` enables it, ``0`` disables it.
-
-
 .. _dotenv:
 
 Environment Variables From dotenv
 ---------------------------------
 
-Rather than setting ``FLASK_APP`` each time you open a new terminal, you can
-use Flask's dotenv support to set environment variables automatically.
+The ``flask`` command supports setting any option for any command with
+environment variables. The variables are named like ``FLASK_OPTION`` or
+``FLASK_COMMAND_OPTION``, for example ``FLASK_APP`` or
+``FLASK_RUN_PORT``.
+
+Rather than passing options every time you run a command, or environment
+variables every time you open a new terminal, you can use Flask's dotenv
+support to set environment variables automatically.
 
 If `python-dotenv`_ is installed, running the ``flask`` command will set
-environment variables defined in the files :file:`.env` and :file:`.flaskenv`.
-This can be used to avoid having to set ``FLASK_APP`` manually every time you
-open a new terminal, and to set configuration using environment variables
-similar to how some deployment services work.
+environment variables defined in the files ``.env`` and ``.flaskenv``.
+You can also specify an extra file to load with the ``--env-file``
+option. Dotenv files can be used to avoid having to set ``--app`` or
+``FLASK_APP`` manually, and to set configuration using environment
+variables similar to how some deployment services work.
 
 Variables set on the command line are used over those set in :file:`.env`,
 which are used over those set in :file:`.flaskenv`. :file:`.flaskenv` should be
@@ -172,9 +173,7 @@ used for public variables, such as ``FLASK_APP``, while :file:`.env` should not
 be committed to your repository so that it can set private variables.
 
 Directories are scanned upwards from the directory you call ``flask``
-from to locate the files. The current working directory will be set to the
-location of the file, with the assumption that that is the top level project
-directory.
+from to locate the files.
 
 The files are only loaded by the ``flask`` command or calling
 :meth:`~Flask.run`. If you would like to load these files when running in
@@ -191,11 +190,39 @@ environment variables. The variables use the pattern
 ``FLASK_COMMAND_OPTION``. For example, to set the port for the run
 command, instead of ``flask run --port 8000``:
 
-.. code-block:: bash
+.. tabs::
 
-    $ export FLASK_RUN_PORT=8000
-    $ flask run
-     * Running on http://127.0.0.1:8000/
+   .. group-tab:: Bash
+
+      .. code-block:: text
+
+         $ export FLASK_RUN_PORT=8000
+         $ flask run
+          * Running on http://127.0.0.1:8000/
+
+   .. group-tab:: Fish
+
+      .. code-block:: text
+
+         $ set -x FLASK_RUN_PORT 8000
+         $ flask run
+          * Running on http://127.0.0.1:8000/
+
+   .. group-tab:: CMD
+
+      .. code-block:: text
+
+         > set FLASK_RUN_PORT=8000
+         > flask run
+          * Running on http://127.0.0.1:8000/
+
+   .. group-tab:: Powershell
+
+      .. code-block:: text
+
+         > $env:FLASK_RUN_PORT = 8000
+         > flask run
+          * Running on http://127.0.0.1:8000/
 
 These can be added to the ``.flaskenv`` file just like ``FLASK_APP`` to
 control default command options.
@@ -219,10 +246,35 @@ a project runner that loads them already. Keep in mind that the
 environment variables must be set before the app loads or it won't
 configure as expected.
 
-.. code-block:: bash
+.. tabs::
 
-    $ export FLASK_SKIP_DOTENV=1
-    $ flask run
+   .. group-tab:: Bash
+
+      .. code-block:: text
+
+         $ export FLASK_SKIP_DOTENV=1
+         $ flask run
+
+   .. group-tab:: Fish
+
+      .. code-block:: text
+
+         $ set -x FLASK_SKIP_DOTENV 1
+         $ flask run
+
+   .. group-tab:: CMD
+
+      .. code-block:: text
+
+         > set FLASK_SKIP_DOTENV=1
+         > flask run
+
+   .. group-tab:: Powershell
+
+      .. code-block:: text
+
+         > $env:FLASK_SKIP_DOTENV = 1
+         > flask run
 
 
 Environment Variables From virtualenv
@@ -232,13 +284,31 @@ If you do not want to install dotenv support, you can still set environment
 variables by adding them to the end of the virtualenv's :file:`activate`
 script. Activating the virtualenv will set the variables.
 
-Unix Bash, :file:`venv/bin/activate`::
+.. tabs::
 
-    $ export FLASK_APP=hello
+   .. group-tab:: Bash
 
-Windows CMD, :file:`venv\\Scripts\\activate.bat`::
+      Unix Bash, :file:`.venv/bin/activate`::
 
-    > set FLASK_APP=hello
+          $ export FLASK_APP=hello
+
+   .. group-tab:: Fish
+
+      Fish, :file:`.venv/bin/activate.fish`::
+
+          $ set -x FLASK_APP hello
+
+   .. group-tab:: CMD
+
+      Windows CMD, :file:`.venv\\Scripts\\activate.bat`::
+
+          > set FLASK_APP=hello
+
+   .. group-tab:: Powershell
+
+      Windows Powershell, :file:`.venv\\Scripts\\activate.ps1`::
+
+          > $env:FLASK_APP = "hello"
 
 It is preferred to use dotenv support over this, since :file:`.flaskenv` can be
 committed to the repository so that it works automatically wherever the project
@@ -293,15 +363,72 @@ See :ref:`testing-cli` for an overview of how to test your custom
 commands.
 
 
+Registering Commands with Blueprints
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If your application uses blueprints, you can optionally register CLI
+commands directly onto them. When your blueprint is registered onto your
+application, the associated commands will be available to the ``flask``
+command. By default, those commands will be nested in a group matching
+the name of the blueprint.
+
+.. code-block:: python
+
+    from flask import Blueprint
+
+    bp = Blueprint('students', __name__)
+
+    @bp.cli.command('create')
+    @click.argument('name')
+    def create(name):
+        ...
+
+    app.register_blueprint(bp)
+
+.. code-block:: text
+
+    $ flask students create alice
+
+You can alter the group name by specifying the ``cli_group`` parameter
+when creating the :class:`Blueprint` object, or later with
+:meth:`app.register_blueprint(bp, cli_group='...') <Flask.register_blueprint>`.
+The following are equivalent:
+
+.. code-block:: python
+
+    bp = Blueprint('students', __name__, cli_group='other')
+    # or
+    app.register_blueprint(bp, cli_group='other')
+
+.. code-block:: text
+
+    $ flask other create alice
+
+Specifying ``cli_group=None`` will remove the nesting and merge the
+commands directly to the application's level:
+
+.. code-block:: python
+
+    bp = Blueprint('students', __name__, cli_group=None)
+    # or
+    app.register_blueprint(bp, cli_group=None)
+
+.. code-block:: text
+
+    $ flask create alice
+
+
 Application Context
 ~~~~~~~~~~~~~~~~~~~
 
-Commands added using the Flask app's :attr:`~Flask.cli`
-:meth:`~cli.AppGroup.command` decorator will be executed with an application
-context pushed, so your command and extensions have access to the app and its
-configuration. If you create a command using the Click :func:`~click.command`
-decorator instead of the Flask decorator, you can use
-:func:`~cli.with_appcontext` to get the same behavior. ::
+Commands added using the Flask app's :attr:`~Flask.cli` or
+:class:`~flask.cli.FlaskGroup` :meth:`~cli.AppGroup.command` decorator
+will be executed with an application context pushed, so your custom
+commands and parameters have access to the app and its configuration. The
+:func:`~cli.with_appcontext` decorator can be used to get the same
+behavior, but is not needed in most cases.
+
+.. code-block:: python
 
     import click
     from flask.cli import with_appcontext
@@ -313,36 +440,22 @@ decorator instead of the Flask decorator, you can use
 
     app.cli.add_command(do_work)
 
-If you're sure a command doesn't need the context, you can disable it::
-
-    @app.cli.command(with_appcontext=False)
-    def do_work():
-        ...
-
 
 Plugins
 -------
 
 Flask will automatically load commands specified in the ``flask.commands``
 `entry point`_. This is useful for extensions that want to add commands when
-they are installed. Entry points are specified in :file:`setup.py` ::
+they are installed. Entry points are specified in :file:`pyproject.toml`:
 
-    from setuptools import setup
-
-    setup(
-        name='flask-my-extension',
-        ...,
-        entry_points={
-            'flask.commands': [
-                'my-command=flask_my_extension.commands:cli'
-            ],
-        },
-    )
+.. code-block:: toml
 
+    [project.entry-points."flask.commands"]
+    my-command = "my_extension.commands:cli"
 
 .. _entry point: https://packaging.python.org/tutorials/packaging-projects/#entry-points
 
-Inside :file:`flask_my_extension/commands.py` you can then export a Click
+Inside :file:`my_extension/commands.py` you can then export a Click
 object::
 
     import click
@@ -361,7 +474,7 @@ Custom Scripts
 --------------
 
 When you are using the app factory pattern, it may be more convenient to define
-your own Click script. Instead of using ``FLASK_APP`` and letting Flask load
+your own Click script. Instead of using ``--app`` and letting Flask load
 your application, you can create your own Click object and export it as a
 `console script`_ entry point.
 
@@ -380,22 +493,15 @@ Create an instance of :class:`~cli.FlaskGroup` and pass it the factory::
     def cli():
         """Management script for the Wiki application."""
 
-Define the entry point in :file:`setup.py`::
+Define the entry point in :file:`pyproject.toml`:
 
-    from setuptools import setup
+.. code-block:: toml
 
-    setup(
-        name='flask-my-extension',
-        ...,
-        entry_points={
-            'console_scripts': [
-                'wiki=wiki:cli'
-            ],
-        },
-    )
+    [project.scripts]
+    wiki = "wiki:cli"
 
 Install the application in the virtualenv in editable mode and the custom
-script is available. Note that you don't need to set ``FLASK_APP``. ::
+script is available. Note that you don't need to set ``--app``. ::
 
     $ pip install -e .
     $ wiki run
@@ -415,52 +521,36 @@ script is available. Note that you don't need to set ``FLASK_APP``. ::
 PyCharm Integration
 -------------------
 
-Prior to PyCharm 2018.1, the Flask CLI features weren't yet fully
-integrated into PyCharm. We have to do a few tweaks to get them working
-smoothly. These instructions should be similar for any other IDE you
-might want to use.
+PyCharm Professional provides a special Flask run configuration to run the development
+server. For the Community Edition, and for other commands besides ``run``, you need to
+create a custom run configuration. These instructions should be similar for any other
+IDE you use.
 
-In PyCharm, with your project open, click on *Run* from the menu bar and
-go to *Edit Configurations*. You'll be greeted by a screen similar to
-this:
+In PyCharm, with your project open, click on *Run* from the menu bar and go to *Edit
+Configurations*. You'll see a screen similar to this:
 
-.. image:: _static/pycharm-runconfig.png
+.. image:: _static/pycharm-run-config.png
     :align: center
     :class: screenshot
-    :alt: screenshot of pycharm's run configuration settings
+    :alt: Screenshot of PyCharm run configuration.
 
-There's quite a few options to change, but once we've done it for one
-command, we can easily copy the entire configuration and make a single
-tweak to give us access to other commands, including any custom ones you
-may implement yourself.
+Once you create a configuration for the ``flask run``, you can copy and change it to
+call any other command.
 
-Click the + (*Add New Configuration*) button and select *Python*. Give
-the configuration a good descriptive name such as "Run Flask Server".
-For the ``flask run`` command, check "Single instance only" since you
-can't run the server more than once at the same time.
+Click the *+ (Add New Configuration)* button and select *Python*. Give the configuration
+a name such as "flask run".
 
-Select *Module name* from the dropdown (**A**) then input ``flask``.
+Click the *Script path* dropdown and change it to *Module name*, then input ``flask``.
 
-The *Parameters* field (**B**) is set to the CLI command to execute
-(with any arguments). In this example we use ``run``, which will run
-the development server.
+The *Parameters* field is set to the CLI command to execute along with any arguments.
+This example uses ``--app hello run --debug``, which will run the development server in
+debug mode. ``--app hello`` should be the import or file with your Flask app.
 
-You can skip this next step if you're using :ref:`dotenv`. We need to
-add an environment variable (**C**) to identify our application. Click
-on the browse button and add an entry with ``FLASK_APP`` on the left and
-the Python import or file on the right (``hello`` for example).
+If you installed your project as a package in your virtualenv, you may uncheck the
+*PYTHONPATH* options. This will more accurately match how you deploy later.
 
-Next we need to set the working directory (**D**) to be the folder where
-our application resides.
+Click *OK* to save and close the configuration. Select the configuration in the main
+PyCharm window and click the play button next to it to run the server.
 
-If you have installed your project as a package in your virtualenv, you
-may untick the *PYTHONPATH* options (**E**). This will more accurately
-match how you deploy the app later.
-
-Click *Apply* to save the configuration, or *OK* to save and close the
-window. Select the configuration in the main PyCharm window and click
-the play button next to it to run the server.
-
-Now that we have a configuration which runs ``flask run`` from within
-PyCharm, we can copy that configuration and alter the *Script* argument
-to run a different CLI command, e.g. ``flask shell``.
+Now that you have a configuration for ``flask run``, you can copy that configuration and
+change the *Parameters* argument to run a different CLI command.

docs/conf.py

@@ -11,25 +11,33 @@ release, version = get_version("Flask")
 
 # General --------------------------------------------------------------
 
-master_doc = "index"
+default_role = "code"
 extensions = [
     "sphinx.ext.autodoc",
+    "sphinx.ext.extlinks",
     "sphinx.ext.intersphinx",
     "sphinxcontrib.log_cabinet",
+    "sphinx_tabs.tabs",
     "pallets_sphinx_themes",
-    "sphinx_issues",
 ]
+autodoc_member_order = "bysource"
+autodoc_typehints = "description"
+autodoc_preserve_defaults = True
+extlinks = {
+    "issue": ("https://github.com/pallets/flask/issues/%s", "#%s"),
+    "pr": ("https://github.com/pallets/flask/pull/%s", "#%s"),
+    "ghsa": ("https://github.com/pallets/flask/security/advisories/GHSA-%s", "GHSA-%s"),
+}
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3/", None),
     "werkzeug": ("https://werkzeug.palletsprojects.com/", None),
     "click": ("https://click.palletsprojects.com/", None),
-    "jinja": ("http://jinja.pocoo.org/docs/", None),
+    "jinja": ("https://jinja.palletsprojects.com/", None),
     "itsdangerous": ("https://itsdangerous.palletsprojects.com/", None),
     "sqlalchemy": ("https://docs.sqlalchemy.org/", None),
-    "wtforms": ("https://wtforms.readthedocs.io/en/stable/", None),
-    "blinker": ("https://pythonhosted.org/blinker/", None),
+    "wtforms": ("https://wtforms.readthedocs.io/", None),
+    "blinker": ("https://blinker.readthedocs.io/", None),
 }
-issues_github_path = "pallets/flask"
 
 # HTML -----------------------------------------------------------------
 
@@ -37,29 +45,26 @@ html_theme = "flask"
 html_theme_options = {"index_sidebar_logo": False}
 html_context = {
     "project_links": [
-        ProjectLink("Donate to Pallets", "https://palletsprojects.com/donate"),
-        ProjectLink("Flask Website", "https://palletsprojects.com/p/flask/"),
-        ProjectLink("PyPI releases", "https://pypi.org/project/Flask/"),
+        ProjectLink("Donate", "https://palletsprojects.com/donate"),
+        ProjectLink("PyPI Releases", "https://pypi.org/project/Flask/"),
         ProjectLink("Source Code", "https://github.com/pallets/flask/"),
         ProjectLink("Issue Tracker", "https://github.com/pallets/flask/issues/"),
+        ProjectLink("Chat", "https://discord.gg/pallets"),
     ]
 }
 html_sidebars = {
-    "index": ["project.html", "localtoc.html", "searchbox.html"],
-    "**": ["localtoc.html", "relations.html", "searchbox.html"],
+    "index": ["project.html", "localtoc.html", "searchbox.html", "ethicalads.html"],
+    "**": ["localtoc.html", "relations.html", "searchbox.html", "ethicalads.html"],
 }
-singlehtml_sidebars = {"index": ["project.html", "localtoc.html"]}
+singlehtml_sidebars = {"index": ["project.html", "localtoc.html", "ethicalads.html"]}
 html_static_path = ["_static"]
-html_favicon = "_static/flask-icon.png"
-html_logo = "_static/flask-icon.png"
-html_title = "Flask Documentation ({})".format(version)
+html_favicon = "_static/flask-icon.svg"
+html_logo = "_static/flask-logo.svg"
+html_title = f"Flask Documentation ({version})"
 html_show_sourcelink = False
 
-# LaTeX ----------------------------------------------------------------
-
-latex_documents = [
-    (master_doc, "Flask-{}.tex".format(version), html_title, author, "manual")
-]
+gettext_uuid = True
+gettext_compact = False
 
 # Local Extensions -----------------------------------------------------
 
@@ -76,9 +81,9 @@ def github_link(name, rawtext, text, lineno, inliner, options=None, content=None
         words = None
 
     if packaging.version.parse(release).is_devrelease:
-        url = "{0}master/{1}".format(base_url, text)
+        url = f"{base_url}main/{text}"
     else:
-        url = "{0}{1}/{2}".format(base_url, release, text)
+        url = f"{base_url}{release}/{text}"
 
     if words is None:
         words = url

docs/config.rst

@@ -1,5 +1,3 @@
-.. _config:
-
 Configuration Handling
 ======================
 
@@ -40,45 +38,26 @@ method::
 
     app.config.update(
         TESTING=True,
-        SECRET_KEY=b'_5#y2L"F4Q8z\n\xec]/'
+        SECRET_KEY='192b9bdd22ab9ed4d12e236c78afcb9a393ec15f71bbf5dc987d54727823bcbf'
     )
 
 
-Environment and Debug Features
-------------------------------
+Debug Mode
+----------
 
-The :data:`ENV` and :data:`DEBUG` config values are special because they
-may behave inconsistently if changed after the app has begun setting up.
-In order to set the environment and debug mode reliably, Flask uses
-environment variables.
+The :data:`DEBUG` config value is special because it may behave inconsistently if
+changed after the app has begun setting up. In order to set debug mode reliably, use the
+``--debug`` option on the ``flask`` or ``flask run`` command. ``flask run`` will use the
+interactive debugger and reloader by default in debug mode.
 
-The environment is used to indicate to Flask, extensions, and other
-programs, like Sentry, what context Flask is running in. It is
-controlled with the :envvar:`FLASK_ENV` environment variable and
-defaults to ``production``.
+.. code-block:: text
 
-Setting :envvar:`FLASK_ENV` to ``development`` will enable debug mode.
-``flask run`` will use the interactive debugger and reloader by default
-in debug mode. To control this separately from the environment, use the
-:envvar:`FLASK_DEBUG` flag.
+    $ flask --app hello run --debug
 
-.. versionchanged:: 1.0
-    Added :envvar:`FLASK_ENV` to control the environment separately
-    from debug mode. The development environment enables debug mode.
-
-To switch Flask to the development environment and enable debug mode,
-set :envvar:`FLASK_ENV`::
-
-    $ export FLASK_ENV=development
-    $ flask run
-
-(On Windows, use ``set`` instead of ``export``.)
-
-Using the environment variables as described above is recommended. While
-it is possible to set :data:`ENV` and :data:`DEBUG` in your config or
-code, this is strongly discouraged. They can't be read early by the
-``flask`` command, and some systems or extensions may have already
-configured themselves based on a previous value.
+Using the option is recommended. While it is possible to set :data:`DEBUG` in your
+config or code, this is strongly discouraged. It can't be read early by the
+``flask run`` command, and some systems or extensions may have already configured
+themselves based on a previous value.
 
 
 Builtin Configuration Values
@@ -86,38 +65,21 @@ Builtin Configuration Values
 
 The following configuration values are used internally by Flask:
 
-.. py:data:: ENV
-
-    What environment the app is running in. Flask and extensions may
-    enable behaviors based on the environment, such as enabling debug
-    mode. The :attr:`~flask.Flask.env` attribute maps to this config
-    key. This is set by the :envvar:`FLASK_ENV` environment variable and
-    may not behave as expected if set in code.
-
-    **Do not enable development when deploying in production.**
-
-    Default: ``'production'``
-
-    .. versionadded:: 1.0
-
 .. py:data:: DEBUG
 
-    Whether debug mode is enabled. When using ``flask run`` to start the
-    development server, an interactive debugger will be shown for
-    unhandled exceptions, and the server will be reloaded when code
-    changes. The :attr:`~flask.Flask.debug` attribute maps to this
-    config key. This is enabled when :data:`ENV` is ``'development'``
-    and is overridden by the ``FLASK_DEBUG`` environment variable. It
-    may not behave as expected if set in code.
+    Whether debug mode is enabled. When using ``flask run`` to start the development
+    server, an interactive debugger will be shown for unhandled exceptions, and the
+    server will be reloaded when code changes. The :attr:`~flask.Flask.debug` attribute
+    maps to this config key. This is set with the ``FLASK_DEBUG`` environment variable.
+    It may not behave as expected if set in code.
 
     **Do not enable debug mode when deploying in production.**
 
-    Default: ``True`` if :data:`ENV` is ``'development'``, or ``False``
-    otherwise.
+    Default: ``False``
 
 .. py:data:: TESTING
 
-    Enable testing mode. Exceptions are propagated rather than handled by the
+    Enable testing mode. Exceptions are propagated rather than handled by
     the app's error handlers. Extensions may also change their behavior to
     facilitate easier testing. You should enable this in your own tests.
 
@@ -131,14 +93,6 @@ The following configuration values are used internally by Flask:
 
     Default: ``None``
 
-.. py:data:: PRESERVE_CONTEXT_ON_EXCEPTION
-
-    Don't pop the request context when an exception occurs. If not set, this
-    is true if ``DEBUG`` is true. This allows debuggers to introspect the
-    request data on errors, and should normally not need to be set directly.
-
-    Default: ``None``
-
 .. py:data:: TRAP_HTTP_EXCEPTIONS
 
     If there is no handler for an ``HTTPException``-type exception, re-raise it
@@ -161,16 +115,35 @@ The following configuration values are used internally by Flask:
 
     A secret key that will be used for securely signing the session cookie
     and can be used for any other security related needs by extensions or your
-    application. It should be a long random string of bytes, although unicode
-    is accepted too. For example, copy the output of this to your config::
+    application. It should be a long random ``bytes`` or ``str``. For
+    example, copy the output of this to your config::
 
-        python -c 'import os; print(os.urandom(16))'
-        b'_5#y2L"F4Q8z\n\xec]/'
+        $ python -c 'import secrets; print(secrets.token_hex())'
+        '192b9bdd22ab9ed4d12e236c78afcb9a393ec15f71bbf5dc987d54727823bcbf'
 
     **Do not reveal the secret key when posting questions or committing code.**
 
     Default: ``None``
 
+.. py:data:: SECRET_KEY_FALLBACKS
+
+    A list of old secret keys that can still be used for unsigning. This allows
+    a project to implement key rotation without invalidating active sessions or
+    other recently-signed secrets.
+
+    Keys should be removed after an appropriate period of time, as checking each
+    additional key adds some overhead.
+
+    Order should not matter, but the default implementation will test the last
+    key in the list first, so it might make sense to order oldest to newest.
+
+    Flask's built-in secure cookie session supports this. Extensions that use
+    :data:`SECRET_KEY` may not support this yet.
+
+    Default: ``None``
+
+    .. versionadded:: 3.1
+
 .. py:data:: SESSION_COOKIE_NAME
 
     The name of the session cookie. Can be changed in case you already have a
@@ -180,12 +153,23 @@ The following configuration values are used internally by Flask:
 
 .. py:data:: SESSION_COOKIE_DOMAIN
 
-    The domain match rule that the session cookie will be valid for. If not
-    set, the cookie will be valid for all subdomains of :data:`SERVER_NAME`.
-    If ``False``, the cookie's domain will not be set.
+    The value of the ``Domain`` parameter on the session cookie. If not set, browsers
+    will only send the cookie to the exact domain it was set from. Otherwise, they
+    will send it to any subdomain of the given value as well.
+
+    Not setting this value is more restricted and secure than setting it.
 
     Default: ``None``
 
+    .. warning::
+        If this is changed after the browser created a cookie is created with
+        one setting, it may result in another being created. Browsers may send
+        send both in an undefined order. In that case, you may want to change
+        :data:`SESSION_COOKIE_NAME` as well or otherwise invalidate old sessions.
+
+    .. versionchanged:: 2.3
+        Not set by default, does not fall back to ``SERVER_NAME``.
+
 .. py:data:: SESSION_COOKIE_PATH
 
     The path that the session cookie will be valid for. If not set, the cookie
@@ -208,6 +192,23 @@ The following configuration values are used internally by Flask:
 
     Default: ``False``
 
+.. py:data:: SESSION_COOKIE_PARTITIONED
+
+    Browsers will send cookies based on the top-level document's domain, rather
+    than only the domain of the document setting the cookie. This prevents third
+    party cookies set in iframes from "leaking" between separate sites.
+
+    Browsers are beginning to disallow non-partitioned third party cookies, so
+    you need to mark your cookies partitioned if you expect them to work in such
+    embedded situations.
+
+    Enabling this implicitly enables :data:`SESSION_COOKIE_SECURE` as well, as
+    it is only valid when served over HTTPS.
+
+    Default: ``False``
+
+    .. versionadded:: 3.1
+
 .. py:data:: SESSION_COOKIE_SAMESITE
 
     Restrict how cookies are sent with requests from external sites. Can
@@ -249,34 +250,61 @@ The following configuration values are used internally by Flask:
 .. py:data:: SEND_FILE_MAX_AGE_DEFAULT
 
     When serving files, set the cache control max age to this number of
-    seconds.  Can either be a :class:`datetime.timedelta` or an ``int``.
+    seconds. Can be a :class:`datetime.timedelta` or an ``int``.
     Override this value on a per-file basis using
-    :meth:`~flask.Flask.get_send_file_max_age` on the application or blueprint.
+    :meth:`~flask.Flask.get_send_file_max_age` on the application or
+    blueprint.
 
-    Default: ``timedelta(hours=12)`` (``43200`` seconds)
+    If ``None``, ``send_file`` tells the browser to use conditional
+    requests will be used instead of a timed cache, which is usually
+    preferable.
+
+    Default: ``None``
+
+.. py:data:: TRUSTED_HOSTS
+
+    Validate :attr:`.Request.host` and other attributes that use it against
+    these trusted values. Raise a :exc:`~werkzeug.exceptions.SecurityError` if
+    the host is invalid, which results in a 400 error. If it is ``None``, all
+    hosts are valid. Each value is either an exact match, or can start with
+    a dot ``.`` to match any subdomain.
+
+    Validation is done during routing against this value. ``before_request`` and
+    ``after_request`` callbacks will still be called.
+
+    Default: ``None``
+
+    .. versionadded:: 3.1
 
 .. py:data:: SERVER_NAME
 
-    Inform the application what host and port it is bound to. Required
-    for subdomain route matching support.
+    Inform the application what host and port it is bound to.
 
-    If set, will be used for the session cookie domain if
-    :data:`SESSION_COOKIE_DOMAIN` is not set. Modern web browsers will
-    not allow setting cookies for domains without a dot. To use a domain
-    locally, add any names that should route to the app to your
-    ``hosts`` file. ::
+    Must be set if ``subdomain_matching`` is enabled, to be able to extract the
+    subdomain from the request.
 
-        127.0.0.1 localhost.dev
-
-    If set, ``url_for`` can generate external URLs with only an application
-    context instead of a request context.
+    Must be set for ``url_for`` to generate external URLs outside of a
+    request context.
 
     Default: ``None``
 
+    .. versionchanged:: 3.1
+        Does not restrict requests to only this domain, for both
+        ``subdomain_matching`` and ``host_matching``.
+
+    .. versionchanged:: 1.0
+        Does not implicitly enable ``subdomain_matching``.
+
+    .. versionchanged:: 2.3
+        Does not affect ``SESSION_COOKIE_DOMAIN``.
+
 .. py:data:: APPLICATION_ROOT
 
     Inform the application what path it is mounted under by the application /
-    web server.
+    web server.  This is used for generating URLs outside the context of a
+    request (inside a request, the dispatcher is responsible for setting
+    ``SCRIPT_NAME`` instead; see :doc:`/patterns/appdispatch`
+    for examples of dispatch configuration).
 
     Will be used for the session cookie path if ``SESSION_COOKIE_PATH`` is not
     set.
@@ -291,42 +319,53 @@ The following configuration values are used internally by Flask:
 
 .. py:data:: MAX_CONTENT_LENGTH
 
-    Don't read more than this many bytes from the incoming request data. If not
-    set and the request does not specify a ``CONTENT_LENGTH``, no data will be
-    read for security.
+    The maximum number of bytes that will be read during this request. If
+    this limit is exceeded, a 413 :exc:`~werkzeug.exceptions.RequestEntityTooLarge`
+    error is raised. If it is set to ``None``, no limit is enforced at the
+    Flask application level. However, if it is ``None`` and the request has no
+    ``Content-Length`` header and the WSGI server does not indicate that it
+    terminates the stream, then no data is read to avoid an infinite stream.
+
+    Each request defaults to this config. It can be set on a specific
+    :attr:`.Request.max_content_length` to apply the limit to that specific
+    view. This should be set appropriately based on an application's or view's
+    specific needs.
 
     Default: ``None``
 
-.. py:data:: JSON_AS_ASCII
+    .. versionadded:: 0.6
 
-    Serialize objects to ASCII-encoded JSON. If this is disabled, the JSON
-    will be returned as a Unicode string, or encoded as ``UTF-8`` by
-    ``jsonify``. This has security implications when rendering the JSON into
-    JavaScript in templates, and should typically remain enabled.
+.. py:data:: MAX_FORM_MEMORY_SIZE
 
-    Default: ``True``
+    The maximum size in bytes any non-file form field may be in a
+    ``multipart/form-data`` body. If this limit is exceeded, a 413
+    :exc:`~werkzeug.exceptions.RequestEntityTooLarge` error is raised. If it is
+    set to ``None``, no limit is enforced at the Flask application level.
 
-.. py:data:: JSON_SORT_KEYS
+    Each request defaults to this config. It can be set on a specific
+    :attr:`.Request.max_form_memory_parts` to apply the limit to that specific
+    view. This should be set appropriately based on an application's or view's
+    specific needs.
 
-    Sort the keys of JSON objects alphabetically. This is useful for caching
-    because it ensures the data is serialized the same way no matter what
-    Python's hash seed is. While not recommended, you can disable this for a
-    possible performance improvement at the cost of caching.
+    Default: ``500_000``
 
-    Default: ``True``
+    .. versionadded:: 3.1
 
-.. py:data:: JSONIFY_PRETTYPRINT_REGULAR
+.. py:data:: MAX_FORM_PARTS
 
-    ``jsonify`` responses will be output with newlines, spaces, and indentation
-    for easier reading by humans. Always enabled in debug mode.
+    The maximum number of fields that may be present in a
+    ``multipart/form-data`` body. If this limit is exceeded, a 413
+    :exc:`~werkzeug.exceptions.RequestEntityTooLarge` error is raised. If it
+    is set to ``None``, no limit is enforced at the Flask application level.
 
-    Default: ``False``
+    Each request defaults to this config. It can be set on a specific
+    :attr:`.Request.max_form_parts` to apply the limit to that specific view.
+    This should be set appropriately based on an application's or view's
+    specific needs.
 
-.. py:data:: JSONIFY_MIMETYPE
+    Default: ``1_000``
 
-    The mimetype of ``jsonify`` responses.
-
-    Default: ``'application/json'``
+    .. versionadded:: 3.1
 
 .. py:data:: TEMPLATES_AUTO_RELOAD
 
@@ -349,6 +388,12 @@ The following configuration values are used internally by Flask:
     ``4093``. Larger cookies may be silently ignored by browsers. Set to
     ``0`` to disable the warning.
 
+.. py:data:: PROVIDE_AUTOMATIC_OPTIONS
+
+    Set to ``False`` to disable the automatic addition of OPTIONS
+    responses. This can be overridden per route by altering the
+    ``provide_automatic_options`` attribute.
+
 .. versionadded:: 0.4
    ``LOGGER_NAME``
 
@@ -379,7 +424,7 @@ The following configuration values are used internally by Flask:
 
 .. versionchanged:: 1.0
     ``LOGGER_NAME`` and ``LOGGER_HANDLER_POLICY`` were removed. See
-    :ref:`logging` for information about configuration.
+    :doc:`/logging` for information about configuration.
 
     Added :data:`ENV` to reflect the :envvar:`FLASK_ENV` environment
     variable.
@@ -389,17 +434,30 @@ The following configuration values are used internally by Flask:
 
     Added :data:`MAX_COOKIE_SIZE` to control a warning from Werkzeug.
 
+.. versionchanged:: 2.2
+    Removed ``PRESERVE_CONTEXT_ON_EXCEPTION``.
 
-Configuring from Files
-----------------------
+.. versionchanged:: 2.3
+    ``JSON_AS_ASCII``, ``JSON_SORT_KEYS``, ``JSONIFY_MIMETYPE``, and
+    ``JSONIFY_PRETTYPRINT_REGULAR`` were removed. The default ``app.json`` provider has
+    equivalent attributes instead.
 
-Configuration becomes more useful if you can store it in a separate file,
-ideally located outside the actual application package. This makes
-packaging and distributing your application possible via various package
-handling tools (:ref:`distribute-deployment`) and finally modifying the
-configuration file afterwards.
+.. versionchanged:: 2.3
+    ``ENV`` was removed.
 
-So a common pattern is this::
+.. versionadded:: 3.1
+    Added :data:`PROVIDE_AUTOMATIC_OPTIONS` to control the default
+    addition of autogenerated OPTIONS responses.
+
+
+Configuring from Python Files
+-----------------------------
+
+Configuration becomes more useful if you can store it in a separate file, ideally
+located outside the actual application package. You can deploy your application, then
+separately configure it for the specific deployment.
+
+A common pattern is this::
 
     app = Flask(__name__)
     app.config.from_object('yourapplication.default_settings')
@@ -408,18 +466,42 @@ So a common pattern is this::
 This first loads the configuration from the
 `yourapplication.default_settings` module and then overrides the values
 with the contents of the file the :envvar:`YOURAPPLICATION_SETTINGS`
-environment variable points to.  This environment variable can be set on
-Linux or OS X with the export command in the shell before starting the
-server::
+environment variable points to.  This environment variable can be set
+in the shell before starting the server:
 
-    $ export YOURAPPLICATION_SETTINGS=/path/to/settings.cfg
-    $ python run-app.py
-     * Running on http://127.0.0.1:5000/
-     * Restarting with reloader...
+.. tabs::
 
-On Windows systems use the `set` builtin instead::
+   .. group-tab:: Bash
 
-    >set YOURAPPLICATION_SETTINGS=\path\to\settings.cfg
+      .. code-block:: text
+
+         $ export YOURAPPLICATION_SETTINGS=/path/to/settings.cfg
+         $ flask run
+          * Running on http://127.0.0.1:5000/
+
+   .. group-tab:: Fish
+
+      .. code-block:: text
+
+         $ set -x YOURAPPLICATION_SETTINGS /path/to/settings.cfg
+         $ flask run
+          * Running on http://127.0.0.1:5000/
+
+   .. group-tab:: CMD
+
+      .. code-block:: text
+
+         > set YOURAPPLICATION_SETTINGS=\path\to\settings.cfg
+         > flask run
+          * Running on http://127.0.0.1:5000/
+
+   .. group-tab:: Powershell
+
+      .. code-block:: text
+
+         > $env:YOURAPPLICATION_SETTINGS = "\path\to\settings.cfg"
+         > flask run
+          * Running on http://127.0.0.1:5000/
 
 The configuration files themselves are actual Python files.  Only values
 in uppercase are actually stored in the config object later on.  So make
@@ -428,8 +510,7 @@ sure to use uppercase letters for your config keys.
 Here is an example of a configuration file::
 
     # Example configuration
-    DEBUG = False
-    SECRET_KEY = b'_5#y2L"F4Q8z\n\xec]/'
+    SECRET_KEY = '192b9bdd22ab9ed4d12e236c78afcb9a393ec15f71bbf5dc987d54727823bcbf'
 
 Make sure to load the configuration very early on, so that extensions have
 the ability to access the configuration when starting up.  There are other
@@ -438,50 +519,116 @@ complete reference, read the :class:`~flask.Config` object's
 documentation.
 
 
+Configuring from Data Files
+---------------------------
+
+It is also possible to load configuration from a file in a format of
+your choice using :meth:`~flask.Config.from_file`. For example to load
+from a TOML file:
+
+.. code-block:: python
+
+    import tomllib
+    app.config.from_file("config.toml", load=tomllib.load, text=False)
+
+Or from a JSON file:
+
+.. code-block:: python
+
+    import json
+    app.config.from_file("config.json", load=json.load)
+
+
 Configuring from Environment Variables
 --------------------------------------
 
-In addition to pointing to configuration files using environment variables, you
-may find it useful (or necessary) to control your configuration values directly
-from the environment.
+In addition to pointing to configuration files using environment
+variables, you may find it useful (or necessary) to control your
+configuration values directly from the environment. Flask can be
+instructed to load all environment variables starting with a specific
+prefix into the config using :meth:`~flask.Config.from_prefixed_env`.
 
-Environment variables can be set on Linux or OS X with the export command in
-the shell before starting the server::
+Environment variables can be set in the shell before starting the
+server:
 
-    $ export SECRET_KEY='5f352379324c22463451387a0aec5d2f'
-    $ export MAIL_ENABLED=false
-    $ python run-app.py
-     * Running on http://127.0.0.1:5000/
+.. tabs::
 
-On Windows systems use the ``set`` builtin instead::
+   .. group-tab:: Bash
 
-    >set SECRET_KEY='5f352379324c22463451387a0aec5d2f'
+      .. code-block:: text
 
-While this approach is straightforward to use, it is important to remember that
-environment variables are strings -- they are not automatically deserialized
-into Python types.
+         $ export FLASK_SECRET_KEY="5f352379324c22463451387a0aec5d2f"
+         $ export FLASK_MAIL_ENABLED=false
+         $ flask run
+          * Running on http://127.0.0.1:5000/
 
-Here is an example of a configuration file that uses environment variables::
+   .. group-tab:: Fish
 
-    import os
+      .. code-block:: text
 
-    _mail_enabled = os.environ.get("MAIL_ENABLED", default="true")
-    MAIL_ENABLED = _mail_enabled.lower() in {"1", "t", "true"}
+         $ set -x FLASK_SECRET_KEY "5f352379324c22463451387a0aec5d2f"
+         $ set -x FLASK_MAIL_ENABLED false
+         $ flask run
+          * Running on http://127.0.0.1:5000/
 
-    SECRET_KEY = os.environ.get("SECRET_KEY")
+   .. group-tab:: CMD
 
-    if not SECRET_KEY:
-        raise ValueError("No SECRET_KEY set for Flask application")
+      .. code-block:: text
 
+         > set FLASK_SECRET_KEY="5f352379324c22463451387a0aec5d2f"
+         > set FLASK_MAIL_ENABLED=false
+         > flask run
+          * Running on http://127.0.0.1:5000/
 
-Notice that any value besides an empty string will be interpreted as a boolean
-``True`` value in Python, which requires care if an environment explicitly sets
-values intended to be ``False``.
+   .. group-tab:: Powershell
 
-Make sure to load the configuration very early on, so that extensions have the
-ability to access the configuration when starting up.  There are other methods
-on the config object as well to load from individual files.  For a complete
-reference, read the :class:`~flask.Config` class documentation.
+      .. code-block:: text
+
+         > $env:FLASK_SECRET_KEY = "5f352379324c22463451387a0aec5d2f"
+         > $env:FLASK_MAIL_ENABLED = "false"
+         > flask run
+          * Running on http://127.0.0.1:5000/
+
+The variables can then be loaded and accessed via the config with a key
+equal to the environment variable name without the prefix i.e.
+
+.. code-block:: python
+
+    app.config.from_prefixed_env()
+    app.config["SECRET_KEY"]  # Is "5f352379324c22463451387a0aec5d2f"
+
+The prefix is ``FLASK_`` by default. This is configurable via the
+``prefix`` argument of :meth:`~flask.Config.from_prefixed_env`.
+
+Values will be parsed to attempt to convert them to a more specific type
+than strings. By default :func:`json.loads` is used, so any valid JSON
+value is possible, including lists and dicts. This is configurable via
+the ``loads`` argument of :meth:`~flask.Config.from_prefixed_env`.
+
+When adding a boolean value with the default JSON parsing, only "true"
+and "false", lowercase, are valid values. Keep in mind that any
+non-empty string is considered ``True`` by Python.
+
+It is possible to set keys in nested dictionaries by separating the
+keys with double underscore (``__``). Any intermediate keys that don't
+exist on the parent dict will be initialized to an empty dict.
+
+.. code-block:: text
+
+    $ export FLASK_MYAPI__credentials__username=user123
+
+.. code-block:: python
+
+    app.config["MYAPI"]["credentials"]["username"]  # Is "user123"
+
+On Windows, environment variable keys are always uppercase, therefore
+the above example would end up as ``MYAPI__CREDENTIALS__USERNAME``.
+
+For even more config loading features, including merging and
+case-insensitive Windows support, try a dedicated library such as
+Dynaconf_, which includes integration with Flask.
+
+.. _Dynaconf: https://www.dynaconf.com/
 
 
 Configuration Best Practices
@@ -501,6 +648,10 @@ that experience:
     limit yourself to request-only accesses to the configuration you can
     reconfigure the object later on as needed.
 
+3.  Make sure to load the configuration very early on, so that
+    extensions can access the configuration when calling ``init_app``.
+
+
 .. _config-dev-prod:
 
 Development / Production
@@ -533,17 +684,16 @@ An interesting pattern is also to use classes and inheritance for
 configuration::
 
     class Config(object):
-        DEBUG = False
         TESTING = False
-        DATABASE_URI = 'sqlite:///:memory:'
 
     class ProductionConfig(Config):
         DATABASE_URI = 'mysql://user@localhost/foo'
 
     class DevelopmentConfig(Config):
-        DEBUG = True
+        DATABASE_URI = "sqlite:////tmp/foo.db"
 
     class TestingConfig(Config):
+        DATABASE_URI = 'sqlite:///:memory:'
         TESTING = True
 
 To enable such a config you just have to call into
@@ -563,18 +713,17 @@ then you must do so before calling :meth:`~flask.Config.from_object`::
     cfg = import_string('configmodule.ProductionConfig')()
     app.config.from_object(cfg)
 
-Instantiating the configutation object allows you to use ``@property`` in
+Instantiating the configuration object allows you to use ``@property`` in
 your configuration classes::
 
     class Config(object):
         """Base config, uses staging database server."""
-        DEBUG = False
         TESTING = False
         DB_SERVER = '192.168.1.56'
 
         @property
-        def DATABASE_URI(self):         # Note: all caps
-            return 'mysql://user@{}/foo'.format(self.DB_SERVER)
+        def DATABASE_URI(self):  # Note: all caps
+            return f"mysql://user@{self.DB_SERVER}/foo"
 
     class ProductionConfig(Config):
         """Uses production database server."""
@@ -582,11 +731,9 @@ your configuration classes::
 
     class DevelopmentConfig(Config):
         DB_SERVER = 'localhost'
-        DEBUG = True
 
     class TestingConfig(Config):
         DB_SERVER = 'localhost'
-        DEBUG = True
         DATABASE_URI = 'sqlite:///:memory:'
 
 There are many different ways and it's up to you how you want to manage
@@ -602,12 +749,10 @@ your configuration files.  However here a list of good recommendations:
     code at all.  If you are working often on different projects you can
     even create your own script for sourcing that activates a virtualenv
     and exports the development configuration for you.
--   Use a tool like `fabric`_ in production to push code and
-    configurations separately to the production server(s).  For some
-    details about how to do that, head over to the
-    :ref:`fabric-deployment` pattern.
+-   Use a tool like `fabric`_ to push code and configuration separately
+    to the production server(s).
 
-.. _fabric: http://www.fabfile.org/
+.. _fabric: https://www.fabfile.org/
 
 
 .. _instance-folders:
@@ -655,7 +800,7 @@ locations are used:
 
 -   Installed module or package::
 
-        $PREFIX/lib/python2.X/site-packages/myapp
+        $PREFIX/lib/pythonX.Y/site-packages/myapp
         $PREFIX/var/myapp-instance
 
     ``$PREFIX`` is the prefix of your Python installation.  This can be

docs/contributing.rst

@@ -1 +1,8 @@
-.. include:: ../CONTRIBUTING.rst
+Contributing
+============
+
+See the Pallets `detailed contributing documentation <contrib_>`_ for many ways
+to contribute, including reporting issues, requesting features, asking or
+answering questions, and making PRs.
+
+.. _contrib: https://palletsprojects.com/contributing/

docs/debugging.rst

@@ -0,0 +1,99 @@
+Debugging Application Errors
+============================
+
+
+In Production
+-------------
+
+**Do not run the development server, or enable the built-in debugger, in
+a production environment.** The debugger allows executing arbitrary
+Python code from the browser. It's protected by a pin, but that should
+not be relied on for security.
+
+Use an error logging tool, such as Sentry, as described in
+:ref:`error-logging-tools`, or enable logging and notifications as
+described in :doc:`/logging`.
+
+If you have access to the server, you could add some code to start an
+external debugger if ``request.remote_addr`` matches your IP. Some IDE
+debuggers also have a remote mode so breakpoints on the server can be
+interacted with locally. Only enable a debugger temporarily.
+
+
+The Built-In Debugger
+---------------------
+
+The built-in Werkzeug development server provides a debugger which shows
+an interactive traceback in the browser when an unhandled error occurs
+during a request. This debugger should only be used during development.
+
+.. image:: _static/debugger.png
+   :align: center
+   :class: screenshot
+   :alt: screenshot of debugger in action
+
+.. warning::
+
+    The debugger allows executing arbitrary Python code from the
+    browser. It is protected by a pin, but still represents a major
+    security risk. Do not run the development server or debugger in a
+    production environment.
+
+The debugger is enabled by default when the development server is run in debug mode.
+
+.. code-block:: text
+
+    $ flask --app hello run --debug
+
+When running from Python code, passing ``debug=True`` enables debug mode, which is
+mostly equivalent.
+
+.. code-block:: python
+
+    app.run(debug=True)
+
+:doc:`/server` and :doc:`/cli` have more information about running the debugger and
+debug mode. More information about the debugger can be found in the `Werkzeug
+documentation <https://werkzeug.palletsprojects.com/debug/>`__.
+
+
+External Debuggers
+------------------
+
+External debuggers, such as those provided by IDEs, can offer a more
+powerful debugging experience than the built-in debugger. They can also
+be used to step through code during a request before an error is raised,
+or if no error is raised. Some even have a remote mode so you can debug
+code running on another machine.
+
+When using an external debugger, the app should still be in debug mode, otherwise Flask
+turns unhandled errors into generic 500 error pages. However, the built-in debugger and
+reloader should be disabled so they don't interfere with the external debugger.
+
+.. code-block:: text
+
+    $ flask --app hello run --debug --no-debugger --no-reload
+
+When running from Python:
+
+.. code-block:: python
+
+    app.run(debug=True, use_debugger=False, use_reloader=False)
+
+Disabling these isn't required, an external debugger will continue to work with the
+following caveats.
+
+-   If the built-in debugger is not disabled, it will catch unhandled exceptions before
+    the external debugger can.
+-   If the reloader is not disabled, it could cause an unexpected reload if code changes
+    during a breakpoint.
+-   The development server will still catch unhandled exceptions if the built-in
+    debugger is disabled, otherwise it would crash on any error. If you want that (and
+    usually you don't) pass ``passthrough_errors=True`` to ``app.run``.
+
+    .. code-block:: python
+
+        app.run(
+            debug=True, passthrough_errors=True,
+            use_debugger=False, use_reloader=False
+        )

docs/deploying/apache-httpd.rst

@@ -0,0 +1,66 @@
+Apache httpd
+============
+
+`Apache httpd`_ is a fast, production level HTTP server. When serving
+your application with one of the WSGI servers listed in :doc:`index`, it
+is often good or necessary to put a dedicated HTTP server in front of
+it. This "reverse proxy" can handle incoming requests, TLS, and other
+security and performance concerns better than the WSGI server.
+
+httpd can be installed using your system package manager, or a pre-built
+executable for Windows. Installing and running httpd itself is outside
+the scope of this doc. This page outlines the basics of configuring
+httpd to proxy your application. Be sure to read its documentation to
+understand what features are available.
+
+.. _Apache httpd: https://httpd.apache.org/
+
+
+Domain Name
+-----------
+
+Acquiring and configuring a domain name is outside the scope of this
+doc. In general, you will buy a domain name from a registrar, pay for
+server space with a hosting provider, and then point your registrar
+at the hosting provider's name servers.
+
+To simulate this, you can also edit your ``hosts`` file, located at
+``/etc/hosts`` on Linux. Add a line that associates a name with the
+local IP.
+
+Modern Linux systems may be configured to treat any domain name that
+ends with ``.localhost`` like this without adding it to the ``hosts``
+file.
+
+.. code-block:: python
+    :caption: ``/etc/hosts``
+
+    127.0.0.1 hello.localhost
+
+
+Configuration
+-------------
+
+The httpd configuration is located at ``/etc/httpd/conf/httpd.conf`` on
+Linux. It may be different depending on your operating system. Check the
+docs and look for ``httpd.conf``.
+
+Remove or comment out any existing ``DocumentRoot`` directive. Add the
+config lines below. We'll assume the WSGI server is listening locally at
+``http://127.0.0.1:8000``.
+
+.. code-block:: apache
+    :caption: ``/etc/httpd/conf/httpd.conf``
+
+    LoadModule proxy_module modules/mod_proxy.so
+    LoadModule proxy_http_module modules/mod_proxy_http.so
+    ProxyPass / http://127.0.0.1:8000/
+    RequestHeader set X-Forwarded-Proto http
+    RequestHeader set X-Forwarded-Prefix /
+
+The ``LoadModule`` lines might already exist. If so, make sure they are
+uncommented instead of adding them manually.
+
+Then :doc:`proxy_fix` so that your application uses the ``X-Forwarded``
+headers. ``X-Forwarded-For`` and ``X-Forwarded-Host`` are automatically
+set by ``ProxyPass``.

docs/deploying/asgi.rst

@@ -0,0 +1,27 @@
+ASGI
+====
+
+If you'd like to use an ASGI server you will need to utilise WSGI to
+ASGI middleware. The asgiref
+`WsgiToAsgi <https://github.com/django/asgiref#wsgi-to-asgi-adapter>`_
+adapter is recommended as it integrates with the event loop used for
+Flask's :ref:`async_await` support. You can use the adapter by
+wrapping the Flask app,
+
+.. code-block:: python
+
+    from asgiref.wsgi import WsgiToAsgi
+    from flask import Flask
+
+    app = Flask(__name__)
+
+    ...
+
+    asgi_app = WsgiToAsgi(app)
+
+and then serving the ``asgi_app`` with the ASGI server, e.g. using
+`Hypercorn <https://github.com/pgjones/hypercorn>`_,
+
+.. sourcecode:: text
+
+    $ hypercorn module:asgi_app

docs/deploying/cgi.rst

@@ -1,61 +0,0 @@
-CGI
-===
-
-If all other deployment methods do not work, CGI will work for sure.
-CGI is supported by all major servers but usually has a sub-optimal
-performance.
-
-This is also the way you can use a Flask application on Google's `App
-Engine`_, where execution happens in a CGI-like environment.
-
-.. admonition:: Watch Out
-
-   Please make sure in advance that any ``app.run()`` calls you might
-   have in your application file are inside an ``if __name__ ==
-   '__main__':`` block or moved to a separate file.  Just make sure it's
-   not called because this will always start a local WSGI server which
-   we do not want if we deploy that application to CGI / app engine.
-
-   With CGI, you will also have to make sure that your code does not contain
-   any ``print`` statements, or that ``sys.stdout`` is overridden by something
-   that doesn't write into the HTTP response.
-
-Creating a `.cgi` file
-----------------------
-
-First you need to create the CGI application file.  Let's call it
-:file:`yourapplication.cgi`::
-
-    #!/usr/bin/python
-    from wsgiref.handlers import CGIHandler
-    from yourapplication import app
-
-    CGIHandler().run(app)
-
-Server Setup
-------------
-
-Usually there are two ways to configure the server.  Either just copy the
-``.cgi`` into a :file:`cgi-bin` (and use `mod_rewrite` or something similar to
-rewrite the URL) or let the server point to the file directly.
-
-In Apache for example you can put something like this into the config:
-
-.. sourcecode:: apache
-
-    ScriptAlias /app /path/to/the/application.cgi
-
-On shared webhosting, though, you might not have access to your Apache config.
-In this case, a file called ``.htaccess``, sitting in the public directory you want
-your app to be available, works too but the ``ScriptAlias`` directive won't
-work in that case:
-
-.. sourcecode:: apache
-
-    RewriteEngine On
-    RewriteCond %{REQUEST_FILENAME} !-f # Don't interfere with static files
-    RewriteRule ^(.*)$ /path/to/the/application.cgi/$1 [L]
-
-For more information consult the documentation of your webserver.
-
-.. _App Engine: https://cloud.google.com/appengine/docs/

docs/deploying/eventlet.rst

@@ -0,0 +1,8 @@
+:orphan:
+
+eventlet
+========
+
+`Eventlet is no longer maintained.`__ Use :doc:`/deploying/gevent` instead.
+
+__ https://eventlet.readthedocs.io

docs/deploying/fastcgi.rst

@@ -1,240 +0,0 @@
-.. _deploying-fastcgi:
-
-FastCGI
-=======
-
-FastCGI is a deployment option on servers like `nginx`_, `lighttpd`_, and
-`cherokee`_; see :ref:`deploying-uwsgi` and :ref:`deploying-wsgi-standalone`
-for other options.  To use your WSGI application with any of them you will need
-a FastCGI server first.  The most popular one is `flup`_ which we will use for
-this guide.  Make sure to have it installed to follow along.
-
-.. admonition:: Watch Out
-
-   Please make sure in advance that any ``app.run()`` calls you might
-   have in your application file are inside an ``if __name__ ==
-   '__main__':`` block or moved to a separate file.  Just make sure it's
-   not called because this will always start a local WSGI server which
-   we do not want if we deploy that application to FastCGI.
-
-Creating a `.fcgi` file
------------------------
-
-First you need to create the FastCGI server file.  Let's call it
-`yourapplication.fcgi`::
-
-    #!/usr/bin/python
-    from flup.server.fcgi import WSGIServer
-    from yourapplication import app
-
-    if __name__ == '__main__':
-        WSGIServer(app).run()
-
-This is enough for Apache to work, however nginx and older versions of
-lighttpd need a socket to be explicitly passed to communicate with the
-FastCGI server.  For that to work you need to pass the path to the
-socket to the :class:`~flup.server.fcgi.WSGIServer`::
-
-    WSGIServer(application, bindAddress='/path/to/fcgi.sock').run()
-
-The path has to be the exact same path you define in the server
-config.
-
-Save the :file:`yourapplication.fcgi` file somewhere you will find it again.
-It makes sense to have that in :file:`/var/www/yourapplication` or something
-similar.
-
-Make sure to set the executable bit on that file so that the servers
-can execute it:
-
-.. sourcecode:: text
-
-    # chmod +x /var/www/yourapplication/yourapplication.fcgi
-
-Configuring Apache
-------------------
-
-The example above is good enough for a basic Apache deployment but your
-`.fcgi` file will appear in your application URL e.g.
-``example.com/yourapplication.fcgi/news/``. There are few ways to configure
-your application so that yourapplication.fcgi does not appear in the URL.
-A preferable way is to use the ScriptAlias and SetHandler configuration
-directives to route requests to the FastCGI server. The following example
-uses FastCgiServer to start 5 instances of the application which will
-handle all incoming requests::
-
-    LoadModule fastcgi_module /usr/lib64/httpd/modules/mod_fastcgi.so
-
-    FastCgiServer /var/www/html/yourapplication/app.fcgi -idle-timeout 300 -processes 5
-
-    <VirtualHost *>
-        ServerName webapp1.mydomain.com
-        DocumentRoot /var/www/html/yourapplication
-
-        AddHandler fastcgi-script fcgi
-        ScriptAlias / /var/www/html/yourapplication/app.fcgi/
-
-        <Location />
-            SetHandler fastcgi-script
-        </Location>
-    </VirtualHost>
-
-These processes will be managed by Apache. If you're using a standalone
-FastCGI server, you can use the FastCgiExternalServer directive instead.
-Note that in the following the path is not real, it's simply used as an
-identifier to other
-directives such as AliasMatch::
-
-    FastCgiServer /var/www/html/yourapplication -host 127.0.0.1:3000
-
-If you cannot set ScriptAlias, for example on a shared web host, you can use
-WSGI middleware to remove yourapplication.fcgi from the URLs. Set .htaccess::
-
-    <IfModule mod_fcgid.c>
-       AddHandler fcgid-script .fcgi
-       <Files ~ (\.fcgi)>
-           SetHandler fcgid-script
-           Options +FollowSymLinks +ExecCGI
-       </Files>
-    </IfModule>
-
-    <IfModule mod_rewrite.c>
-       Options +FollowSymlinks
-       RewriteEngine On
-       RewriteBase /
-       RewriteCond %{REQUEST_FILENAME} !-f
-       RewriteRule ^(.*)$ yourapplication.fcgi/$1 [QSA,L]
-    </IfModule>
-
-Set yourapplication.fcgi::
-
-    #!/usr/bin/python
-    #: optional path to your local python site-packages folder
-    import sys
-    sys.path.insert(0, '<your_local_path>/lib/python<your_python_version>/site-packages')
-
-    from flup.server.fcgi import WSGIServer
-    from yourapplication import app
-
-    class ScriptNameStripper(object):
-       def __init__(self, app):
-           self.app = app
-
-       def __call__(self, environ, start_response):
-           environ['SCRIPT_NAME'] = ''
-           return self.app(environ, start_response)
-
-    app = ScriptNameStripper(app)
-
-    if __name__ == '__main__':
-        WSGIServer(app).run()
-
-Configuring lighttpd
---------------------
-
-A basic FastCGI configuration for lighttpd looks like that::
-
-    fastcgi.server = ("/yourapplication.fcgi" =>
-        ((
-            "socket" => "/tmp/yourapplication-fcgi.sock",
-            "bin-path" => "/var/www/yourapplication/yourapplication.fcgi",
-            "check-local" => "disable",
-            "max-procs" => 1
-        ))
-    )
-
-    alias.url = (
-        "/static/" => "/path/to/your/static/"
-    )
-
-    url.rewrite-once = (
-        "^(/static($|/.*))$" => "$1",
-        "^(/.*)$" => "/yourapplication.fcgi$1"
-    )
-
-Remember to enable the FastCGI, alias and rewrite modules. This configuration
-binds the application to ``/yourapplication``.  If you want the application to
-work in the URL root you have to work around a lighttpd bug with the
-:class:`~werkzeug.contrib.fixers.LighttpdCGIRootFix` middleware.
-
-Make sure to apply it only if you are mounting the application the URL
-root. Also, see the Lighty docs for more information on `FastCGI and Python
-<https://redmine.lighttpd.net/projects/lighttpd/wiki/Docs_ModFastCGI>`_ (note that
-explicitly passing a socket to run() is no longer necessary).
-
-Configuring nginx
------------------
-
-Installing FastCGI applications on nginx is a bit different because by
-default no FastCGI parameters are forwarded.
-
-A basic Flask FastCGI configuration for nginx looks like this::
-
-    location = /yourapplication { rewrite ^ /yourapplication/ last; }
-    location /yourapplication { try_files $uri @yourapplication; }
-    location @yourapplication {
-        include fastcgi_params;
-        fastcgi_split_path_info ^(/yourapplication)(.*)$;
-        fastcgi_param PATH_INFO $fastcgi_path_info;
-        fastcgi_param SCRIPT_NAME $fastcgi_script_name;
-        fastcgi_pass unix:/tmp/yourapplication-fcgi.sock;
-    }
-
-This configuration binds the application to ``/yourapplication``.  If you
-want to have it in the URL root it's a bit simpler because you don't
-have to figure out how to calculate ``PATH_INFO`` and ``SCRIPT_NAME``::
-
-    location / { try_files $uri @yourapplication; }
-    location @yourapplication {
-        include fastcgi_params;
-        fastcgi_param PATH_INFO $fastcgi_script_name;
-        fastcgi_param SCRIPT_NAME "";
-        fastcgi_pass unix:/tmp/yourapplication-fcgi.sock;
-    }
-
-Running FastCGI Processes
--------------------------
-
-Since nginx and others do not load FastCGI apps, you have to do it by
-yourself.  `Supervisor can manage FastCGI processes.
-<http://supervisord.org/configuration.html#fcgi-program-x-section-settings>`_
-You can look around for other FastCGI process managers or write a script
-to run your `.fcgi` file at boot, e.g. using a SysV ``init.d`` script.
-For a temporary solution, you can always run the ``.fcgi`` script inside
-GNU screen.  See ``man screen`` for details, and note that this is a
-manual solution which does not persist across system restart::
-
-    $ screen
-    $ /var/www/yourapplication/yourapplication.fcgi
-
-Debugging
----------
-
-FastCGI deployments tend to be hard to debug on most web servers.  Very
-often the only thing the server log tells you is something along the
-lines of "premature end of headers".  In order to debug the application
-the only thing that can really give you ideas why it breaks is switching
-to the correct user and executing the application by hand.
-
-This example assumes your application is called `application.fcgi` and
-that your web server user is `www-data`::
-
-    $ su www-data
-    $ cd /var/www/yourapplication
-    $ python application.fcgi
-    Traceback (most recent call last):
-      File "yourapplication.fcgi", line 4, in <module>
-    ImportError: No module named yourapplication
-
-In this case the error seems to be "yourapplication" not being on the
-python path.  Common problems are:
-
--   Relative paths being used.  Don't rely on the current working directory.
--   The code depending on environment variables that are not set by the
-    web server.
--   Different python interpreters being used.
-
-.. _nginx: https://nginx.org/
-.. _lighttpd: https://www.lighttpd.net/
-.. _cherokee: http://cherokee-project.com/
-.. _flup: https://pypi.org/project/flup/

docs/deploying/gevent.rst

@@ -0,0 +1,76 @@
+gevent
+======
+
+Prefer using :doc:`gunicorn` or :doc:`uwsgi` with gevent workers rather
+than using `gevent`_ directly. Gunicorn and uWSGI provide much more
+configurable and production-tested servers.
+
+`gevent`_ allows writing asynchronous, coroutine-based code that looks
+like standard synchronous Python. It uses `greenlet`_ to enable task
+switching without writing ``async/await`` or using ``asyncio``. This is
+not the same as Python's ``async/await``, or the ASGI server spec.
+
+gevent provides a WSGI server that can handle many connections at once
+instead of one per worker process. See :doc:`/gevent` for more
+information about enabling it in your application.
+
+.. _gevent: https://www.gevent.org/
+.. _greenlet: https://greenlet.readthedocs.io/en/latest/
+
+
+Installing
+----------
+
+When using gevent, greenlet>=1.0 is required. When using PyPy,
+PyPy>=7.3.7 is required.
+
+Create a virtualenv, install your application, then install ``gevent``.
+
+.. code-block:: text
+
+    $ cd hello-app
+    $ python -m venv .venv
+    $ . .venv/bin/activate
+    $ pip install .  # install your application
+    $ pip install gevent
+
+
+Running
+-------
+
+To use gevent to serve your application, write a script that imports its
+``WSGIServer``, as well as your app or app factory.
+
+.. code-block:: python
+    :caption: ``wsgi.py``
+
+    from gevent.pywsgi import WSGIServer
+    from hello import create_app
+
+    app = create_app()
+    http_server = WSGIServer(("127.0.0.1", 8000), app)
+    http_server.serve_forever()
+
+.. code-block:: text
+
+    $ python wsgi.py
+
+No output is shown when the server starts.
+
+
+Binding Externally
+------------------
+
+gevent should not be run as root because it would cause your
+application code to run as root, which is not secure. However, this
+means it will not be possible to bind to port 80 or 443. Instead, a
+reverse proxy such as :doc:`nginx` or :doc:`apache-httpd` should be used
+in front of gevent.
+
+You can bind to all external IPs on a non-privileged port by using
+``0.0.0.0`` in the server arguments shown in the previous section. Don't
+do this when using a reverse proxy setup, otherwise it will be possible
+to bypass the proxy.
+
+``0.0.0.0`` is not a valid address to navigate to, you'd use a specific
+IP address in your browser.

docs/deploying/gunicorn.rst

@@ -0,0 +1,116 @@
+Gunicorn
+========
+
+`Gunicorn`_ is a pure Python WSGI server with simple configuration and
+multiple worker implementations for performance tuning.
+
+*   It tends to integrate easily with hosting platforms.
+*   It does not support Windows (but does run on WSL).
+*   It is easy to install as it does not require additional dependencies
+    or compilation.
+*   It has built-in async worker support using gevent.
+
+This page outlines the basics of running Gunicorn. Be sure to read its
+`documentation`_ and use ``gunicorn --help`` to understand what features
+are available.
+
+.. _Gunicorn: https://gunicorn.org/
+.. _documentation: https://docs.gunicorn.org/
+
+
+Installing
+----------
+
+Gunicorn is easy to install, as it does not require external
+dependencies or compilation. It runs on Windows only under WSL.
+
+Create a virtualenv, install your application, then install
+``gunicorn``.
+
+.. code-block:: text
+
+    $ cd hello-app
+    $ python -m venv .venv
+    $ . .venv/bin/activate
+    $ pip install .  # install your application
+    $ pip install gunicorn
+
+
+Running
+-------
+
+The only required argument to Gunicorn tells it how to load your Flask
+application. The syntax is ``{module_import}:{app_variable}``.
+``module_import`` is the dotted import name to the module with your
+application. ``app_variable`` is the variable with the application. It
+can also be a function call (with any arguments) if you're using the
+app factory pattern.
+
+.. code-block:: text
+
+    # equivalent to 'from hello import app'
+    $ gunicorn -w 4 'hello:app'
+
+    # equivalent to 'from hello import create_app; create_app()'
+    $ gunicorn -w 4 'hello:create_app()'
+
+    Starting gunicorn 20.1.0
+    Listening at: http://127.0.0.1:8000 (x)
+    Using worker: sync
+    Booting worker with pid: x
+    Booting worker with pid: x
+    Booting worker with pid: x
+    Booting worker with pid: x
+
+The ``-w`` option specifies the number of processes to run; a starting
+value could be ``CPU * 2``. The default is only 1 worker, which is
+probably not what you want for the default worker type.
+
+Logs for each request aren't shown by default, only worker info and
+errors are shown. To show access logs on stdout, use the
+``--access-logfile=-`` option.
+
+
+Binding Externally
+------------------
+
+Gunicorn should not be run as root because it would cause your
+application code to run as root, which is not secure. However, this
+means it will not be possible to bind to port 80 or 443. Instead, a
+reverse proxy such as :doc:`nginx` or :doc:`apache-httpd` should be used
+in front of Gunicorn.
+
+You can bind to all external IPs on a non-privileged port using the
+``-b 0.0.0.0`` option. Don't do this when using a reverse proxy setup,
+otherwise it will be possible to bypass the proxy.
+
+.. code-block:: text
+
+    $ gunicorn -w 4 -b 0.0.0.0 'hello:create_app()'
+    Listening at: http://0.0.0.0:8000 (x)
+
+``0.0.0.0`` is not a valid address to navigate to, you'd use a specific
+IP address in your browser.
+
+
+Async with gevent
+-----------------
+
+The default sync worker is appropriate for most use cases. If you need numerous,
+long running, concurrent connections, Gunicorn provides an asynchronous worker
+using `gevent`_. This is not the same as Python's ``async/await``, or the ASGI
+server spec. See :doc:`/gevent` for more information about enabling it in your
+application.
+
+.. _gevent: https://www.gevent.org/
+
+When using gevent, greenlet>=1.0 is required. When using PyPy, PyPy>=7.3.7 is
+required.
+
+.. code-block:: text
+
+    $ gunicorn -k gevent 'hello:create_app()'
+    Starting gunicorn 20.1.0
+    Listening at: http://127.0.0.1:8000 (x)
+    Using worker: gevent
+    Booting worker with pid: x

docs/deploying/index.rst

@@ -1,35 +1,78 @@
-.. _deployment:
+Deploying to Production
+=======================
 
-Deployment Options
-==================
+After developing your application, you'll want to make it available
+publicly to other users. When you're developing locally, you're probably
+using the built-in development server, debugger, and reloader. These
+should not be used in production. Instead, you should use a dedicated
+WSGI server or hosting platform, some of which will be described here.
 
-While lightweight and easy to use, **Flask's built-in server is not suitable
-for production** as it doesn't scale well.  Some of the options available for
-properly running Flask in production are documented here.
+"Production" means "not development", which applies whether you're
+serving your application publicly to millions of users or privately /
+locally to a single user. **Do not use the development server when
+deploying to production. It is intended for use only during local
+development. It is not designed to be particularly secure, stable, or
+efficient.**
 
-If you want to deploy your Flask application to a WSGI server not listed here,
-look up the server documentation about how to use a WSGI app with it.  Just
-remember that your :class:`Flask` application object is the actual WSGI
-application.
-
-
-Hosted options
---------------
-
-- `Deploying Flask on Heroku <https://devcenter.heroku.com/articles/getting-started-with-python>`_
-- `Deploying Flask on Google App Engine <https://cloud.google.com/appengine/docs/standard/python/getting-started/python-standard-env>`_
-- `Deploying Flask on AWS Elastic Beanstalk <https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/create-deploy-python-flask.html>`_
-- `Deploying on Azure (IIS) <https://docs.microsoft.com/en-us/azure/app-service/containers/how-to-configure-python>`_
-- `Deploying on PythonAnywhere <https://help.pythonanywhere.com/pages/Flask/>`_
-
-Self-hosted options
+Self-Hosted Options
 -------------------
 
-.. toctree::
-   :maxdepth: 2
+Flask is a WSGI *application*. A WSGI *server* is used to run the
+application, converting incoming HTTP requests to the standard WSGI
+environ, and converting outgoing WSGI responses to HTTP responses.
 
-   wsgi-standalone
-   uwsgi
-   mod_wsgi
-   fastcgi
-   cgi
+The primary goal of these docs is to familiarize you with the concepts
+involved in running a WSGI application using a production WSGI server
+and HTTP server. There are many WSGI servers and HTTP servers, with many
+configuration possibilities. The pages below discuss the most common
+servers, and show the basics of running each one. The next section
+discusses platforms that can manage this for you.
+
+.. toctree::
+    :maxdepth: 1
+
+    gunicorn
+    waitress
+    mod_wsgi
+    uwsgi
+    gevent
+    asgi
+
+WSGI servers have HTTP servers built-in. However, a dedicated HTTP
+server may be safer, more efficient, or more capable. Putting an HTTP
+server in front of the WSGI server is called a "reverse proxy."
+
+.. toctree::
+    :maxdepth: 1
+
+    proxy_fix
+    nginx
+    apache-httpd
+
+This list is not exhaustive, and you should evaluate these and other
+servers based on your application's needs. Different servers will have
+different capabilities, configuration, and support.
+
+
+Hosting Platforms
+-----------------
+
+There are many services available for hosting web applications without
+needing to maintain your own server, networking, domain, etc. Some
+services may have a free tier up to a certain time or bandwidth. Many of
+these services use one of the WSGI servers described above, or a similar
+interface. The links below are for some of the most common platforms,
+which have instructions for Flask, WSGI, or Python.
+
+- `PythonAnywhere <https://help.pythonanywhere.com/pages/Flask/>`_
+- `Google App Engine <https://cloud.google.com/appengine/docs/standard/python3/building-app>`_
+- `Google Cloud Run <https://cloud.google.com/run/docs/quickstarts/build-and-deploy/deploy-python-service>`_
+- `AWS Elastic Beanstalk <https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/create-deploy-python-flask.html>`_
+- `Microsoft Azure <https://docs.microsoft.com/en-us/azure/app-service/quickstart-python>`_
+
+This list is not exhaustive, and you should evaluate these and other
+services based on your application's needs. Different services will have
+different capabilities, configuration, pricing, and support.
+
+You'll probably need to :doc:`proxy_fix` when using most hosting
+platforms.

docs/deploying/mod_wsgi.rst

@@ -1,217 +1,94 @@
-.. _mod_wsgi-deployment:
+mod_wsgi
+========
 
-mod_wsgi (Apache)
-=================
+`mod_wsgi`_ is a WSGI server integrated with the `Apache httpd`_ server.
+The modern `mod_wsgi-express`_ command makes it easy to configure and
+start the server without needing to write Apache httpd configuration.
 
-If you are using the `Apache`_ webserver, consider using `mod_wsgi`_.
+*   Tightly integrated with Apache httpd.
+*   Supports Windows directly.
+*   Requires a compiler and the Apache development headers to install.
+*   Does not require a reverse proxy setup.
 
-.. admonition:: Watch Out
+This page outlines the basics of running mod_wsgi-express, not the more
+complex installation and configuration with httpd. Be sure to read the
+`mod_wsgi-express`_, `mod_wsgi`_, and `Apache httpd`_ documentation to
+understand what features are available.
 
-   Please make sure in advance that any ``app.run()`` calls you might
-   have in your application file are inside an ``if __name__ ==
-   '__main__':`` block or moved to a separate file.  Just make sure it's
-   not called because this will always start a local WSGI server which
-   we do not want if we deploy that application to mod_wsgi.
+.. _mod_wsgi-express: https://pypi.org/project/mod-wsgi/
+.. _mod_wsgi: https://modwsgi.readthedocs.io/
+.. _Apache httpd: https://httpd.apache.org/
 
-.. _Apache: https://httpd.apache.org/
 
-Installing `mod_wsgi`
----------------------
+Installing
+----------
 
-If you don't have `mod_wsgi` installed yet you have to either install it
-using a package manager or compile it yourself.  The mod_wsgi
-`installation instructions`_ cover source installations on UNIX systems.
+Installing mod_wsgi requires a compiler and the Apache server and
+development headers installed. You will get an error if they are not.
+How to install them depends on the OS and package manager that you use.
 
-If you are using Ubuntu/Debian you can apt-get it and activate it as
-follows:
+Create a virtualenv, install your application, then install
+``mod_wsgi``.
 
-.. sourcecode:: text
+.. code-block:: text
 
-    # apt-get install libapache2-mod-wsgi
+    $ cd hello-app
+    $ python -m venv .venv
+    $ . .venv/bin/activate
+    $ pip install .  # install your application
+    $ pip install mod_wsgi
 
-If you are using a yum based distribution (Fedora, OpenSUSE, etc..) you
-can install it as follows:
 
-.. sourcecode:: text
+Running
+-------
 
-    # yum install mod_wsgi
+The only argument to ``mod_wsgi-express`` specifies a script containing
+your Flask application, which must be called ``application``. You can
+write a small script to import your app with this name, or to create it
+if using the app factory pattern.
 
-On FreeBSD install `mod_wsgi` by compiling the `www/mod_wsgi` port or by
-using pkg_add:
+.. code-block:: python
+    :caption: ``wsgi.py``
 
-.. sourcecode:: text
+    from hello import app
 
-    # pkg install ap22-mod_wsgi2
+    application = app
 
-If you are using pkgsrc you can install `mod_wsgi` by compiling the
-`www/ap2-wsgi` package.
+.. code-block:: python
+    :caption: ``wsgi.py``
 
-If you encounter segfaulting child processes after the first apache
-reload you can safely ignore them.  Just restart the server.
+    from hello import create_app
 
-Creating a `.wsgi` file
------------------------
+    application = create_app()
 
-To run your application you need a :file:`yourapplication.wsgi` file.  This file
-contains the code `mod_wsgi` is executing on startup to get the application
-object.  The object called `application` in that file is then used as
-application.
+Now run the ``mod_wsgi-express start-server`` command.
 
-For most applications the following file should be sufficient::
+.. code-block:: text
 
-    from yourapplication import app as application
+    $ mod_wsgi-express start-server wsgi.py --processes 4
 
-If you don't have a factory function for application creation but a singleton
-instance you can directly import that one as `application`.
+The ``--processes`` option specifies the number of worker processes to
+run; a starting value could be ``CPU * 2``.
 
-Store that file somewhere that you will find it again (e.g.:
-:file:`/var/www/yourapplication`) and make sure that `yourapplication` and all
-the libraries that are in use are on the python load path.  If you don't
-want to install it system wide consider using a `virtual python`_
-instance.  Keep in mind that you will have to actually install your
-application into the virtualenv as well.  Alternatively there is the
-option to just patch the path in the ``.wsgi`` file before the import::
+Logs for each request aren't show in the terminal. If an error occurs,
+its information is written to the error log file shown when starting the
+server.
 
-    import sys
-    sys.path.insert(0, '/path/to/the/application')
 
-Configuring Apache
+Binding Externally
 ------------------
 
-The last thing you have to do is to create an Apache configuration file
-for your application.  In this example we are telling `mod_wsgi` to
-execute the application under a different user for security reasons:
+Unlike the other WSGI servers in these docs, mod_wsgi can be run as
+root to bind to privileged ports like 80 and 443. However, it must be
+configured to drop permissions to a different user and group for the
+worker processes.
 
-.. sourcecode:: apache
+For example, if you created a ``hello`` user and group, you should
+install your virtualenv and application as that user, then tell
+mod_wsgi to drop to that user after starting.
 
-    <VirtualHost *>
-        ServerName example.com
+.. code-block:: text
 
-        WSGIDaemonProcess yourapplication user=user1 group=group1 threads=5
-        WSGIScriptAlias / /var/www/yourapplication/yourapplication.wsgi
-
-        <Directory /var/www/yourapplication>
-            WSGIProcessGroup yourapplication
-            WSGIApplicationGroup %{GLOBAL}
-            Order deny,allow
-            Allow from all
-        </Directory>
-    </VirtualHost>
-
-Note: WSGIDaemonProcess isn't implemented in Windows and Apache will
-refuse to run with the above configuration. On a Windows system, eliminate those lines:
-
-.. sourcecode:: apache
-
-	<VirtualHost *>
-		ServerName example.com
-		WSGIScriptAlias / C:\yourdir\yourapp.wsgi
-		<Directory C:\yourdir>
-			Order deny,allow
-			Allow from all
-		</Directory>
-	</VirtualHost>
-
-Note: There have been some changes in access control configuration for `Apache 2.4`_.
-
-.. _Apache 2.4: https://httpd.apache.org/docs/trunk/upgrading.html
-
-Most notably, the syntax for directory permissions has changed from httpd 2.2
-
-.. sourcecode:: apache
-
-    Order allow,deny
-    Allow from all
-
-to httpd 2.4 syntax
-
-.. sourcecode:: apache
-
-    Require all granted
-
-
-For more information consult the `mod_wsgi documentation`_.
-
-.. _mod_wsgi: https://github.com/GrahamDumpleton/mod_wsgi
-.. _installation instructions: https://modwsgi.readthedocs.io/en/develop/installation.html
-.. _virtual python: https://pypi.org/project/virtualenv/
-.. _mod_wsgi documentation: https://modwsgi.readthedocs.io/en/develop/index.html
-
-Troubleshooting
----------------
-
-If your application does not run, follow this guide to troubleshoot:
-
-**Problem:** application does not run, errorlog shows SystemExit ignored
-    You have an ``app.run()`` call in your application file that is not
-    guarded by an ``if __name__ == '__main__':`` condition.  Either
-    remove that :meth:`~flask.Flask.run` call from the file and move it
-    into a separate :file:`run.py` file or put it into such an if block.
-
-**Problem:** application gives permission errors
-    Probably caused by your application running as the wrong user.  Make
-    sure the folders the application needs access to have the proper
-    privileges set and the application runs as the correct user
-    (``user`` and ``group`` parameter to the `WSGIDaemonProcess`
-    directive)
-
-**Problem:** application dies with an error on print
-    Keep in mind that mod_wsgi disallows doing anything with
-    :data:`sys.stdout` and :data:`sys.stderr`.  You can disable this
-    protection from the config by setting the `WSGIRestrictStdout` to
-    ``off``:
-
-    .. sourcecode:: apache
-
-        WSGIRestrictStdout Off
-
-    Alternatively you can also replace the standard out in the .wsgi file
-    with a different stream::
-
-        import sys
-        sys.stdout = sys.stderr
-
-**Problem:** accessing resources gives IO errors
-    Your application probably is a single .py file you symlinked into
-    the site-packages folder.  Please be aware that this does not work,
-    instead you either have to put the folder into the pythonpath the
-    file is stored in, or convert your application into a package.
-
-    The reason for this is that for non-installed packages, the module
-    filename is used to locate the resources and for symlinks the wrong
-    filename is picked up.
-
-Support for Automatic Reloading
--------------------------------
-
-To help deployment tools you can activate support for automatic
-reloading.  Whenever something changes the ``.wsgi`` file, `mod_wsgi` will
-reload all the daemon processes for us.
-
-For that, just add the following directive to your `Directory` section:
-
-.. sourcecode:: apache
-
-   WSGIScriptReloading On
-
-Working with Virtual Environments
----------------------------------
-
-Virtual environments have the advantage that they never install the
-required dependencies system wide so you have a better control over what
-is used where.  If you want to use a virtual environment with mod_wsgi
-you have to modify your ``.wsgi`` file slightly.
-
-Add the following lines to the top of your ``.wsgi`` file::
-
-    activate_this = '/path/to/env/bin/activate_this.py'
-    execfile(activate_this, dict(__file__=activate_this))
-
-For Python 3 add the following lines to the top of your ``.wsgi`` file::
-
-    activate_this = '/path/to/env/bin/activate_this.py'
-    with open(activate_this) as file_:
-        exec(file_.read(), dict(__file__=activate_this))
-
-This sets up the load paths according to the settings of the virtual
-environment.  Keep in mind that the path has to be absolute.
+    $ sudo /home/hello/.venv/bin/mod_wsgi-express start-server \
+        /home/hello/wsgi.py \
+        --user hello --group hello --port 80 --processes 4

docs/deploying/nginx.rst

@@ -0,0 +1,69 @@
+nginx
+=====
+
+`nginx`_ is a fast, production level HTTP server. When serving your
+application with one of the WSGI servers listed in :doc:`index`, it is
+often good or necessary to put a dedicated HTTP server in front of it.
+This "reverse proxy" can handle incoming requests, TLS, and other
+security and performance concerns better than the WSGI server.
+
+Nginx can be installed using your system package manager, or a pre-built
+executable for Windows. Installing and running Nginx itself is outside
+the scope of this doc. This page outlines the basics of configuring
+Nginx to proxy your application. Be sure to read its documentation to
+understand what features are available.
+
+.. _nginx: https://nginx.org/
+
+
+Domain Name
+-----------
+
+Acquiring and configuring a domain name is outside the scope of this
+doc. In general, you will buy a domain name from a registrar, pay for
+server space with a hosting provider, and then point your registrar
+at the hosting provider's name servers.
+
+To simulate this, you can also edit your ``hosts`` file, located at
+``/etc/hosts`` on Linux. Add a line that associates a name with the
+local IP.
+
+Modern Linux systems may be configured to treat any domain name that
+ends with ``.localhost`` like this without adding it to the ``hosts``
+file.
+
+.. code-block:: python
+    :caption: ``/etc/hosts``
+
+    127.0.0.1 hello.localhost
+
+
+Configuration
+-------------
+
+The nginx configuration is located at ``/etc/nginx/nginx.conf`` on
+Linux. It may be different depending on your operating system. Check the
+docs and look for ``nginx.conf``.
+
+Remove or comment out any existing ``server`` section. Add a ``server``
+section and use the ``proxy_pass`` directive to point to the address the
+WSGI server is listening on. We'll assume the WSGI server is listening
+locally at ``http://127.0.0.1:8000``.
+
+.. code-block:: nginx
+    :caption: ``/etc/nginx.conf``
+
+    server {
+        listen 80;
+        server_name _;
+
+        location / {
+            proxy_pass http://127.0.0.1:8000/;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+            proxy_set_header X-Forwarded-Proto $scheme;
+            proxy_set_header X-Forwarded-Host $host;
+            proxy_set_header X-Forwarded-Prefix /;
+        }
+    }
+
+Then :doc:`proxy_fix` so that your application uses these headers.

docs/deploying/proxy_fix.rst

@@ -0,0 +1,33 @@
+Tell Flask it is Behind a Proxy
+===============================
+
+When using a reverse proxy, or many Python hosting platforms, the proxy
+will intercept and forward all external requests to the local WSGI
+server.
+
+From the WSGI server and Flask application's perspectives, requests are
+now coming from the HTTP server to the local address, rather than from
+the remote address to the external server address.
+
+HTTP servers should set ``X-Forwarded-`` headers to pass on the real
+values to the application. The application can then be told to trust and
+use those values by wrapping it with the
+:doc:`werkzeug:middleware/proxy_fix` middleware provided by Werkzeug.
+
+This middleware should only be used if the application is actually
+behind a proxy, and should be configured with the number of proxies that
+are chained in front of it. Not all proxies set all the headers. Since
+incoming headers can be faked, you must set how many proxies are setting
+each header so the middleware knows what to trust.
+
+.. code-block:: python
+
+    from werkzeug.middleware.proxy_fix import ProxyFix
+
+    app.wsgi_app = ProxyFix(
+        app.wsgi_app, x_for=1, x_proto=1, x_host=1, x_prefix=1
+    )
+
+Remember, only apply this middleware if you are behind a proxy, and set
+the correct number of proxies that set each header. It can be a security
+issue if you get this configuration wrong.

docs/deploying/uwsgi.rst

@@ -1,72 +1,143 @@
-.. _deploying-uwsgi:
-
 uWSGI
 =====
 
-uWSGI is a deployment option on servers like `nginx`_, `lighttpd`_, and
-`cherokee`_; see :ref:`deploying-fastcgi` and :ref:`deploying-wsgi-standalone`
-for other options.  To use your WSGI application with uWSGI protocol you will
-need a uWSGI server first. uWSGI is both a protocol and an application server;
-the application server can serve uWSGI, FastCGI, and HTTP protocols.
+`uWSGI`_ is a fast, compiled server suite with extensive configuration
+and capabilities beyond a basic server.
 
-The most popular uWSGI server is `uwsgi`_, which we will use for this
-guide.  Make sure to have it installed to follow along.
+*   It can be very performant due to being a compiled program.
+*   It is complex to configure beyond the basic application, and has so
+    many options that it can be difficult for beginners to understand.
+*   It does not support Windows (but does run on WSL).
+*   It requires a compiler to install in some cases.
 
-.. admonition:: Watch Out
+This page outlines the basics of running uWSGI. Be sure to read its
+documentation to understand what features are available.
 
-   Please make sure in advance that any ``app.run()`` calls you might
-   have in your application file are inside an ``if __name__ ==
-   '__main__':`` block or moved to a separate file.  Just make sure it's
-   not called because this will always start a local WSGI server which
-   we do not want if we deploy that application to uWSGI.
+.. _uWSGI: https://uwsgi-docs.readthedocs.io/en/latest/
 
-Starting your app with uwsgi
-----------------------------
 
-`uwsgi` is designed to operate on WSGI callables found in python modules.
+Installing
+----------
 
-Given a flask application in myapp.py, use the following command:
+uWSGI has multiple ways to install it. The most straightforward is to
+install the ``pyuwsgi`` package, which provides precompiled wheels for
+common platforms. However, it does not provide SSL support, which can be
+provided with a reverse proxy instead.
 
-.. sourcecode:: text
+Create a virtualenv, install your application, then install ``pyuwsgi``.
 
-    $ uwsgi -s /tmp/yourapplication.sock --manage-script-name --mount /yourapplication=myapp:app
+.. code-block:: text
 
-The ``--manage-script-name`` will move the handling of ``SCRIPT_NAME`` to uwsgi,
-since its smarter about that. It is used together with the ``--mount`` directive
-which will make requests to ``/yourapplication`` be directed to ``myapp:app``.
-If your application is accessible at root level, you can use a single ``/``
-instead of ``/yourapplication``. ``myapp`` refers to the name of the file of
-your flask application (without extension) or the module which provides ``app``.
-``app`` is the callable inside of your application (usually the line reads
-``app = Flask(__name__)``.
+    $ cd hello-app
+    $ python -m venv .venv
+    $ . .venv/bin/activate
+    $ pip install .  # install your application
+    $ pip install pyuwsgi
 
-If you want to deploy your flask application inside of a virtual environment,
-you need to also add ``--virtualenv /path/to/virtual/environment``. You might
-also need to add ``--plugin python`` or ``--plugin python3`` depending on which
-python version you use for your project.
+If you have a compiler available, you can install the ``uwsgi`` package
+instead. Or install the ``pyuwsgi`` package from sdist instead of wheel.
+Either method will include SSL support.
 
-Configuring nginx
+.. code-block:: text
+
+    $ pip install uwsgi
+
+    # or
+    $ pip install --no-binary pyuwsgi pyuwsgi
+
+
+Running
+-------
+
+The most basic way to run uWSGI is to tell it to start an HTTP server
+and import your application.
+
+.. code-block:: text
+
+    $ uwsgi --http 127.0.0.1:8000 --master -p 4 -w hello:app
+
+    *** Starting uWSGI 2.0.20 (64bit) on [x] ***
+    *** Operational MODE: preforking ***
+    mounting hello:app on /
+    spawned uWSGI master process (pid: x)
+    spawned uWSGI worker 1 (pid: x, cores: 1)
+    spawned uWSGI worker 2 (pid: x, cores: 1)
+    spawned uWSGI worker 3 (pid: x, cores: 1)
+    spawned uWSGI worker 4 (pid: x, cores: 1)
+    spawned uWSGI http 1 (pid: x)
+
+If you're using the app factory pattern, you'll need to create a small
+Python file to create the app, then point uWSGI at that.
+
+.. code-block:: python
+    :caption: ``wsgi.py``
+
+    from hello import create_app
+
+    app = create_app()
+
+.. code-block:: text
+
+    $ uwsgi --http 127.0.0.1:8000 --master -p 4 -w wsgi:app
+
+The ``--http`` option starts an HTTP server at 127.0.0.1 port 8000. The
+``--master`` option specifies the standard worker manager. The ``-p``
+option starts 4 worker processes; a starting value could be ``CPU * 2``.
+The ``-w`` option tells uWSGI how to import your application
+
+
+Binding Externally
+------------------
+
+uWSGI should not be run as root with the configuration shown in this doc
+because it would cause your application code to run as root, which is
+not secure. However, this means it will not be possible to bind to port
+80 or 443. Instead, a reverse proxy such as :doc:`nginx` or
+:doc:`apache-httpd` should be used in front of uWSGI. It is possible to
+run uWSGI as root securely, but that is beyond the scope of this doc.
+
+uWSGI has optimized integration with `Nginx uWSGI`_ and
+`Apache mod_proxy_uwsgi`_, and possibly other servers, instead of using
+a standard HTTP proxy. That configuration is beyond the scope of this
+doc, see the links for more information.
+
+.. _Nginx uWSGI: https://uwsgi-docs.readthedocs.io/en/latest/Nginx.html
+.. _Apache mod_proxy_uwsgi: https://uwsgi-docs.readthedocs.io/en/latest/Apache.html#mod-proxy-uwsgi
+
+You can bind to all external IPs on a non-privileged port using the
+``--http 0.0.0.0:8000`` option. Don't do this when using a reverse proxy
+setup, otherwise it will be possible to bypass the proxy.
+
+.. code-block:: text
+
+    $ uwsgi --http 0.0.0.0:8000 --master -p 4 -w wsgi:app
+
+``0.0.0.0`` is not a valid address to navigate to, you'd use a specific
+IP address in your browser.
+
+
+Async with gevent
 -----------------
 
-A basic flask nginx configuration looks like this::
+The default sync worker is appropriate for most use cases. If you need numerous,
+long running, concurrent connections, uWSGI provides an asynchronous worker
+using `gevent`_. This is not the same as Python's ``async/await``, or the ASGI
+server spec. See :doc:`/gevent` for more information about enabling it in your
+application.
 
-    location = /yourapplication { rewrite ^ /yourapplication/; }
-    location /yourapplication { try_files $uri @yourapplication; }
-    location @yourapplication {
-      include uwsgi_params;
-      uwsgi_pass unix:/tmp/yourapplication.sock;
-    }
+.. _gevent: https://www.gevent.org/
 
-This configuration binds the application to ``/yourapplication``.  If you want
-to have it in the URL root its a bit simpler::
+When using gevent, greenlet>=1.0 is required. When using PyPy, PyPy>=7.3.7 is
+required.
 
-    location / { try_files $uri @yourapplication; }
-    location @yourapplication {
-        include uwsgi_params;
-        uwsgi_pass unix:/tmp/yourapplication.sock;
-    }
+.. code-block:: text
 
-.. _nginx: https://nginx.org/
-.. _lighttpd: https://www.lighttpd.net/
-.. _cherokee: http://cherokee-project.com/
-.. _uwsgi: https://uwsgi-docs.readthedocs.io/en/latest/
+    $ uwsgi --http 127.0.0.1:8000 --master --gevent 100 -w wsgi:app
+
+    *** Starting uWSGI 2.0.20 (64bit) on [x] ***
+    *** Operational MODE: async ***
+    mounting hello:app on /
+    spawned uWSGI master process (pid: x)
+    spawned uWSGI worker 1 (pid: x, cores: 100)
+    spawned uWSGI http 1 (pid: x)
+    *** running gevent loop engine [addr:x] ***

docs/deploying/waitress.rst

@@ -0,0 +1,75 @@
+Waitress
+========
+
+`Waitress`_ is a pure Python WSGI server.
+
+*   It is easy to configure.
+*   It supports Windows directly.
+*   It is easy to install as it does not require additional dependencies
+    or compilation.
+*   It does not support streaming requests, full request data is always
+    buffered.
+*   It uses a single process with multiple thread workers.
+
+This page outlines the basics of running Waitress. Be sure to read its
+documentation and ``waitress-serve --help`` to understand what features
+are available.
+
+.. _Waitress: https://docs.pylonsproject.org/projects/waitress/
+
+
+Installing
+----------
+
+Create a virtualenv, install your application, then install
+``waitress``.
+
+.. code-block:: text
+
+    $ cd hello-app
+    $ python -m venv .venv
+    $ . .venv/bin/activate
+    $ pip install .  # install your application
+    $ pip install waitress
+
+
+Running
+-------
+
+The only required argument to ``waitress-serve`` tells it how to load
+your Flask application. The syntax is ``{module}:{app}``. ``module`` is
+the dotted import name to the module with your application. ``app`` is
+the variable with the application. If you're using the app factory
+pattern, use ``--call {module}:{factory}`` instead.
+
+.. code-block:: text
+
+    # equivalent to 'from hello import app'
+    $ waitress-serve --host 127.0.0.1 hello:app
+
+    # equivalent to 'from hello import create_app; create_app()'
+    $ waitress-serve --host 127.0.0.1 --call hello:create_app
+
+    Serving on http://127.0.0.1:8080
+
+The ``--host`` option binds the server to local ``127.0.0.1`` only.
+
+Logs for each request aren't shown, only errors are shown. Logging can
+be configured through the Python interface instead of the command line.
+
+
+Binding Externally
+------------------
+
+Waitress should not be run as root because it would cause your
+application code to run as root, which is not secure. However, this
+means it will not be possible to bind to port 80 or 443. Instead, a
+reverse proxy such as :doc:`nginx` or :doc:`apache-httpd` should be used
+in front of Waitress.
+
+You can bind to all external IPs on a non-privileged port by not
+specifying the ``--host`` option. Don't do this when using a reverse
+proxy setup, otherwise it will be possible to bypass the proxy.
+
+``0.0.0.0`` is not a valid address to navigate to, you'd use a specific
+IP address in your browser.

docs/deploying/wsgi-standalone.rst

@@ -1,155 +0,0 @@
-.. _deploying-wsgi-standalone:
-
-Standalone WSGI Containers
-==========================
-
-There are popular servers written in Python that contain WSGI applications and
-serve HTTP.  These servers stand alone when they run; you can proxy to them
-from your web server.  Note the section on :ref:`deploying-proxy-setups` if you
-run into issues.
-
-Gunicorn
---------
-
-`Gunicorn`_ 'Green Unicorn' is a WSGI HTTP Server for UNIX. It's a pre-fork
-worker model ported from Ruby's Unicorn project. It supports both `eventlet`_
-and `greenlet`_. Running a Flask application on this server is quite simple::
-
-    gunicorn myproject:app
-
-`Gunicorn`_ provides many command-line options -- see ``gunicorn -h``.
-For example, to run a Flask application with 4 worker processes (``-w
-4``) binding to localhost port 4000 (``-b 127.0.0.1:4000``)::
-
-    gunicorn -w 4 -b 127.0.0.1:4000 myproject:app
-
-The ``gunicorn`` command expects the names of your application module or
-package and the application instance within the module. If you use the
-application factory pattern, you can pass a call to that::
-
-    $ gunicorn "myproject:create_app()"
-
-.. _Gunicorn: https://gunicorn.org/
-.. _eventlet: https://eventlet.net/
-
-
-uWSGI
---------
-
-`uWSGI`_ is a fast application server written in C. It is very configurable
-which makes it more complicated to setup than gunicorn.
-
-Running `uWSGI HTTP Router`_::
-
-    uwsgi --http 127.0.0.1:5000 --module myproject:app
-
-For a more optimized setup, see :doc:`/deploying/uwsgi`.
-
-.. _uWSGI: https://uwsgi-docs.readthedocs.io/en/latest/
-.. _uWSGI HTTP Router: https://uwsgi-docs.readthedocs.io/en/latest/HTTP.html#the-uwsgi-http-https-router
-
-Gevent
--------
-
-`Gevent`_ is a coroutine-based Python networking library that uses
-`greenlet`_ to provide a high-level synchronous API on top of `libev`_
-event loop::
-
-    from gevent.wsgi import WSGIServer
-    from yourapplication import app
-
-    http_server = WSGIServer(('', 5000), app)
-    http_server.serve_forever()
-
-.. _Gevent: http://www.gevent.org/
-.. _greenlet: https://greenlet.readthedocs.io/en/latest/
-.. _libev: http://software.schmorp.de/pkg/libev.html
-
-Twisted Web
------------
-
-`Twisted Web`_ is the web server shipped with `Twisted`_, a mature,
-non-blocking event-driven networking library. Twisted Web comes with a
-standard WSGI container which can be controlled from the command line using
-the ``twistd`` utility::
-
-    twistd web --wsgi myproject.app
-
-This example will run a Flask application called ``app`` from a module named
-``myproject``.
-
-Twisted Web supports many flags and options, and the ``twistd`` utility does
-as well; see ``twistd -h`` and ``twistd web -h`` for more information. For
-example, to run a Twisted Web server in the foreground, on port 8080, with an
-application from ``myproject``::
-
-    twistd -n web --port tcp:8080 --wsgi myproject.app
-
-.. _Twisted: https://twistedmatrix.com/trac/
-.. _Twisted Web: https://twistedmatrix.com/trac/wiki/TwistedWeb
-
-.. _deploying-proxy-setups:
-
-Proxy Setups
-------------
-
-If you deploy your application using one of these servers behind an HTTP proxy
-you will need to rewrite a few headers in order for the application to work.
-The two problematic values in the WSGI environment usually are ``REMOTE_ADDR``
-and ``HTTP_HOST``.  You can configure your httpd to pass these headers, or you
-can fix them in middleware.  Werkzeug ships a fixer that will solve some common
-setups, but you might want to write your own WSGI middleware for specific
-setups.
-
-Here's a simple nginx configuration which proxies to an application served on
-localhost at port 8000, setting appropriate headers:
-
-.. sourcecode:: nginx
-
-    server {
-        listen 80;
-
-        server_name _;
-
-        access_log  /var/log/nginx/access.log;
-        error_log  /var/log/nginx/error.log;
-
-        location / {
-            proxy_pass         http://127.0.0.1:8000/;
-            proxy_redirect     off;
-
-            proxy_set_header   Host                 $host;
-            proxy_set_header   X-Real-IP            $remote_addr;
-            proxy_set_header   X-Forwarded-For      $proxy_add_x_forwarded_for;
-            proxy_set_header   X-Forwarded-Proto    $scheme;
-        }
-    }
-
-If your httpd is not providing these headers, the most common setup invokes the
-host being set from ``X-Forwarded-Host`` and the remote address from
-``X-Forwarded-For``::
-
-    from werkzeug.middleware.proxy_fix import ProxyFix
-    app.wsgi_app = ProxyFix(app.wsgi_app, x_proto=1, x_host=1)
-
-.. admonition:: Trusting Headers
-
-   Please keep in mind that it is a security issue to use such a middleware in
-   a non-proxy setup because it will blindly trust the incoming headers which
-   might be forged by malicious clients.
-
-If you want to rewrite the headers from another header, you might want to
-use a fixer like this::
-
-    class CustomProxyFix(object):
-
-        def __init__(self, app):
-            self.app = app
-
-        def __call__(self, environ, start_response):
-            host = environ.get('HTTP_X_FHOST', '')
-            if host:
-                environ['HTTP_HOST'] = host
-            return self.app(environ, start_response)
-
-    app.wsgi_app = CustomProxyFix(app.wsgi_app)

docs/design.rst

@@ -1,5 +1,3 @@
-.. _design:
-
 Design Decisions in Flask
 =========================
 
@@ -77,7 +75,7 @@ to the application object :meth:`~flask.Flask.wsgi_app`).
 
 Furthermore this design makes it possible to use a factory function to
 create the application which is very helpful for unit testing and similar
-things (:ref:`app-factories`).
+things (:doc:`/patterns/appfactories`).
 
 The Routing System
 ------------------
@@ -98,10 +96,10 @@ is ambiguous.
 One Template Engine
 -------------------
 
-Flask decides on one template engine: Jinja2.  Why doesn't Flask have a
+Flask decides on one template engine: Jinja.  Why doesn't Flask have a
 pluggable template engine interface?  You can obviously use a different
-template engine, but Flask will still configure Jinja2 for you.  While
-that limitation that Jinja2 is *always* configured will probably go away,
+template engine, but Flask will still configure Jinja for you.  While
+that limitation that Jinja is *always* configured will probably go away,
 the decision to bundle one template engine and use that will not.
 
 Template engines are like programming languages and each of those engines
@@ -109,19 +107,19 @@ has a certain understanding about how things work.  On the surface they
 all work the same: you tell the engine to evaluate a template with a set
 of variables and take the return value as string.
 
-But that's about where similarities end.  Jinja2 for example has an
-extensive filter system, a certain way to do template inheritance, support
-for reusable blocks (macros) that can be used from inside templates and
-also from Python code, uses Unicode for all operations, supports
-iterative template rendering, configurable syntax and more.  On the other
-hand an engine like Genshi is based on XML stream evaluation, template
-inheritance by taking the availability of XPath into account and more.
-Mako on the other hand treats templates similar to Python modules.
+But that's about where similarities end. Jinja for example has an
+extensive filter system, a certain way to do template inheritance,
+support for reusable blocks (macros) that can be used from inside
+templates and also from Python code, supports iterative template
+rendering, configurable syntax and more. On the other hand an engine
+like Genshi is based on XML stream evaluation, template inheritance by
+taking the availability of XPath into account and more. Mako on the
+other hand treats templates similar to Python modules.
 
 When it comes to connecting a template engine with an application or
 framework there is more than just rendering templates.  For instance,
-Flask uses Jinja2's extensive autoescaping support.  Also it provides
-ways to access macros from Jinja2 templates.
+Flask uses Jinja's extensive autoescaping support.  Also it provides
+ways to access macros from Jinja templates.
 
 A template abstraction layer that would not take the unique features of
 the template engines away is a science on its own and a too large
@@ -132,11 +130,27 @@ being present.  You can easily use your own templating language, but an
 extension could still depend on Jinja itself.
 
 
-Micro with Dependencies
+What does "micro" mean?
 -----------------------
 
+“Micro” does not mean that your whole web application has to fit into a single
+Python file (although it certainly can), nor does it mean that Flask is lacking
+in functionality. The "micro" in microframework means Flask aims to keep the
+core simple but extensible. Flask won't make many decisions for you, such as
+what database to use. Those decisions that it does make, such as what
+templating engine to use, are easy to change.  Everything else is up to you, so
+that Flask can be everything you need and nothing you don't.
+
+By default, Flask does not include a database abstraction layer, form
+validation or anything else where different libraries already exist that can
+handle that. Instead, Flask supports extensions to add such functionality to
+your application as if it was implemented in Flask itself. Numerous extensions
+provide database integration, form validation, upload handling, various open
+authentication technologies, and more. Flask may be "micro", but it's ready for
+production use on a variety of needs.
+
 Why does Flask call itself a microframework and yet it depends on two
-libraries (namely Werkzeug and Jinja2).  Why shouldn't it?  If we look
+libraries (namely Werkzeug and Jinja).  Why shouldn't it?  If we look
 over to the Ruby side of web development there we have a protocol very
 similar to WSGI.  Just that it's called Rack there, but besides that it
 looks very much like a WSGI rendition for Ruby.  But nearly all
@@ -155,22 +169,39 @@ infrastructure, packages with dependencies are no longer an issue and
 there are very few reasons against having libraries that depend on others.
 
 
-Thread Locals
--------------
+Context Locals
+--------------
 
-Flask uses thread local objects (context local objects in fact, they
-support greenlet contexts as well) for request, session and an extra
-object you can put your own things on (:data:`~flask.g`).  Why is that and
-isn't that a bad idea?
+Flask uses special context locals and proxies to provide access to the
+current app and request data to any code running during a request, CLI command,
+etc. Context locals are specific to the worker handling the activity, such as a
+thread, process, coroutine, or greenlet.
 
-Yes it is usually not such a bright idea to use thread locals.  They cause
-troubles for servers that are not based on the concept of threads and make
-large applications harder to maintain.  However Flask is just not designed
-for large applications or asynchronous servers.  Flask wants to make it
-quick and easy to write a traditional web application.
+The context and proxies help solve two development issues: circular imports, and
+passing around global data. :data:`.current_app` can be used to access the
+application object without needing to import the app object directly, avoiding
+circular import issues. :data:`.request`, :data:`.session`, and :data:`.g` can
+be imported to access the current data for the request, rather than needing to
+pass them as arguments through every single function in your project.
 
-Also see the :ref:`becomingbig` section of the documentation for some
-inspiration for larger applications based on Flask.
+
+Async/await and ASGI support
+----------------------------
+
+Flask supports ``async`` coroutines for view functions by executing the
+coroutine on a separate thread instead of using an event loop on the
+main thread as an async-first (ASGI) framework would. This is necessary
+for Flask to remain backwards compatible with extensions and code built
+before ``async`` was introduced into Python. This compromise introduces
+a performance cost compared with the ASGI frameworks, due to the
+overhead of the threads.
+
+Due to how tied to WSGI Flask's code is, it's not clear if it's possible
+to make the ``Flask`` class support ASGI and WSGI at the same time. Work
+is currently being done in Werkzeug to work with ASGI, which may
+eventually enable support in Flask as well.
+
+See :doc:`/async-await` for more discussion.
 
 
 What Flask is, What Flask is Not
@@ -178,7 +209,7 @@ What Flask is, What Flask is Not
 
 Flask will never have a database layer.  It will not have a form library
 or anything else in that direction.  Flask itself just bridges to Werkzeug
-to implement a proper WSGI application and to Jinja2 to handle templating.
+to implement a proper WSGI application and to Jinja to handle templating.
 It also binds to a few common standard library packages such as logging.
 Everything else is up for extensions.
 
@@ -187,5 +218,12 @@ requirements and Flask could not meet those if it would force any of this
 into the core.  The majority of web applications will need a template
 engine in some sort.  However not every application needs a SQL database.
 
+As your codebase grows, you are free to make the design decisions appropriate
+for your project.  Flask will continue to provide a very simple glue layer to
+the best that Python has to offer.  You can implement advanced patterns in
+SQLAlchemy or another database tool, introduce non-relational data persistence
+as appropriate, and take advantage of framework-agnostic tools built for WSGI,
+the Python web interface.
+
 The idea of Flask is to build a good foundation for all applications.
 Everything else is up to you or extensions.

docs/errorhandling.rst

@@ -1,14 +1,10 @@
-.. _application-errors:
+Handling Application Errors
+===========================
 
-Application Errors
-==================
-
-.. versionadded:: 0.3
-
-Applications fail, servers fail.  Sooner or later you will see an exception
-in production.  Even if your code is 100% correct, you will still see
-exceptions from time to time.  Why?  Because everything else involved will
-fail.  Here are some situations where perfectly fine code can lead to server
+Applications fail, servers fail. Sooner or later you will see an exception
+in production. Even if your code is 100% correct, you will still see
+exceptions from time to time. Why? Because everything else involved will
+fail. Here are some situations where perfectly fine code can lead to server
 errors:
 
 -   the client terminated the request early and the application was still
@@ -20,13 +16,16 @@ errors:
 -   a programming error in a library you are using
 -   network connection of the server to another system failed
 
-And that's just a small sample of issues you could be facing.  So how do we
-deal with that sort of problem?  By default if your application runs in
-production mode, Flask will display a very simple page for you and log the
-exception to the :attr:`~flask.Flask.logger`.
+And that's just a small sample of issues you could be facing. So how do we
+deal with that sort of problem? By default if your application runs in
+production mode, and an exception is raised Flask will display a very simple
+page for you and log the exception to the :attr:`~flask.Flask.logger`.
 
 But there is more you can do, and we will cover some better setups to deal
-with errors.
+with errors including custom exceptions and 3rd party tools.
+
+
+.. _error-logging-tools:
 
 Error Logging Tools
 -------------------
@@ -34,51 +33,66 @@ Error Logging Tools
 Sending error mails, even if just for critical ones, can become
 overwhelming if enough users are hitting the error and log files are
 typically never looked at. This is why we recommend using `Sentry
-<https://sentry.io/welcome/>`_ for dealing with application errors.  It's
-available as an Open Source project `on GitHub
-<https://github.com/getsentry/sentry>`__ and is also available as a `hosted version
+<https://sentry.io/>`_ for dealing with application errors. It's
+available as a source-available project `on GitHub
+<https://github.com/getsentry/sentry>`_ and is also available as a `hosted version
 <https://sentry.io/signup/>`_ which you can try for free. Sentry
 aggregates duplicate errors, captures the full stack trace and local
 variables for debugging, and sends you mails based on new errors or
 frequency thresholds.
 
-To use Sentry you need to install the `raven` client with extra `flask` dependencies::
+To use Sentry you need to install the ``sentry-sdk`` client with extra
+``flask`` dependencies.
 
-    $ pip install raven[flask]
+.. code-block:: text
 
-And then add this to your Flask app::
+    $ pip install sentry-sdk[flask]
 
-    from raven.contrib.flask import Sentry
-    sentry = Sentry(app, dsn='YOUR_DSN_HERE')
+And then add this to your Flask app:
 
-Or if you are using factories you can also init it later::
+.. code-block:: python
 
-    from raven.contrib.flask import Sentry
-    sentry = Sentry(dsn='YOUR_DSN_HERE')
+    import sentry_sdk
+    from sentry_sdk.integrations.flask import FlaskIntegration
 
-    def create_app():
-        app = Flask(__name__)
-        sentry.init_app(app)
-        ...
-        return app
+    sentry_sdk.init('YOUR_DSN_HERE', integrations=[FlaskIntegration()])
 
-The `YOUR_DSN_HERE` value needs to be replaced with the DSN value you get
-from your Sentry installation.
+The ``YOUR_DSN_HERE`` value needs to be replaced with the DSN value you
+get from your Sentry installation.
 
-Afterwards failures are automatically reported to Sentry and from there
-you can receive error notifications.
+After installation, failures leading to an Internal Server Error
+are automatically reported to Sentry and from there you can
+receive error notifications.
 
-.. _error-handlers:
+See also:
 
-Error handlers
+-   Sentry also supports catching errors from a worker queue
+    (RQ, Celery, etc.) in a similar fashion. See the `Python SDK docs
+    <https://docs.sentry.io/platforms/python/>`__ for more information.
+-   `Flask-specific documentation <https://docs.sentry.io/platforms/python/guides/flask/>`__
+
+
+Error Handlers
 --------------
 
+When an error occurs in Flask, an appropriate `HTTP status code
+<https://developer.mozilla.org/en-US/docs/Web/HTTP/Status>`__ will be
+returned. 400-499 indicate errors with the client's request data, or
+about the data requested. 500-599 indicate errors with the server or
+application itself.
+
 You might want to show custom error pages to the user when an error occurs.
 This can be done by registering error handlers.
 
-An error handler is a normal view function that return a response, but instead
-of being registered for a route, it is registered for an exception or HTTP
-status code that would is raised while trying to handle a request.
+An error handler is a function that returns a response when a type of error is
+raised, similar to how a view is a function that returns a response when a
+request URL is matched. It is passed the instance of the error being handled,
+which is most likely a :exc:`~werkzeug.exceptions.HTTPException`.
+
+The status code of the response will not be set to the handler's code. Make
+sure to provide the appropriate HTTP status code when returning a response from
+a handler.
+
 
 Registering
 ```````````
@@ -86,7 +100,9 @@ Registering
 Register handlers by decorating a function with
 :meth:`~flask.Flask.errorhandler`. Or use
 :meth:`~flask.Flask.register_error_handler` to register the function later.
-Remember to set the error code when returning the response. ::
+Remember to set the error code when returning the response.
+
+.. code-block:: python
 
     @app.errorhandler(werkzeug.exceptions.BadRequest)
     def handle_bad_request(e):
@@ -102,13 +118,15 @@ when registering handlers. (``BadRequest.code == 400``)
 Non-standard HTTP codes cannot be registered by code because they are not known
 by Werkzeug. Instead, define a subclass of
 :class:`~werkzeug.exceptions.HTTPException` with the appropriate code and
-register and raise that exception class. ::
+register and raise that exception class.
+
+.. code-block:: python
 
     class InsufficientStorage(werkzeug.exceptions.HTTPException):
         code = 507
         description = 'Not enough storage space.'
 
-    app.register_error_handler(InsuffcientStorage, handle_507)
+    app.register_error_handler(InsufficientStorage, handle_507)
 
     raise InsufficientStorage()
 
@@ -117,20 +135,36 @@ Handlers can be registered for any exception class, not just
 codes. Handlers can be registered for a specific class, or for all subclasses
 of a parent class.
 
+
 Handling
 ````````
 
-When an exception is caught by Flask while handling a request, it is first
-looked up by code. If no handler is registered for the code, it is looked up
-by its class hierarchy; the most specific handler is chosen. If no handler is
-registered, :class:`~werkzeug.exceptions.HTTPException` subclasses show a
-generic message about their code, while other exceptions are converted to a
-generic 500 Internal Server Error.
+When building a Flask application you *will* run into exceptions. If some part
+of your code breaks while handling a request (and you have no error handlers
+registered), a "500 Internal Server Error"
+(:exc:`~werkzeug.exceptions.InternalServerError`) will be returned by default.
+Similarly, "404 Not Found"
+(:exc:`~werkzeug.exceptions.NotFound`) error will occur if a request is sent to an unregistered route.
+If a route receives an unallowed request method, a "405 Method Not Allowed"
+(:exc:`~werkzeug.exceptions.MethodNotAllowed`) will be raised. These are all
+subclasses of :class:`~werkzeug.exceptions.HTTPException` and are provided by
+default in Flask.
 
-For example, if an instance of :exc:`ConnectionRefusedError` is raised, and a handler
-is registered for :exc:`ConnectionError` and :exc:`ConnectionRefusedError`,
-the more specific :exc:`ConnectionRefusedError` handler is called with the
-exception instance to generate the response.
+Flask gives you the ability to raise any HTTP exception registered by
+Werkzeug. However, the default HTTP exceptions return simple exception
+pages. You might want to show custom error pages to the user when an error occurs.
+This can be done by registering error handlers.
+
+When Flask catches an exception while handling a request, it is first looked up by code.
+If no handler is registered for the code, Flask looks up the error by its class hierarchy; the most specific handler is chosen.
+If no handler is registered, :class:`~werkzeug.exceptions.HTTPException` subclasses show a
+generic message about their code, while other exceptions are converted to a
+generic "500 Internal Server Error".
+
+For example, if an instance of :exc:`ConnectionRefusedError` is raised,
+and a handler is registered for :exc:`ConnectionError` and
+:exc:`ConnectionRefusedError`, the more specific :exc:`ConnectionRefusedError`
+handler is called with the exception instance to generate the response.
 
 Handlers registered on the blueprint take precedence over those registered
 globally on the application, assuming a blueprint is handling the request that
@@ -138,78 +172,352 @@ raises the exception. However, the blueprint cannot handle 404 routing errors
 because the 404 occurs at the routing level before the blueprint can be
 determined.
 
-.. versionchanged:: 0.11
 
-   Handlers are prioritized by specificity of the exception classes they are
-   registered for instead of the order they are registered in.
+Generic Exception Handlers
+``````````````````````````
+
+It is possible to register error handlers for very generic base classes
+such as ``HTTPException`` or even ``Exception``. However, be aware that
+these will catch more than you might expect.
+
+For example, an error handler for ``HTTPException`` might be useful for turning
+the default HTML errors pages into JSON. However, this
+handler will trigger for things you don't cause directly, such as 404
+and 405 errors during routing. Be sure to craft your handler carefully
+so you don't lose information about the HTTP error.
+
+.. code-block:: python
+
+    from flask import json
+    from werkzeug.exceptions import HTTPException
+
+    @app.errorhandler(HTTPException)
+    def handle_exception(e):
+        """Return JSON instead of HTML for HTTP errors."""
+        # start with the correct headers and status code from the error
+        response = e.get_response()
+        # replace the body with JSON
+        response.data = json.dumps({
+            "code": e.code,
+            "name": e.name,
+            "description": e.description,
+        })
+        response.content_type = "application/json"
+        return response
+
+An error handler for ``Exception`` might seem useful for changing how
+all errors, even unhandled ones, are presented to the user. However,
+this is similar to doing ``except Exception:`` in Python, it will
+capture *all* otherwise unhandled errors, including all HTTP status
+codes.
+
+In most cases it will be safer to register handlers for more
+specific exceptions. Since ``HTTPException`` instances are valid WSGI
+responses, you could also pass them through directly.
+
+.. code-block:: python
+
+    from werkzeug.exceptions import HTTPException
+
+    @app.errorhandler(Exception)
+    def handle_exception(e):
+        # pass through HTTP errors
+        if isinstance(e, HTTPException):
+            return e
+
+        # now you're handling non-HTTP exceptions only
+        return render_template("500_generic.html", e=e), 500
+
+Error handlers still respect the exception class hierarchy. If you
+register handlers for both ``HTTPException`` and ``Exception``, the
+``Exception`` handler will not handle ``HTTPException`` subclasses
+because the ``HTTPException`` handler is more specific.
+
+
+Unhandled Exceptions
+````````````````````
+
+When there is no error handler registered for an exception, a 500
+Internal Server Error will be returned instead. See
+:meth:`flask.Flask.handle_exception` for information about this
+behavior.
+
+If there is an error handler registered for ``InternalServerError``,
+this will be invoked. As of Flask 1.1.0, this error handler will always
+be passed an instance of ``InternalServerError``, not the original
+unhandled error.
+
+The original error is available as ``e.original_exception``.
+
+An error handler for "500 Internal Server Error" will be passed uncaught
+exceptions in addition to explicit 500 errors. In debug mode, a handler
+for "500 Internal Server Error" will not be used. Instead, the
+interactive debugger will be shown.
+
+
+Custom Error Pages
+------------------
+
+Sometimes when building a Flask application, you might want to raise a
+:exc:`~werkzeug.exceptions.HTTPException` to signal to the user that
+something is wrong with the request. Fortunately, Flask comes with a handy
+:func:`~flask.abort` function that aborts a request with a HTTP error from
+werkzeug as desired. It will also provide a plain black and white error page
+for you with a basic description, but nothing fancy.
+
+Depending on the error code it is less or more likely for the user to
+actually see such an error.
+
+Consider the code below, we might have a user profile route, and if the user
+fails to pass a username we can raise a "400 Bad Request". If the user passes a
+username and we can't find it, we raise a "404 Not Found".
+
+.. code-block:: python
+
+    from flask import abort, render_template, request
+
+    # a username needs to be supplied in the query args
+    # a successful request would be like /profile?username=jack
+    @app.route("/profile")
+    def user_profile():
+        username = request.arg.get("username")
+        # if a username isn't supplied in the request, return a 400 bad request
+        if username is None:
+            abort(400)
+
+        user = get_user(username=username)
+        # if a user can't be found by their username, return 404 not found
+        if user is None:
+            abort(404)
+
+        return render_template("profile.html", user=user)
+
+Here is another example implementation for a "404 Page Not Found" exception:
+
+.. code-block:: python
+
+    from flask import render_template
+
+    @app.errorhandler(404)
+    def page_not_found(e):
+        # note that we set the 404 status explicitly
+        return render_template('404.html'), 404
+
+When using :doc:`/patterns/appfactories`:
+
+.. code-block:: python
+
+    from flask import Flask, render_template
+
+    def page_not_found(e):
+      return render_template('404.html'), 404
+
+    def create_app(config_filename):
+        app = Flask(__name__)
+        app.register_error_handler(404, page_not_found)
+        return app
+
+An example template might be this:
+
+.. code-block:: html+jinja
+
+    {% extends "layout.html" %}
+    {% block title %}Page Not Found{% endblock %}
+    {% block body %}
+      <h1>Page Not Found</h1>
+      <p>What you were looking for is just not there.
+      <p><a href="{{ url_for('index') }}">go somewhere nice</a>
+    {% endblock %}
+
+
+Further Examples
+````````````````
+
+The above examples wouldn't actually be an improvement on the default
+exception pages. We can create a custom 500.html template like this:
+
+.. code-block:: html+jinja
+
+    {% extends "layout.html" %}
+    {% block title %}Internal Server Error{% endblock %}
+    {% block body %}
+      <h1>Internal Server Error</h1>
+      <p>Oops... we seem to have made a mistake, sorry!</p>
+      <p><a href="{{ url_for('index') }}">Go somewhere nice instead</a>
+    {% endblock %}
+
+It can be implemented by rendering the template on "500 Internal Server Error":
+
+.. code-block:: python
+
+    from flask import render_template
+
+    @app.errorhandler(500)
+    def internal_server_error(e):
+        # note that we set the 500 status explicitly
+        return render_template('500.html'), 500
+
+When using :doc:`/patterns/appfactories`:
+
+.. code-block:: python
+
+    from flask import Flask, render_template
+
+    def internal_server_error(e):
+      return render_template('500.html'), 500
+
+    def create_app():
+        app = Flask(__name__)
+        app.register_error_handler(500, internal_server_error)
+        return app
+
+When using :doc:`/blueprints`:
+
+.. code-block:: python
+
+    from flask import Blueprint
+
+    blog = Blueprint('blog', __name__)
+
+    # as a decorator
+    @blog.errorhandler(500)
+    def internal_server_error(e):
+        return render_template('500.html'), 500
+
+    # or with register_error_handler
+    blog.register_error_handler(500, internal_server_error)
+
+
+Blueprint Error Handlers
+------------------------
+
+In :doc:`/blueprints`, most error handlers will work as expected.
+However, there is a caveat concerning handlers for 404 and 405
+exceptions. These error handlers are only invoked from an appropriate
+``raise`` statement or a call to ``abort`` in another of the blueprint's
+view functions; they are not invoked by, e.g., an invalid URL access.
+
+This is because the blueprint does not "own" a certain URL space, so
+the application instance has no way of knowing which blueprint error
+handler it should run if given an invalid URL. If you would like to
+execute different handling strategies for these errors based on URL
+prefixes, they may be defined at the application level using the
+``request`` proxy object.
+
+.. code-block:: python
+
+    from flask import jsonify, render_template
+
+    # at the application level
+    # not the blueprint level
+    @app.errorhandler(404)
+    def page_not_found(e):
+        # if a request is in our blog URL space
+        if request.path.startswith('/blog/'):
+            # we return a custom blog 404 page
+            return render_template("blog/404.html"), 404
+        else:
+            # otherwise we return our generic site-wide 404 page
+            return render_template("404.html"), 404
+
+    @app.errorhandler(405)
+    def method_not_allowed(e):
+        # if a request has the wrong method to our API
+        if request.path.startswith('/api/'):
+            # we return a json saying so
+            return jsonify(message="Method Not Allowed"), 405
+        else:
+            # otherwise we return a generic site-wide 405 page
+            return render_template("405.html"), 405
+
+
+Returning API Errors as JSON
+----------------------------
+
+When building APIs in Flask, some developers realise that the built-in
+exceptions are not expressive enough for APIs and that the content type of
+:mimetype:`text/html` they are emitting is not very useful for API consumers.
+
+Using the same techniques as above and :func:`~flask.json.jsonify` we can return JSON
+responses to API errors.  :func:`~flask.abort` is called
+with a ``description`` parameter. The error handler will
+use that as the JSON error message, and set the status code to 404.
+
+.. code-block:: python
+
+    from flask import abort, jsonify
+
+    @app.errorhandler(404)
+    def resource_not_found(e):
+        return jsonify(error=str(e)), 404
+
+    @app.route("/cheese")
+    def get_one_cheese():
+        resource = get_resource()
+
+        if resource is None:
+            abort(404, description="Resource not found")
+
+        return jsonify(resource)
+
+We can also create custom exception classes. For instance, we can
+introduce a new custom exception for an API that can take a proper human readable message,
+a status code for the error and some optional payload to give more context
+for the error.
+
+This is a simple example:
+
+.. code-block:: python
+
+    from flask import jsonify, request
+
+    class InvalidAPIUsage(Exception):
+        status_code = 400
+
+        def __init__(self, message, status_code=None, payload=None):
+            super().__init__()
+            self.message = message
+            if status_code is not None:
+                self.status_code = status_code
+            self.payload = payload
+
+        def to_dict(self):
+            rv = dict(self.payload or ())
+            rv['message'] = self.message
+            return rv
+
+    @app.errorhandler(InvalidAPIUsage)
+    def invalid_api_usage(e):
+        return jsonify(e.to_dict()), e.status_code
+
+    # an API app route for getting user information
+    # a correct request might be /api/user?user_id=420
+    @app.route("/api/user")
+    def user_api(user_id):
+        user_id = request.arg.get("user_id")
+        if not user_id:
+            raise InvalidAPIUsage("No user id provided!")
+
+        user = get_user(user_id=user_id)
+        if not user:
+            raise InvalidAPIUsage("No such user!", status_code=404)
+
+        return jsonify(user.to_dict())
+
+A view can now raise that exception with an error message. Additionally
+some extra payload can be provided as a dictionary through the `payload`
+parameter.
+
 
 Logging
 -------
 
-See :ref:`logging` for information on how to log exceptions, such as by
-emailing them to admins.
+See :doc:`/logging` for information about how to log exceptions, such as
+by emailing them to admins.
 
 
-Debugging Application Errors
-============================
+Debugging
+---------
 
-For production applications, configure your application with logging and
-notifications as described in :ref:`application-errors`.  This section provides
-pointers when debugging deployment configuration and digging deeper with a
-full-featured Python debugger.
-
-
-When in Doubt, Run Manually
----------------------------
-
-Having problems getting your application configured for production?  If you
-have shell access to your host, verify that you can run your application
-manually from the shell in the deployment environment.  Be sure to run under
-the same user account as the configured deployment to troubleshoot permission
-issues.  You can use Flask's builtin development server with `debug=True` on
-your production host, which is helpful in catching configuration issues, but
-**be sure to do this temporarily in a controlled environment.** Do not run in
-production with `debug=True`.
-
-
-.. _working-with-debuggers:
-
-Working with Debuggers
-----------------------
-
-To dig deeper, possibly to trace code execution, Flask provides a debugger out
-of the box (see :ref:`debug-mode`).  If you would like to use another Python
-debugger, note that debuggers interfere with each other.  You have to set some
-options in order to use your favorite debugger:
-
-* ``debug``        - whether to enable debug mode and catch exceptions
-* ``use_debugger`` - whether to use the internal Flask debugger
-* ``use_reloader`` - whether to reload and fork the process on exception
-
-``debug`` must be True (i.e., exceptions must be caught) in order for the other
-two options to have any value.
-
-If you're using Aptana/Eclipse for debugging you'll need to set both
-``use_debugger`` and ``use_reloader`` to False.
-
-A possible useful pattern for configuration is to set the following in your
-config.yaml (change the block as appropriate for your application, of course)::
-
-   FLASK:
-       DEBUG: True
-       DEBUG_WITH_APTANA: True
-
-Then in your application's entry-point (main.py), you could have something like::
-
-   if __name__ == "__main__":
-       # To allow aptana to receive errors, set use_debugger=False
-       app = create_app(config="config.yaml")
-
-       if app.debug: use_debugger = True
-       try:
-           # Disable Flask's debugger if external debugger is requested
-           use_debugger = not(app.config.get('DEBUG_WITH_APTANA'))
-       except:
-           pass
-       app.run(use_debugger=use_debugger, debug=app.debug,
-               use_reloader=use_debugger, host='0.0.0.0')
+See :doc:`/debugging` for information about how to debug errors in
+development and production.

docs/extensiondev.rst

@@ -1,312 +1,277 @@
 Flask Extension Development
 ===========================
 
-Flask, being a microframework, often requires some repetitive steps to get
-a third party library working. Many such extensions are already available
-on `PyPI`_.
+.. currentmodule:: flask
 
-If you want to create your own Flask extension for something that does not
-exist yet, this guide to extension development will help you get your
-extension running in no time and to feel like users would expect your
-extension to behave.
+Extensions are extra packages that add functionality to a Flask
+application. While `PyPI`_ contains many Flask extensions, you may not
+find one that fits your need. If this is the case, you can create your
+own, and publish it for others to use as well.
 
-Anatomy of an Extension
------------------------
+This guide will show how to create a Flask extension, and some of the
+common patterns and requirements involved. Since extensions can do
+anything, this guide won't be able to cover every possibility.
 
-Extensions are all located in a package called ``flask_something``
-where "something" is the name of the library you want to bridge.  So for
-example if you plan to add support for a library named `simplexml` to
-Flask, you would name your extension's package ``flask_simplexml``.
+The best ways to learn about extensions are to look at how other
+extensions you use are written, and discuss with others. Discuss your
+design ideas with others on our `Discord Chat`_ or
+`GitHub Discussions`_.
 
-The name of the actual extension (the human readable name) however would
-be something like "Flask-SimpleXML".  Make sure to include the name
-"Flask" somewhere in that name and that you check the capitalization.
-This is how users can then register dependencies to your extension in
-their :file:`setup.py` files.
-
-But what do extensions look like themselves?  An extension has to ensure
-that it works with multiple Flask application instances at once.  This is
-a requirement because many people will use patterns like the
-:ref:`app-factories` pattern to create their application as needed to aid
-unittests and to support multiple configurations.  Because of that it is
-crucial that your application supports that kind of behavior.
-
-Most importantly the extension must be shipped with a :file:`setup.py` file and
-registered on PyPI.  Also the development checkout link should work so
-that people can easily install the development version into their
-virtualenv without having to download the library by hand.
-
-Flask extensions must be licensed under a BSD, MIT or more liberal license
-in order to be listed in the Flask Extension Registry.  Keep in mind
-that the Flask Extension Registry is a moderated place and libraries will
-be reviewed upfront if they behave as required.
-
-"Hello Flaskext!"
------------------
-
-So let's get started with creating such a Flask extension.  The extension
-we want to create here will provide very basic support for SQLite3.
-
-First we create the following folder structure::
-
-    flask-sqlite3/
-        flask_sqlite3.py
-        LICENSE
-        README
-
-Here's the contents of the most important files:
-
-setup.py
-````````
-
-The next file that is absolutely required is the :file:`setup.py` file which is
-used to install your Flask extension.  The following contents are
-something you can work with::
-
-    """
-    Flask-SQLite3
-    -------------
-
-    This is the description for that library
-    """
-    from setuptools import setup
+The best extensions share common patterns, so that anyone familiar with
+using one extension won't feel completely lost with another. This can
+only work if collaboration happens early.
 
 
-    setup(
-        name='Flask-SQLite3',
-        version='1.0',
-        url='http://example.com/flask-sqlite3/',
-        license='BSD',
-        author='Your Name',
-        author_email='your-email@example.com',
-        description='Very short description',
-        long_description=__doc__,
-        py_modules=['flask_sqlite3'],
-        # if you would be using a package instead use packages instead
-        # of py_modules:
-        # packages=['flask_sqlite3'],
-        zip_safe=False,
-        include_package_data=True,
-        platforms='any',
-        install_requires=[
-            'Flask'
-        ],
-        classifiers=[
-            'Environment :: Web Environment',
-            'Intended Audience :: Developers',
-            'License :: OSI Approved :: BSD License',
-            'Operating System :: OS Independent',
-            'Programming Language :: Python',
-            'Topic :: Internet :: WWW/HTTP :: Dynamic Content',
-            'Topic :: Software Development :: Libraries :: Python Modules'
-        ]
-    )
+Naming
+------
 
-That's a lot of code but you can really just copy/paste that from existing
-extensions and adapt.
+A Flask extension typically has ``flask`` in its name as a prefix or
+suffix. If it wraps another library, it should include the library name
+as well. This makes it easy to search for extensions, and makes their
+purpose clearer.
 
-flask_sqlite3.py
-````````````````
+A general Python packaging recommendation is that the install name from
+the package index and the name used in ``import`` statements should be
+related. The import name is lowercase, with words separated by
+underscores (``_``). The install name is either lower case or title
+case, with words separated by dashes (``-``). If it wraps another
+library, prefer using the same case as that library's name.
 
-Now this is where your extension code goes.  But how exactly should such
-an extension look like?  What are the best practices?  Continue reading
-for some insight.
+Here are some example install and import names:
 
-Initializing Extensions
------------------------
-
-Many extensions will need some kind of initialization step.  For example,
-consider an application that's currently connecting to SQLite like the
-documentation suggests (:ref:`sqlite3`).  So how does the extension
-know the name of the application object?
-
-Quite simple: you pass it to it.
-
-There are two recommended ways for an extension to initialize:
-
-initialization functions:
-
-    If your extension is called `helloworld` you might have a function
-    called ``init_helloworld(app[, extra_args])`` that initializes the
-    extension for that application.  It could attach before / after
-    handlers etc.
-
-classes:
-
-    Classes work mostly like initialization functions but can later be
-    used to further change the behavior.  For an example look at how the
-    `OAuth extension`_ works: there is an `OAuth` object that provides
-    some helper functions like `OAuth.remote_app` to create a reference to
-    a remote application that uses OAuth.
-
-What to use depends on what you have in mind.  For the SQLite 3 extension
-we will use the class-based approach because it will provide users with an
-object that handles opening and closing database connections.
-
-When designing your classes, it's important to make them easily reusable
-at the module level. This means the object itself must not under any
-circumstances store any application specific state and must be shareable
-between different applications.
-
-The Extension Code
-------------------
-
-Here's the contents of the `flask_sqlite3.py` for copy/paste::
-
-    import sqlite3
-    from flask import current_app, _app_ctx_stack
+-   ``Flask-Name`` imported as ``flask_name``
+-   ``flask-name-lower`` imported as ``flask_name_lower``
+-   ``Flask-ComboName`` imported as ``flask_comboname``
+-   ``Name-Flask`` imported as ``name_flask``
 
 
-    class SQLite3(object):
+The Extension Class and Initialization
+--------------------------------------
+
+All extensions will need some entry point that initializes the
+extension with the application. The most common pattern is to create a
+class that represents the extension's configuration and behavior, with
+an ``init_app`` method to apply the extension instance to the given
+application instance.
+
+.. code-block:: python
+
+    class HelloExtension:
         def __init__(self, app=None):
-            self.app = app
             if app is not None:
                 self.init_app(app)
 
         def init_app(self, app):
-            app.config.setdefault('SQLITE3_DATABASE', ':memory:')
-            app.teardown_appcontext(self.teardown)
+            app.before_request(...)
 
-        def connect(self):
-            return sqlite3.connect(current_app.config['SQLITE3_DATABASE'])
+It is important that the app is not stored on the extension, don't do
+``self.app = app``. The only time the extension should have direct
+access to an app is during ``init_app``, otherwise it should use
+:data:`.current_app`.
 
-        def teardown(self, exception):
-            ctx = _app_ctx_stack.top
-            if hasattr(ctx, 'sqlite3_db'):
-                ctx.sqlite3_db.close()
+This allows the extension to support the application factory pattern,
+avoids circular import issues when importing the extension instance
+elsewhere in a user's code, and makes testing with different
+configurations easier.
 
-        @property
-        def connection(self):
-            ctx = _app_ctx_stack.top
-            if ctx is not None:
-                if not hasattr(ctx, 'sqlite3_db'):
-                    ctx.sqlite3_db = self.connect()
-                return ctx.sqlite3_db
+.. code-block:: python
+
+    hello = HelloExtension()
+
+    def create_app():
+        app = Flask(__name__)
+        hello.init_app(app)
+        return app
+
+Above, the ``hello`` extension instance exists independently of the
+application. This means that other modules in a user's project can do
+``from project import hello`` and use the extension in blueprints before
+the app exists.
+
+The :attr:`Flask.extensions` dict can be used to store a reference to
+the extension on the application, or some other state specific to the
+application. Be aware that this is a single namespace, so use a name
+unique to your extension, such as the extension's name without the
+"flask" prefix.
 
 
-So here's what these lines of code do:
+Adding Behavior
+---------------
 
-1.  The ``__init__`` method takes an optional app object and, if supplied, will
-    call ``init_app``.
-2.  The ``init_app`` method exists so that the ``SQLite3`` object can be
-    instantiated without requiring an app object.  This method supports the
-    factory pattern for creating applications.  The ``init_app`` will set the
-    configuration for the database, defaulting to an in memory database if
-    no configuration is supplied.  In addition, the ``init_app`` method attaches
-    the ``teardown`` handler.
-3.  Next, we define a ``connect`` method that opens a database connection.
-4.  Finally, we add a ``connection`` property that on first access opens
-    the database connection and stores it on the context.  This is also
-    the recommended way to handling resources: fetch resources lazily the
-    first time they are used.
+There are many ways that an extension can add behavior. Any setup
+methods that are available on the :class:`Flask` object can be used
+during an extension's ``init_app`` method.
 
-    Note here that we're attaching our database connection to the top
-    application context via ``_app_ctx_stack.top``. Extensions should use
-    the top context for storing their own information with a sufficiently
-    complex name.
+A common pattern is to use :meth:`~Flask.before_request` to initialize
+some data or a connection at the beginning of each request, then
+:meth:`~Flask.teardown_request` to clean it up at the end. This can be
+stored on :data:`.g`, discussed more below.
 
-So why did we decide on a class-based approach here?  Because using our
-extension looks something like this::
+A more lazy approach is to provide a method that initializes and caches
+the data or connection. For example, a ``ext.get_db`` method could
+create a database connection the first time it's called, so that a view
+that doesn't use the database doesn't create a connection.
 
-    from flask import Flask
-    from flask_sqlite3 import SQLite3
+Besides doing something before and after every view, your extension
+might want to add some specific views as well. In this case, you could
+define a :class:`Blueprint`, then call :meth:`~Flask.register_blueprint`
+during ``init_app`` to add the blueprint to the app.
 
-    app = Flask(__name__)
-    app.config.from_pyfile('the-config.cfg')
-    db = SQLite3(app)
 
-You can then use the database from views like this::
+Configuration Techniques
+------------------------
 
-    @app.route('/')
-    def show_all():
-        cur = db.connection.cursor()
-        cur.execute(...)
+There can be multiple levels and sources of configuration for an
+extension. You should consider what parts of your extension fall into
+each one.
 
-Likewise if you are outside of a request you can use the database by
-pushing an app context::
+-   Configuration per application instance, through ``app.config``
+    values. This is configuration that could reasonably change for each
+    deployment of an application. A common example is a URL to an
+    external resource, such as a database. Configuration keys should
+    start with the extension's name so that they don't interfere with
+    other extensions.
+-   Configuration per extension instance, through ``__init__``
+    arguments. This configuration usually affects how the extension
+    is used, such that it wouldn't make sense to change it per
+    deployment.
+-   Configuration per extension instance, through instance attributes
+    and decorator methods. It might be more ergonomic to assign to
+    ``ext.value``, or use a ``@ext.register`` decorator to register a
+    function, after the extension instance has been created.
+-   Global configuration through class attributes. Changing a class
+    attribute like ``Ext.connection_class`` can customize default
+    behavior without making a subclass. This could be combined
+    per-extension configuration to override defaults.
+-   Subclassing and overriding methods and attributes. Making the API of
+    the extension itself something that can be overridden provides a
+    very powerful tool for advanced customization.
 
-    with app.app_context():
-        cur = db.connection.cursor()
-        cur.execute(...)
+The :class:`~flask.Flask` object itself uses all of these techniques.
 
-At the end of the ``with`` block the teardown handles will be executed
-automatically.
+It's up to you to decide what configuration is appropriate for your
+extension, based on what you need and what you want to support.
 
-Additionally, the ``init_app`` method is used to support the factory pattern
-for creating apps::
+Configuration should not be changed after the application setup phase is
+complete and the server begins handling requests. Configuration is
+global, any changes to it are not guaranteed to be visible to other
+workers.
 
-    db = SQLite3()
-    # Then later on.
-    app = create_app('the-config.cfg')
+
+Data During a Request
+---------------------
+
+When writing a Flask application, the :data:`~flask.g` object is used to
+store information during a request. For example the
+:doc:`tutorial <tutorial/database>` stores a connection to a SQLite
+database as ``g.db``. Extensions can also use this, with some care.
+Since ``g`` is a single global namespace, extensions must use unique
+names that won't collide with user data. For example, use the extension
+name as a prefix, or as a namespace.
+
+.. code-block:: python
+
+    # an internal prefix with the extension name
+    g._hello_user_id = 2
+
+    # or an internal prefix as a namespace
+    from types import SimpleNamespace
+    g._hello = SimpleNamespace()
+    g._hello.user_id = 2
+
+The data in ``g`` lasts for an application context. An application context is
+active during a request, CLI command, or ``with app.app_context()`` block. If
+you're storing something that should be closed, use
+:meth:`~flask.Flask.teardown_appcontext` to ensure that it gets closed when the
+app context ends. If it should only be valid during a request, or would not be
+used in the CLI outside a request, use :meth:`~flask.Flask.teardown_request`.
+
+
+Views and Models
+----------------
+
+Your extension views might want to interact with specific models in your
+database, or some other extension or data connected to your application.
+For example, let's consider a ``Flask-SimpleBlog`` extension that works
+with Flask-SQLAlchemy to provide a ``Post`` model and views to write
+and read posts.
+
+The ``Post`` model needs to subclass the Flask-SQLAlchemy ``db.Model``
+object, but that's only available once you've created an instance of
+that extension, not when your extension is defining its views. So how
+can the view code, defined before the model exists, access the model?
+
+One method could be to use :doc:`views`. During ``__init__``, create
+the model, then create the views by passing the model to the view
+class's :meth:`~views.View.as_view` method.
+
+.. code-block:: python
+
+    class PostAPI(MethodView):
+        def __init__(self, model):
+            self.model = model
+
+        def get(self, id):
+            post = self.model.query.get(id)
+            return jsonify(post.to_json())
+
+    class BlogExtension:
+        def __init__(self, db):
+            class Post(db.Model):
+                id = db.Column(primary_key=True)
+                title = db.Column(db.String, nullable=False)
+
+            self.post_model = Post
+
+        def init_app(self, app):
+            api_view = PostAPI.as_view(model=self.post_model)
+
+    db = SQLAlchemy()
+    blog = BlogExtension(db)
     db.init_app(app)
+    blog.init_app(app)
 
-Keep in mind that supporting this factory pattern for creating apps is required
-for approved flask extensions (described below).
+Another technique could be to use an attribute on the extension, such as
+``self.post_model`` from above. Add the extension to ``app.extensions``
+in ``init_app``, then access
+``current_app.extensions["simple_blog"].post_model`` from views.
 
-.. admonition:: Note on ``init_app``
+You may also want to provide base classes so that users can provide
+their own ``Post`` model that conforms to the API your extension
+expects. So they could implement ``class Post(blog.BasePost)``, then
+set it as ``blog.post_model``.
 
-   As you noticed, ``init_app`` does not assign ``app`` to ``self``.  This
-   is intentional!  Class based Flask extensions must only store the
-   application on the object when the application was passed to the
-   constructor.  This tells the extension: I am not interested in using
-   multiple applications.
-
-   When the extension needs to find the current application and it does
-   not have a reference to it, it must either use the
-   :data:`~flask.current_app` context local or change the API in a way
-   that you can pass the application explicitly.
+As you can see, this can get a bit complex. Unfortunately, there's no
+perfect solution here, only different strategies and tradeoffs depending
+on your needs and how much customization you want to offer. Luckily,
+this sort of resource dependency is not a common need for most
+extensions. Remember, if you need help with design, ask on our
+`Discord Chat`_ or `GitHub Discussions`_.
 
 
-Using _app_ctx_stack
---------------------
+Recommended Extension Guidelines
+--------------------------------
 
-In the example above, before every request, a ``sqlite3_db`` variable is
-assigned to ``_app_ctx_stack.top``.  In a view function, this variable is
-accessible using the ``connection`` property of ``SQLite3``.  During the
-teardown of a request, the ``sqlite3_db`` connection is closed.  By using
-this pattern, the *same* connection to the sqlite3 database is accessible
-to anything that needs it for the duration of the request.
-
-
-Learn from Others
------------------
-
-This documentation only touches the bare minimum for extension development.
-If you want to learn more, it's a very good idea to check out existing extensions
-on the `PyPI`_.  If you feel lost there is still the `mailinglist`_ and the
-`Discord server`_ to get some ideas for nice looking APIs.  Especially if you do
-something nobody before you did, it might be a very good idea to get some more
-input.  This not only generates useful feedback on what people might want from
-an extension, but also avoids having multiple developers working in isolation
-on pretty much the same problem.
-
-Remember: good API design is hard, so introduce your project on the
-mailing list, and let other developers give you a helping hand with
-designing the API.
-
-The best Flask extensions are extensions that share common idioms for the
-API.  And this can only work if collaboration happens early.
-
-Approved Extensions
--------------------
-
-Flask previously had the concept of approved extensions. These came with
-some vetting of support and compatibility. While this list became too
-difficult to maintain over time, the guidelines are still relevant to
-all extensions maintained and developed today, as they help the Flask
+Flask previously had the concept of "approved extensions", where the
+Flask maintainers evaluated the quality, support, and compatibility of
+the extensions before listing them. While the list became too difficult
+to maintain over time, the guidelines are still relevant to all
+extensions maintained and developed today, as they help the Flask
 ecosystem remain consistent and compatible.
 
-0.  An approved Flask extension requires a maintainer. In the event an
-    extension author would like to move beyond the project, the project
-    should find a new maintainer and transfer access to the repository,
-    documentation, PyPI, and any other services. If no maintainer
-    is available, give access to the Pallets core team.
-1.  The naming scheme is *Flask-ExtensionName* or *ExtensionName-Flask*.
+1.  An extension requires a maintainer. In the event an extension author
+    would like to move beyond the project, the project should find a new
+    maintainer and transfer access to the repository, documentation,
+    PyPI, and any other services. The `Pallets-Eco`_ organization on
+    GitHub allows for community maintenance with oversight from the
+    Pallets maintainers.
+2.  The naming scheme is *Flask-ExtensionName* or *ExtensionName-Flask*.
     It must provide exactly one package or module named
     ``flask_extension_name``.
-2.  The extension must be BSD or MIT licensed. It must be open source
-    and publicly available.
-3.  The extension's API must have the following characteristics:
+3.  The extension must use an open source license. The Python web
+    ecosystem tends to prefer BSD or MIT. It must be open source and
+    publicly available.
+4.  The extension's API must have the following characteristics:
 
     -   It must support multiple applications running in the same Python
         process. Use ``current_app`` instead of ``self.app``, store
@@ -314,22 +279,27 @@ ecosystem remain consistent and compatible.
     -   It must be possible to use the factory pattern for creating
         applications. Use the ``ext.init_app()`` pattern.
 
-4.  From a clone of the repository, an extension with its dependencies
-    must be installable with ``pip install -e .``.
-5.  It must ship a testing suite that can be invoked with ``tox -e py``
-    or ``pytest``. If not using ``tox``, the test dependencies should be
-    specified in a ``requirements.txt`` file. The tests must be part of
-    the sdist distribution.
-6.  The documentation must use the ``flask`` theme from the
-    `Official Pallets Themes`_. A link to the documentation or project
-    website must be in the PyPI metadata or the readme.
-7.  For maximum compatibility, the extension should support the same
-    versions of Python that Flask supports. 3.6+ is recommended as of
-    2020. Use ``python_requires=">= 3.6"`` in ``setup.py`` to indicate
-    supported versions.
+5.  From a clone of the repository, an extension with its dependencies
+    must be installable in editable mode with ``pip install -e .``.
+6.  It must ship tests that can be invoked with a common tool like
+    ``tox -e py``, ``nox -s test`` or ``pytest``. If not using ``tox``,
+    the test dependencies should be specified in a requirements file.
+    The tests must be part of the sdist distribution.
+7.  A link to the documentation or project website must be in the PyPI
+    metadata or the readme. The documentation should use the Flask theme
+    from the `Official Pallets Themes`_.
+8.  The extension's dependencies should not use upper bounds or assume
+    any particular version scheme, but should use lower bounds to
+    indicate minimum compatibility support. For example,
+    ``sqlalchemy>=1.4``.
+9.  Indicate the versions of Python supported using ``python_requires=">=version"``.
+    Flask and Pallets policy is to support all Python versions that are not
+    within six months of end of life (EOL). See Python's `EOL calendar`_ for
+    timing.
 
 .. _PyPI: https://pypi.org/search/?c=Framework+%3A%3A+Flask
-.. _OAuth extension: https://pythonhosted.org/Flask-OAuth/
-.. _mailinglist: https://mail.python.org/mailman/listinfo/flask
-.. _Discord server: https://discord.gg/t6rrQZH
+.. _Discord Chat: https://discord.gg/pallets
+.. _GitHub Discussions: https://github.com/pallets/flask/discussions
 .. _Official Pallets Themes: https://pypi.org/project/Pallets-Sphinx-Themes/
+.. _Pallets-Eco: https://github.com/pallets-eco
+.. _EOL calendar: https://devguide.python.org/versions/

docs/extensions.rst

@@ -1,5 +1,3 @@
-.. _extensions:
-
 Extensions
 ==========
 
@@ -23,7 +21,7 @@ Consult each extension's documentation for installation, configuration,
 and usage instructions. Generally, extensions pull their own
 configuration from :attr:`app.config <flask.Flask.config>` and are
 passed an application instance during initialization. For example,
-an extension caled "Flask-Foo" might be used like this::
+an extension called "Flask-Foo" might be used like this::
 
     from flask_foo import Foo
 
@@ -41,10 +39,10 @@ an extension caled "Flask-Foo" might be used like this::
 Building Extensions
 -------------------
 
-While the `PyPI <pypi_>`_ contains many Flask extensions, you may
-not find an extension that fits your need. If this is the case, you can
-create your own. Read :doc:`/extensiondev` to develop your own Flask
-extension.
+While `PyPI <pypi_>`_ contains many Flask extensions, you may not find
+an extension that fits your need. If this is the case, you can create
+your own, and publish it for others to use as well. Read
+:doc:`extensiondev` to develop your own Flask extension.
 
 
 .. _pypi: https://pypi.org/search/?c=Framework+%3A%3A+Flask

docs/foreword.rst

@@ -1,57 +0,0 @@
-Foreword
-========
-
-Read this before you get started with Flask.  This hopefully answers some
-questions about the purpose and goals of the project, and when you
-should or should not be using it.
-
-What does "micro" mean?
------------------------
-
-“Micro” does not mean that your whole web application has to fit into a single
-Python file (although it certainly can), nor does it mean that Flask is lacking
-in functionality. The "micro" in microframework means Flask aims to keep the
-core simple but extensible. Flask won't make many decisions for you, such as
-what database to use. Those decisions that it does make, such as what
-templating engine to use, are easy to change.  Everything else is up to you, so
-that Flask can be everything you need and nothing you don't.
-
-By default, Flask does not include a database abstraction layer, form
-validation or anything else where different libraries already exist that can
-handle that. Instead, Flask supports extensions to add such functionality to
-your application as if it was implemented in Flask itself. Numerous extensions
-provide database integration, form validation, upload handling, various open
-authentication technologies, and more. Flask may be "micro", but it's ready for
-production use on a variety of needs.
-
-Configuration and Conventions
------------------------------
-
-Flask has many configuration values, with sensible defaults, and a few
-conventions when getting started.  By convention, templates and static files are
-stored in subdirectories within the application's Python source tree, with the
-names :file:`templates` and :file:`static` respectively. While this can be changed, you
-usually don't have to, especially when getting started.
-
-Growing with Flask
-------------------
-
-Once you have Flask up and running, you'll find a variety of extensions
-available in the community to integrate your project for production. The Flask
-core team reviews extensions and ensures approved extensions do not break with
-future releases.
-
-As your codebase grows, you are free to make the design decisions appropriate
-for your project.  Flask will continue to provide a very simple glue layer to
-the best that Python has to offer.  You can implement advanced patterns in
-SQLAlchemy or another database tool, introduce non-relational data persistence
-as appropriate, and take advantage of framework-agnostic tools built for WSGI,
-the Python web interface.
-
-Flask includes many hooks to customize its behavior. Should you need more
-customization, the Flask class is built for subclassing. If you are interested
-in that, check out the :ref:`becomingbig` chapter.  If you are curious about
-the Flask design principles, head over to the section about :ref:`design`.
-
-Continue to :ref:`installation`, the :ref:`quickstart`, or the
-:ref:`advanced_foreword`.

docs/gevent.rst

@@ -0,0 +1,125 @@
+Async with Gevent
+=================
+
+`Gevent`_ patches Python's standard library to run within special async workers
+called `greenlets`_. Gevent has existed since long before Python's native
+asyncio was available, and Flask has always worked with it.
+
+.. _gevent: https://www.gevent.org
+.. _greenlets: https://greenlet.readthedocs.io
+
+Gevent is a reliable way to handle numerous, long lived, concurrent connections,
+and to achieve similar capabilities to ASGI and asyncio. This works without
+needing to write ``async def`` or ``await`` anywhere, but relies on gevent and
+greenlet's low level manipulation of the Python interpreter.
+
+Deciding whether you should use gevent with Flask, or `Quart`_, or something
+else, is ultimately up to understanding the specific needs of your project.
+
+.. _quart: https://quart.palletsprojects.com
+
+
+Enabling gevent
+---------------
+
+You need to apply gevent's patching as early as possible in your code. This
+enables gevent's underlying event loop and converts many Python internals to run
+inside it. Add the following at the top of your project's module or top
+``__init__.py``:
+
+.. code-block:: python
+
+    import gevent.monkey
+    gevent.monkey.patch_all()
+
+When deploying in production, use :doc:`/deploying/gunicorn` or
+:doc:`/deploying/uwsgi` with a gevent worker, as described on those pages.
+
+To run concurrent tasks within your own code, such as views, use
+|gevent.spawn|_:
+
+.. |gevent.spawn| replace:: ``gevent.spawn()``
+.. _gevent.spawn: https://www.gevent.org/api/gevent.html#gevent.spawn
+
+.. code-block:: python
+
+    @app.post("/send")
+    def send_email():
+        gevent.spawn(email.send, to="example@example.example", text="example")
+        return "Email is being sent."
+
+If you need to access :data:`request` or other Flask context globals within the
+spawned function, decorate the function with :func:`.stream_with_context` or
+:func:`.copy_current_request_context`. Prefer passing the exact data you need
+when spawning the function, rather than using the decorators.
+
+.. note::
+
+    When using gevent, greenlet>=1.0 is required. When using PyPy, PyPy>=7.3.7
+    is required.
+
+
+.. _gevent-asyncio:
+
+Combining with ``async``/``await``
+----------------------------------
+
+Gevent's patching does not interact well with Flask's built-in asyncio support.
+If you want to use Gevent and asyncio in the same app, you'll need to override
+:meth:`flask.Flask.async_to_sync` to run async functions inside gevent.
+
+.. code-block:: python
+
+    import gevent.monkey
+    gevent.monkey.patch_all()
+
+    import asyncio
+    from flask import Flask, request
+
+    loop = asyncio.EventLoop()
+    gevent.spawn(loop.run_forever)
+
+    class GeventFlask(Flask):
+        def async_to_sync(self, func):
+            def run(*args, **kwargs):
+                coro = func(*args, **kwargs)
+                future = asyncio.run_coroutine_threadsafe(coro, loop)
+                return future.result()
+
+            return run
+
+    app = GeventFlask(__name__)
+
+    @app.get("/")
+    async def greet():
+        await asyncio.sleep(1)
+        return f"Hello, {request.args.get("name", "World")}!"
+
+This starts an asyncio event loop in a gevent worker. Async functions are
+scheduled on that event loop. This may still have limitations, and may need to
+be modified further when using other asyncio implementations.
+
+
+libuv
+~~~~~
+
+`libuv`_ is another event loop implementation that `gevent supports`_. There's
+also a project called `uvloop`_ that enables libuv in asyncio. If you want to
+use libuv, use gevent's support, not uvloop. It may be possible to further
+modify the ``async_to_sync`` code from the previous section to work with uvloop,
+but that's not currently known.
+
+.. _libuv: https://libuv.org/
+.. _gevent supports: https://www.gevent.org/loop_impls.html
+.. _uvloop: https://uvloop.readthedocs.io/
+
+To enable gevent's libuv support, add the following at the *very* top of your
+code, before ``gevent.monkey.patch_all()``:
+
+.. code-block:: python
+
+    import gevent
+    gevent.config.loop = "libuv"
+
+    import gevent.monkey
+    gevent.monkey.patch_all()

docs/htmlfaq.rst

@@ -1,207 +0,0 @@
-HTML/XHTML FAQ
-==============
-
-The Flask documentation and example applications are using HTML5.  You
-may notice that in many situations, when end tags are optional they are
-not used, so that the HTML is cleaner and faster to load.  Because there
-is much confusion about HTML and XHTML among developers, this document tries
-to answer some of the major questions.
-
-
-History of XHTML
-----------------
-
-For a while, it appeared that HTML was about to be replaced by XHTML.
-However, barely any websites on the Internet are actual XHTML (which is
-HTML processed using XML rules).  There are a couple of major reasons
-why this is the case.  One of them is Internet Explorer's lack of proper
-XHTML support. The XHTML spec states that XHTML must be served with the MIME
-type :mimetype:`application/xhtml+xml`, but Internet Explorer refuses to read files
-with that MIME type.
-While it is relatively easy to configure Web servers to serve XHTML properly,
-few people do.  This is likely because properly using XHTML can be quite
-painful.
-
-One of the most important causes of pain is XML's draconian (strict and
-ruthless) error handling.  When an XML parsing error is encountered,
-the browser is supposed to show the user an ugly error message, instead
-of attempting to recover from the error and display what it can.  Most of
-the (X)HTML generation on the web is based on non-XML template engines
-(such as Jinja, the one used in Flask) which do not protect you from
-accidentally creating invalid XHTML.  There are XML based template engines,
-such as Kid and the popular Genshi, but they often come with a larger
-runtime overhead and are not as straightforward to use because they have
-to obey XML rules.
-
-The majority of users, however, assumed they were properly using XHTML.
-They wrote an XHTML doctype at the top of the document and self-closed all
-the necessary tags (``<br>`` becomes ``<br/>`` or ``<br></br>`` in XHTML).
-However, even if the document properly validates as XHTML, what really
-determines XHTML/HTML processing in browsers is the MIME type, which as
-said before is often not set properly. So the valid XHTML was being treated
-as invalid HTML.
-
-XHTML also changed the way JavaScript is used. To properly work with XHTML,
-programmers have to use the namespaced DOM interface with the XHTML
-namespace to query for HTML elements.
-
-History of HTML5
-----------------
-
-Development of the HTML5 specification was started in 2004 under the name
-"Web Applications 1.0" by the Web Hypertext Application Technology Working
-Group, or WHATWG (which was formed by the major browser vendors Apple,
-Mozilla, and Opera) with the goal of writing a new and improved HTML
-specification, based on existing browser behavior instead of unrealistic
-and backwards-incompatible specifications.
-
-For example, in HTML4 ``<title/Hello/`` theoretically parses exactly the
-same as ``<title>Hello</title>``.  However, since people were using
-XHTML-like tags along the lines of ``<link />``, browser vendors implemented
-the XHTML syntax over the syntax defined by the specification.
-
-In 2007, the specification was adopted as the basis of a new HTML
-specification under the umbrella of the W3C, known as HTML5.  Currently,
-it appears that XHTML is losing traction, as the XHTML 2 working group has
-been disbanded and HTML5 is being implemented by all major browser vendors.
-
-HTML versus XHTML
------------------
-
-The following table gives you a quick overview of features available in
-HTML 4.01, XHTML 1.1 and HTML5. (XHTML 1.0 is not included, as it was
-superseded by XHTML 1.1 and the barely-used XHTML5.)
-
-.. tabularcolumns:: |p{9cm}|p{2cm}|p{2cm}|p{2cm}|
-
-+-----------------------------------------+----------+----------+----------+
-|                                         | HTML4.01 | XHTML1.1 | HTML5    |
-+=========================================+==========+==========+==========+
-| ``<tag/value/`` == ``<tag>value</tag>`` | |Y| [1]_ | |N|      | |N|      |
-+-----------------------------------------+----------+----------+----------+
-| ``<br/>`` supported                     | |N|      | |Y|      | |Y| [2]_ |
-+-----------------------------------------+----------+----------+----------+
-| ``<script/>`` supported                 | |N|      | |Y|      | |N|      |
-+-----------------------------------------+----------+----------+----------+
-| should be served as `text/html`         | |Y|      | |N| [3]_ | |Y|      |
-+-----------------------------------------+----------+----------+----------+
-| should be served as                     | |N|      | |Y|      | |N|      |
-| `application/xhtml+xml`                 |          |          |          |
-+-----------------------------------------+----------+----------+----------+
-| strict error handling                   | |N|      | |Y|      | |N|      |
-+-----------------------------------------+----------+----------+----------+
-| inline SVG                              | |N|      | |Y|      | |Y|      |
-+-----------------------------------------+----------+----------+----------+
-| inline MathML                           | |N|      | |Y|      | |Y|      |
-+-----------------------------------------+----------+----------+----------+
-| ``<video>`` tag                         | |N|      | |N|      | |Y|      |
-+-----------------------------------------+----------+----------+----------+
-| ``<audio>`` tag                         | |N|      | |N|      | |Y|      |
-+-----------------------------------------+----------+----------+----------+
-| New semantic tags like ``<article>``    | |N|      | |N|      | |Y|      |
-+-----------------------------------------+----------+----------+----------+
-
-.. [1] This is an obscure feature inherited from SGML. It is usually not
-       supported by browsers, for reasons detailed above.
-.. [2] This is for compatibility with server code that generates XHTML for
-       tags such as ``<br>``.  It should not be used in new code.
-.. [3] XHTML 1.0 is the last XHTML standard that allows to be served
-       as `text/html` for backwards compatibility reasons.
-
-.. |Y| image:: _static/yes.png
-       :alt: Yes
-.. |N| image:: _static/no.png
-       :alt: No
-
-What does "strict" mean?
-------------------------
-
-HTML5 has strictly defined parsing rules, but it also specifies exactly
-how a browser should react to parsing errors - unlike XHTML, which simply
-states parsing should abort. Some people are confused by apparently
-invalid syntax that still generates the expected results (for example,
-missing end tags or unquoted attribute values).
-
-Some of these work because of the lenient error handling most browsers use
-when they encounter a markup error, others are actually specified.  The
-following constructs are optional in HTML5 by standard, but have to be
-supported by browsers:
-
--   Wrapping the document in an ``<html>`` tag
--   Wrapping header elements in ``<head>`` or the body elements in
-    ``<body>``
--   Closing the ``<p>``, ``<li>``, ``<dt>``, ``<dd>``, ``<tr>``,
-    ``<td>``, ``<th>``, ``<tbody>``, ``<thead>``, or ``<tfoot>`` tags.
--   Quoting attributes, so long as they contain no whitespace or
-    special characters (like ``<``, ``>``, ``'``, or ``"``).
--   Requiring boolean attributes to have a value.
-
-This means the following page in HTML5 is perfectly valid:
-
-.. sourcecode:: html
-
-    <!doctype html>
-    <title>Hello HTML5</title>
-    <div class=header>
-      <h1>Hello HTML5</h1>
-      <p class=tagline>HTML5 is awesome
-    </div>
-    <ul class=nav>
-      <li><a href=/index>Index</a>
-      <li><a href=/downloads>Downloads</a>
-      <li><a href=/about>About</a>
-    </ul>
-    <div class=body>
-      <h2>HTML5 is probably the future</h2>
-      <p>
-        There might be some other things around but in terms of
-        browser vendor support, HTML5 is hard to beat.
-      <dl>
-        <dt>Key 1
-        <dd>Value 1
-        <dt>Key 2
-        <dd>Value 2
-      </dl>
-    </div>
-
-
-New technologies in HTML5
--------------------------
-
-HTML5 adds many new features that make Web applications easier to write
-and to use.
-
--   The ``<audio>`` and ``<video>`` tags provide a way to embed audio and
-    video without complicated add-ons like QuickTime or Flash.
--   Semantic elements like ``<article>``, ``<header>``, ``<nav>``, and
-    ``<time>`` that make content easier to understand.
--   The ``<canvas>`` tag, which supports a powerful drawing API, reducing
-    the need for server-generated images to present data graphically.
--   New form control types like ``<input type="date">`` that allow user
-    agents to make entering and validating values easier.
--   Advanced JavaScript APIs like Web Storage, Web Workers, Web Sockets,
-    geolocation, and offline applications.
-
-Many other features have been added, as well. A good guide to new features
-in HTML5 is Mark Pilgrim's soon-to-be-published book, `Dive Into HTML5`_.
-Not all of them are supported in browsers yet, however, so use caution.
-
-.. _Dive Into HTML5: https://diveintohtml5.info/
-
-What should be used?
---------------------
-
-Currently, the answer is HTML5.  There are very few reasons to use XHTML
-considering the latest developments in Web browsers.  To summarize the
-reasons given above:
-
--   Internet Explorer (which, sadly, currently leads in market share)
-    has poor support for XHTML.
--   Many JavaScript libraries also do not support XHTML, due to the more
-    complicated namespacing API it requires.
--   HTML5 adds several new features, including semantic tags and the
-    long-awaited ``<audio>`` and ``<video>`` tags.
--   It has the support of most browser vendors behind it.
--   It is much easier to write, and more compact.
-
-For most applications, it is undoubtedly better to use HTML5 than XHTML.

docs/index.rst

@@ -3,60 +3,65 @@
 Welcome to Flask
 ================
 
-.. image:: _static/flask-logo.png
-    :alt: Flask: web development, one drop at a time
+.. image:: _static/flask-name.svg
     :align: center
-    :target: https://palletsprojects.com/p/flask/
+    :height: 200px
 
-Welcome to Flask's documentation. Get started with :ref:`installation`
-and then get an overview with the :ref:`quickstart`. There is also a
-more detailed :ref:`tutorial` that shows how to create a small but
+Welcome to Flask's documentation. Flask is a lightweight WSGI web application framework.
+It is designed to make getting started quick and easy, with the ability to scale up to
+complex applications.
+
+Get started with :doc:`installation`
+and then get an overview with the :doc:`quickstart`. There is also a
+more detailed :doc:`tutorial/index` that shows how to create a small but
 complete application with Flask. Common patterns are described in the
-:ref:`patterns` section. The rest of the docs describe each component of
-Flask in detail, with a full reference in the :ref:`api` section.
+:doc:`patterns/index` section. The rest of the docs describe each
+component of Flask in detail, with a full reference in the :doc:`api`
+section.
 
-Flask depends on the `Jinja`_ template engine and the `Werkzeug`_ WSGI
-toolkit. The documentation for these libraries can be found at:
+Flask depends on the `Werkzeug`_ WSGI toolkit, the `Jinja`_ template engine, and the
+`Click`_ CLI toolkit. Be sure to check their documentation as well as Flask's when
+looking for information.
 
-- `Jinja documentation <http://jinja.pocoo.org/docs>`_
-- `Werkzeug documentation <https://werkzeug.palletsprojects.com/>`_
-
-.. _Jinja: https://www.palletsprojects.com/p/jinja/
-.. _Werkzeug: https://www.palletsprojects.com/p/werkzeug/
+.. _Werkzeug: https://werkzeug.palletsprojects.com
+.. _Jinja: https://jinja.palletsprojects.com
+.. _Click: https://click.palletsprojects.com
 
 
 User's Guide
 ------------
 
-This part of the documentation, which is mostly prose, begins with some
-background information about Flask, then focuses on step-by-step
-instructions for web development with Flask.
+Flask provides configuration and conventions, with sensible defaults, to get started.
+This section of the documentation explains the different parts of the Flask framework
+and how they can be used, customized, and extended. Beyond Flask itself, look for
+community-maintained extensions to add even more functionality.
 
 .. toctree::
    :maxdepth: 2
 
-   foreword
-   advanced_foreword
    installation
    quickstart
    tutorial/index
    templating
    testing
    errorhandling
+   debugging
    logging
    config
    signals
    views
+   lifecycle
    appcontext
-   reqcontext
    blueprints
    extensions
    cli
    server
    shell
    patterns/index
+   web-security
    deploying/index
-   becomingbig
+   gevent
+   async-await
 
 
 API Reference
@@ -74,18 +79,11 @@ method, this part of the documentation is for you.
 Additional Notes
 ----------------
 
-Design notes, legal information and changelog are here for the interested.
-
 .. toctree::
    :maxdepth: 2
 
    design
-   htmlfaq
-   security
-   unicode
    extensiondev
-   styleguide
-   upgrading
-   changelog
-   license
    contributing
+   license
+   changes

docs/installation.rst

@@ -1,13 +1,12 @@
-.. _installation:
-
 Installation
 ============
 
+
 Python Version
 --------------
 
-We recommend using the latest version of Python 3. Flask supports Python 3.4
-and newer, Python 2.7, and PyPy.
+We recommend using the latest version of Python. Flask supports Python 3.10 and newer.
+
 
 Dependencies
 ------------
@@ -24,12 +23,15 @@ These distributions will be installed automatically when installing Flask.
   to protect Flask's session cookie.
 * `Click`_ is a framework for writing command line applications. It provides
   the ``flask`` command and allows adding custom management commands.
+* `Blinker`_ provides support for :doc:`signals`.
 
 .. _Werkzeug: https://palletsprojects.com/p/werkzeug/
 .. _Jinja: https://palletsprojects.com/p/jinja/
 .. _MarkupSafe: https://palletsprojects.com/p/markupsafe/
 .. _ItsDangerous: https://palletsprojects.com/p/itsdangerous/
 .. _Click: https://palletsprojects.com/p/click/
+.. _Blinker: https://blinker.readthedocs.io/
+
 
 Optional dependencies
 ~~~~~~~~~~~~~~~~~~~~~
@@ -37,20 +39,26 @@ Optional dependencies
 These distributions will not be installed automatically. Flask will detect and
 use them if you install them.
 
-* `Blinker`_ provides support for :ref:`signals`.
-* `SimpleJSON`_ is a fast JSON implementation that is compatible with
-  Python's ``json`` module. It is preferred for JSON operations if it is
-  installed.
 * `python-dotenv`_ enables support for :ref:`dotenv` when running ``flask``
   commands.
 * `Watchdog`_ provides a faster, more efficient reloader for the development
   server.
 
-.. _Blinker: https://pythonhosted.org/blinker/
-.. _SimpleJSON: https://simplejson.readthedocs.io/
 .. _python-dotenv: https://github.com/theskumar/python-dotenv#readme
 .. _watchdog: https://pythonhosted.org/watchdog/
 
+
+greenlet
+~~~~~~~~
+
+You may choose to use :doc:`/gevent` with your application. In this case,
+greenlet>=1.0 is required. When using PyPy, PyPy>=7.3.7 is required.
+
+These are not minimum supported versions, they only indicate the first
+versions that added necessary features. You should use the latest
+versions of each.
+
+
 Virtual environments
 --------------------
 
@@ -66,43 +74,35 @@ Virtual environments are independent groups of Python libraries, one for each
 project. Packages installed for one project will not affect other projects or
 the operating system's packages.
 
-Python 3 comes bundled with the :mod:`venv` module to create virtual
-environments. If you're using a modern version of Python, you can continue on
-to the next section.
+Python comes bundled with the :mod:`venv` module to create virtual
+environments.
 
-If you're using Python 2, see :ref:`install-install-virtualenv` first.
 
 .. _install-create-env:
 
 Create an environment
 ~~~~~~~~~~~~~~~~~~~~~
 
-Create a project folder and a :file:`venv` folder within:
+Create a project folder and a :file:`.venv` folder within:
 
-.. code-block:: sh
+.. tabs::
 
-    mkdir myproject
-    cd myproject
-    python3 -m venv venv
+   .. group-tab:: macOS/Linux
 
-On Windows:
+      .. code-block:: text
 
-.. code-block:: bat
+         $ mkdir myproject
+         $ cd myproject
+         $ python3 -m venv .venv
 
-    py -3 -m venv venv
+   .. group-tab:: Windows
 
-If you needed to install virtualenv because you are using Python 2, use
-the following command instead:
+      .. code-block:: text
 
-.. code-block:: sh
+         > mkdir myproject
+         > cd myproject
+         > py -3 -m venv .venv
 
-    python2 -m virtualenv venv
-
-On Windows:
-
-.. code-block:: bat
-
-    \Python27\Scripts\virtualenv.exe venv
 
 .. _install-activate-env:
 
@@ -111,76 +111,33 @@ Activate the environment
 
 Before you work on your project, activate the corresponding environment:
 
-.. code-block:: sh
+.. tabs::
 
-    . venv/bin/activate
+   .. group-tab:: macOS/Linux
 
-On Windows:
+      .. code-block:: text
 
-.. code-block:: bat
+         $ . .venv/bin/activate
 
-    venv\Scripts\activate
+   .. group-tab:: Windows
+
+      .. code-block:: text
+
+         > .venv\Scripts\activate
+
+Your shell prompt will change to show the name of the activated
+environment.
 
-Your shell prompt will change to show the name of the activated environment.
 
 Install Flask
 -------------
 
-Within the activated environment, use the following command to install Flask:
+Within the activated environment, use the following command to install
+Flask:
 
 .. code-block:: sh
 
-    pip install Flask
+    $ pip install Flask
 
 Flask is now installed. Check out the :doc:`/quickstart` or go to the
 :doc:`Documentation Overview </index>`.
-
-Living on the edge
-~~~~~~~~~~~~~~~~~~
-
-If you want to work with the latest Flask code before it's released, install or
-update the code from the master branch:
-
-.. code-block:: sh
-
-    pip install -U https://github.com/pallets/flask/archive/master.tar.gz
-
-.. _install-install-virtualenv:
-
-Install virtualenv
-------------------
-
-If you are using Python 2, the venv module is not available. Instead,
-install `virtualenv`_.
-
-On Linux, virtualenv is provided by your package manager:
-
-.. code-block:: sh
-
-    # Debian, Ubuntu
-    sudo apt-get install python-virtualenv
-
-    # CentOS, Fedora
-    sudo yum install python-virtualenv
-
-    # Arch
-    sudo pacman -S python-virtualenv
-
-If you are on Mac OS X or Windows, download `get-pip.py`_, then:
-
-.. code-block:: sh
-
-    sudo python2 Downloads/get-pip.py
-    sudo python2 -m pip install virtualenv
-
-On Windows, as an administrator:
-
-.. code-block:: bat
-
-    \Python27\python.exe Downloads\get-pip.py
-    \Python27\python.exe -m pip install virtualenv
-
-Now you can return above and :ref:`install-create-env`.
-
-.. _virtualenv: https://virtualenv.pypa.io/
-.. _get-pip.py: https://bootstrap.pypa.io/get-pip.py

docs/license.rst

@@ -1,19 +1,5 @@
-License
-=======
+BSD-3-Clause License
+====================
 
-Source License
---------------
-
-This license applies to all files in the Flask repository and source
-distribution. This includes Flask's source code, the examples, and
-tests, as well as the documentation.
-
-.. include:: ../LICENSE.rst
-
-
-Artwork License
----------------
-
-This license applies to Flask's logo.
-
-.. include:: ../artwork/LICENSE.rst
+.. literalinclude:: ../LICENSE.txt
+    :language: text

docs/lifecycle.rst

@@ -0,0 +1,171 @@
+Application Structure and Lifecycle
+===================================
+
+Flask makes it pretty easy to write a web application. But there are quite a few
+different parts to an application and to each request it handles. Knowing what happens
+during application setup, serving, and handling requests will help you know what's
+possible in Flask and how to structure your application.
+
+
+Application Setup
+-----------------
+
+The first step in creating a Flask application is creating the application object. Each
+Flask application is an instance of the :class:`.Flask` class, which collects all
+configuration, extensions, and views.
+
+.. code-block:: python
+
+    from flask import Flask
+
+    app = Flask(__name__)
+    app.config.from_mapping(
+        SECRET_KEY="dev",
+    )
+    app.config.from_prefixed_env()
+
+    @app.route("/")
+    def index():
+        return "Hello, World!"
+
+This is known as the "application setup phase", it's the code you write that's outside
+any view functions or other handlers. It can be split up between different modules and
+sub-packages, but all code that you want to be part of your application must be imported
+in order for it to be registered.
+
+All application setup must be completed before you start serving your application and
+handling requests. This is because WSGI servers divide work between multiple workers, or
+can be distributed across multiple machines. If the configuration changed in one worker,
+there's no way for Flask to ensure consistency between other workers.
+
+Flask tries to help developers catch some of these setup ordering issues by showing an
+error if setup-related methods are called after requests are handled. In that case
+you'll see this error:
+
+    The setup method 'route' can no longer be called on the application. It has already
+    handled its first request, any changes will not be applied consistently.
+    Make sure all imports, decorators, functions, etc. needed to set up the application
+    are done before running it.
+
+However, it is not possible for Flask to detect all cases of out-of-order setup. In
+general, don't do anything to modify the ``Flask`` app object and ``Blueprint`` objects
+from within view functions that run during requests. This includes:
+
+-   Adding routes, view functions, and other request handlers with ``@app.route``,
+    ``@app.errorhandler``, ``@app.before_request``, etc.
+-   Registering blueprints.
+-   Loading configuration with ``app.config``.
+-   Setting up the Jinja template environment with ``app.jinja_env``.
+-   Setting a session interface, instead of the default itsdangerous cookie.
+-   Setting a JSON provider with ``app.json``, instead of the default provider.
+-   Creating and initializing Flask extensions.
+
+
+Serving the Application
+-----------------------
+
+Flask is a WSGI application framework. The other half of WSGI is the WSGI server. During
+development, Flask, through Werkzeug, provides a development WSGI server with the
+``flask run`` CLI command. When you are done with development, use a production server
+to serve your application, see :doc:`deploying/index`.
+
+Regardless of what server you're using, it will follow the :pep:`3333` WSGI spec. The
+WSGI server will be told how to access your Flask application object, which is the WSGI
+application. Then it will start listening for HTTP requests, translate the request data
+into a WSGI environ, and call the WSGI application with that data. The WSGI application
+will return data that is translated into an HTTP response.
+
+#.  Browser or other client makes HTTP request.
+#.  WSGI server receives request.
+#.  WSGI server converts HTTP data to WSGI ``environ`` dict.
+#.  WSGI server calls WSGI application with the ``environ``.
+#.  Flask, the WSGI application, does all its internal processing to route the request
+    to a view function, handle errors, etc.
+#.  Flask translates View function return into WSGI response data, passes it to WSGI
+    server.
+#.  WSGI server creates and send an HTTP response.
+#.  Client receives the HTTP response.
+
+
+Middleware
+~~~~~~~~~~
+
+The WSGI application above is a callable that behaves in a certain way. Middleware
+is a WSGI application that wraps another WSGI application. It's a similar concept to
+Python decorators. The outermost middleware will be called by the server. It can modify
+the data passed to it, then call the WSGI application (or further middleware) that it
+wraps, and so on. And it can take the return value of that call and modify it further.
+
+From the WSGI server's perspective, there is one WSGI application, the one it calls
+directly. Typically, Flask is the "real" application at the end of the chain of
+middleware. But even Flask can call further WSGI applications, although that's an
+advanced, uncommon use case.
+
+A common middleware you'll see used with Flask is Werkzeug's
+:class:`~werkzeug.middleware.proxy_fix.ProxyFix`, which modifies the request to look
+like it came directly from a client even if it passed through HTTP proxies on the way.
+There are other middleware that can handle serving static files, authentication, etc.
+
+
+How a Request is Handled
+------------------------
+
+For us, the interesting part of the steps above is when Flask gets called by the WSGI
+server (or middleware). At that point, it will do quite a lot to handle the request and
+generate the response. At the most basic, it will match the URL to a view function, call
+the view function, and pass the return value back to the server. But there are many more
+parts that you can use to customize its behavior.
+
+#.  WSGI server calls the Flask object, which calls :meth:`.Flask.wsgi_app`.
+#.  An :class:`.AppContext` object is created. This converts the WSGI ``environ``
+    dict into a :class:`.Request` object.
+#.  The :doc:`app context <appcontext>` is pushed, which makes
+    :data:`.current_app`, :data:`.g`, :data:`.request`, and :data:`.session`
+    available.
+#.  The :data:`.appcontext_pushed` signal is sent.
+#.  The URL is matched against the URL rules registered with the :meth:`~.Flask.route`
+    decorator during application setup. If there is no match, the error - usually a 404,
+    405, or redirect - is stored to be handled later.
+#.  The :data:`.request_started` signal is sent.
+#.  Any :meth:`~.Flask.url_value_preprocessor` decorated functions are called.
+#.  Any :meth:`~.Flask.before_request` decorated functions are called. If any of
+    these function returns a value it is treated as the response immediately.
+#.  If the URL didn't match a route a few steps ago, that error is raised now.
+#.  The :meth:`~.Flask.route` decorated view function associated with the matched URL
+    is called and returns a value to be used as the response.
+#.  If any step so far raised an exception, and there is an :meth:`~.Flask.errorhandler`
+    decorated function that matches the exception class or HTTP error code, it is
+    called to handle the error and return a response.
+#.  Whatever returned a response value - a before request function, the view, or an
+    error handler, that value is converted to a :class:`.Response` object.
+#.  Any :func:`~.after_this_request` decorated functions are called, which can modify
+    the response object. They are then cleared.
+#.  Any :meth:`~.Flask.after_request` decorated functions are called, which can modify
+    the response object.
+#.  The session is saved, persisting any modified session data using the app's
+    :attr:`~.Flask.session_interface`.
+#.  The :data:`.request_finished` signal is sent.
+#.  If any step so far raised an exception, and it was not handled by an error handler
+    function, it is handled now. HTTP exceptions are treated as responses with their
+    corresponding status code, other exceptions are converted to a generic 500 response.
+    The :data:`.got_request_exception` signal is sent.
+#.  The response object's status, headers, and body are returned to the WSGI server.
+#.  Any :meth:`~.Flask.teardown_request` decorated functions are called.
+#.  The :data:`.request_tearing_down` signal is sent.
+#.  Any :meth:`~.Flask.teardown_appcontext` decorated functions are called.
+#.  The :data:`.appcontext_tearing_down` signal is sent.
+#.  The app context is popped, :data:`.current_app`, :data:`.g`, :data:`.request`,
+    and :data:`.session` are no longer available.
+#.  The :data:`.appcontext_popped` signal is sent.
+
+When executing a CLI command or plain app context without request data, the same
+order of steps is followed, omitting the steps that refer to the request.
+
+A :class:`Blueprint` can add handlers for these events that are specific to the
+blueprint. The handlers for a blueprint will run if the blueprint
+owns the route that matches the request.
+
+There are even more decorators and customization points than this, but that aren't part
+of every request lifecycle. They're more specific to certain things you might use during
+a request, such as templates, building URLs, or handling JSON data. See the rest of this
+documentation, as well as the :doc:`api` to explore further.

docs/logging.rst

@@ -1,12 +1,12 @@
-.. _logging:
-
 Logging
 =======
 
-Flask uses standard Python :mod:`logging`. All Flask-related messages are
-logged under the ``'flask'`` logger namespace.
-:meth:`Flask.logger <flask.Flask.logger>` returns the logger named
-``'flask.app'``, and can be used to log messages for your application. ::
+Flask uses standard Python :mod:`logging`. Messages about your Flask
+application are logged with :meth:`app.logger <flask.Flask.logger>`,
+which takes the same name as :attr:`app.name <flask.Flask.name>`. This
+logger can also be used to log your own messages.
+
+.. code-block:: python
 
     @app.route('/login', methods=['POST'])
     def login():
@@ -20,6 +20,9 @@ logged under the ``'flask'`` logger namespace.
             app.logger.info('%s failed to log in', user.username)
             abort(401)
 
+If you don't configure logging, Python's default log level is usually
+'warning'. Nothing below the configured level will be visible.
+
 
 Basic Configuration
 -------------------
@@ -156,7 +159,7 @@ Depending on your project, it may be more useful to configure each logger you
 care about separately, instead of configuring only the root logger. ::
 
     for logger in (
-        app.logger,
+        logging.getLogger(app.name),
         logging.getLogger('sqlalchemy'),
         logging.getLogger('other_package'),
     ):

docs/patterns/apierrors.rst

@@ -1,63 +0,0 @@
-Implementing API Exceptions
-===========================
-
-It's very common to implement RESTful APIs on top of Flask.  One of the
-first things that developers run into is the realization that the builtin
-exceptions are not expressive enough for APIs and that the content type of
-:mimetype:`text/html` they are emitting is not very useful for API consumers.
-
-The better solution than using ``abort`` to signal errors for invalid API
-usage is to implement your own exception type and install an error handler
-for it that produces the errors in the format the user is expecting.
-
-Simple Exception Class
-----------------------
-
-The basic idea is to introduce a new exception that can take a proper
-human readable message, a status code for the error and some optional
-payload to give more context for the error.
-
-This is a simple example::
-
-    from flask import jsonify
-
-    class InvalidUsage(Exception):
-        status_code = 400
-
-        def __init__(self, message, status_code=None, payload=None):
-            Exception.__init__(self)
-            self.message = message
-            if status_code is not None:
-                self.status_code = status_code
-            self.payload = payload
-
-        def to_dict(self):
-            rv = dict(self.payload or ())
-            rv['message'] = self.message
-            return rv
-
-A view can now raise that exception with an error message.  Additionally
-some extra payload can be provided as a dictionary through the `payload`
-parameter.
-
-Registering an Error Handler
-----------------------------
-
-At that point views can raise that error, but it would immediately result
-in an internal server error.  The reason for this is that there is no
-handler registered for this error class.  That however is easy to add::
-
-    @app.errorhandler(InvalidUsage)
-    def handle_invalid_usage(error):
-        response = jsonify(error.to_dict())
-        response.status_code = error.status_code
-        return response
-
-Usage in Views
---------------
-
-Here is how a view can use that functionality::
-
-    @app.route('/foo')
-    def get_foo():
-        raise InvalidUsage('This view is gone', status_code=410)

docs/patterns/appdispatch.rst

@@ -1,5 +1,3 @@
-.. _app-dispatch:
-
 Application Dispatching
 =======================
 
@@ -10,44 +8,30 @@ Django and a Flask application in the same interpreter side by side if
 you want.  The usefulness of this depends on how the applications work
 internally.
 
-The fundamental difference from the :ref:`module approach
-<larger-applications>` is that in this case you are running the same or
-different Flask applications that are entirely isolated from each other.
-They run different configurations and are dispatched on the WSGI level.
+The fundamental difference from :doc:`packages` is that in this case you
+are running the same or different Flask applications that are entirely
+isolated from each other. They run different configurations and are
+dispatched on the WSGI level.
 
 
 Working with this Document
 --------------------------
 
-Each of the techniques and examples below results in an ``application`` object
-that can be run with any WSGI server.  For production, see :ref:`deployment`.
-For development, Werkzeug provides a builtin server for development available
-at :func:`werkzeug.serving.run_simple`::
+Each of the techniques and examples below results in an ``application``
+object that can be run with any WSGI server. For development, use the
+``flask run`` command to start a development server. For production, see
+:doc:`/deploying/index`.
 
-    from werkzeug.serving import run_simple
-    run_simple('localhost', 5000, application, use_reloader=True)
-
-Note that :func:`run_simple <werkzeug.serving.run_simple>` is not intended for
-use in production.  Use a :ref:`full-blown WSGI server <deployment>`.
-
-In order to use the interactive debugger, debugging must be enabled both on
-the application and the simple server. Here is the "hello world" example with
-debugging and :func:`run_simple <werkzeug.serving.run_simple>`::
+.. code-block:: python
 
     from flask import Flask
-    from werkzeug.serving import run_simple
 
     app = Flask(__name__)
-    app.debug = True
 
     @app.route('/')
     def hello_world():
         return 'Hello World!'
 
-    if __name__ == '__main__':
-        run_simple('localhost', 5000, app,
-                   use_reloader=True, use_debugger=True, use_evalex=True)
-
 
 Combining Applications
 ----------------------
@@ -60,7 +44,9 @@ are combined by the dispatcher middleware into a larger one that is
 dispatched based on prefix.
 
 For example you could have your main application run on ``/`` and your
-backend interface on ``/backend``::
+backend interface on ``/backend``.
+
+.. code-block:: python
 
     from werkzeug.middleware.dispatcher import DispatcherMiddleware
     from frontend_app import application as frontend
@@ -79,7 +65,7 @@ with different configurations.  Assuming the application is created inside
 a function and you can call that function to instantiate it, that is
 really easy to implement.  In order to develop your application to support
 creating new instances in functions have a look at the
-:ref:`app-factories` pattern.
+:doc:`appfactories` pattern.
 
 A very common example would be creating applications per subdomain.  For
 instance you configure your webserver to dispatch all requests for all
@@ -91,11 +77,13 @@ the dynamic application creation.
 The perfect level for abstraction in that regard is the WSGI layer.  You
 write your own WSGI application that looks at the request that comes and
 delegates it to your Flask application.  If that application does not
-exist yet, it is dynamically created and remembered::
+exist yet, it is dynamically created and remembered.
+
+.. code-block:: python
 
     from threading import Lock
 
-    class SubdomainDispatcher(object):
+    class SubdomainDispatcher:
 
         def __init__(self, domain, create_app):
             self.domain = domain
@@ -119,7 +107,9 @@ exist yet, it is dynamically created and remembered::
             return app(environ, start_response)
 
 
-This dispatcher can then be used like this::
+This dispatcher can then be used like this:
+
+.. code-block:: python
 
     from myapplication import create_app, get_user_for_subdomain
     from werkzeug.exceptions import NotFound
@@ -145,12 +135,14 @@ Dispatch by Path
 
 Dispatching by a path on the URL is very similar.  Instead of looking at
 the ``Host`` header to figure out the subdomain one simply looks at the
-request path up to the first slash::
+request path up to the first slash.
+
+.. code-block:: python
 
     from threading import Lock
-    from werkzeug.wsgi import pop_path_info, peek_path_info
+    from wsgiref.util import shift_path_info
 
-    class PathDispatcher(object):
+    class PathDispatcher:
 
         def __init__(self, default_app, create_app):
             self.default_app = default_app
@@ -168,15 +160,24 @@ request path up to the first slash::
                 return app
 
         def __call__(self, environ, start_response):
-            app = self.get_application(peek_path_info(environ))
+            app = self.get_application(_peek_path_info(environ))
             if app is not None:
-                pop_path_info(environ)
+                shift_path_info(environ)
             else:
                 app = self.default_app
             return app(environ, start_response)
 
+    def _peek_path_info(environ):
+        segments = environ.get("PATH_INFO", "").lstrip("/").split("/", 1)
+        if segments:
+            return segments[0]
+
+        return None
+
 The big difference between this and the subdomain one is that this one
-falls back to another application if the creator function returns ``None``::
+falls back to another application if the creator function returns ``None``.
+
+.. code-block:: python
 
     from myapplication import create_app, default_app, get_user_for_prefix
 

docs/patterns/appfactories.rst

@@ -1,10 +1,8 @@
-.. _app-factories:
-
 Application Factories
 =====================
 
 If you are already using packages and blueprints for your application
-(:ref:`blueprints`) there are a couple of really nice ways to further improve
+(:doc:`/blueprints`) there are a couple of really nice ways to further improve
 the experience.  A common pattern is creating the application object when
 the blueprint is imported.  But if you move the creation of this object
 into a function, you can then create multiple instances of this app later.
@@ -89,19 +87,22 @@ For more information about the design of extensions refer to :doc:`/extensiondev
 Using Applications
 ------------------
 
-To run such an application, you can use the :command:`flask` command::
+To run such an application, you can use the :command:`flask` command:
 
-    export FLASK_APP=myapp
-    flask run
+.. code-block:: text
 
-Flask will automatically detect the factory (``create_app`` or ``make_app``)
-in ``myapp``. You can also pass arguments to the factory like this::
+    $ flask --app hello run
 
-    export FLASK_APP="myapp:create_app('dev')"
-    flask run
+Flask will automatically detect the factory if it is named
+``create_app`` or ``make_app`` in ``hello``. You can also pass arguments
+to the factory like this:
 
-Then the ``create_app`` factory in ``myapp`` is called with the string
-``'dev'`` as the argument. See :doc:`/cli` for more detail.
+.. code-block:: text
+
+    $ flask --app 'hello:create_app(local_auth=True)' run
+
+Then the ``create_app`` factory in ``hello`` is called with the keyword
+argument ``local_auth=True``. See :doc:`/cli` for more detail.
 
 Factory Improvements
 --------------------

docs/patterns/caching.rst

@@ -1,5 +1,3 @@
-.. _caching-pattern:
-
 Caching
 =======
 
@@ -11,7 +9,7 @@ you actually put the result of that calculation into a cache for some
 time.
 
 Flask itself does not provide caching for you, but `Flask-Caching`_, an
-extentions for Flask does. Flask-Caching supports various backends, and it is
+extension for Flask does. Flask-Caching supports various backends, and it is
 even possible to develop your own caching backend.
 
 

docs/patterns/celery.rst

@@ -1,101 +1,242 @@
-Celery Background Tasks
-=======================
+Background Tasks with Celery
+============================
 
-If your application has a long running task, such as processing some uploaded
-data or sending email, you don't want to wait for it to finish during a
-request. Instead, use a task queue to send the necessary data to another
-process that will run the task in the background while the request returns
-immediately.
+If your application has a long running task, such as processing some uploaded data or
+sending email, you don't want to wait for it to finish during a request. Instead, use a
+task queue to send the necessary data to another process that will run the task in the
+background while the request returns immediately.
+
+`Celery`_ is a powerful task queue that can be used for simple background tasks as well
+as complex multi-stage programs and schedules. This guide will show you how to configure
+Celery using Flask. Read Celery's `First Steps with Celery`_ guide to learn how to use
+Celery itself.
+
+.. _Celery: https://celery.readthedocs.io
+.. _First Steps with Celery: https://celery.readthedocs.io/en/latest/getting-started/first-steps-with-celery.html
+
+The Flask repository contains `an example <https://github.com/pallets/flask/tree/main/examples/celery>`_
+based on the information on this page, which also shows how to use JavaScript to submit
+tasks and poll for progress and results.
 
-Celery is a powerful task queue that can be used for simple background tasks
-as well as complex multi-stage programs and schedules. This guide will show you
-how to configure Celery using Flask, but assumes you've already read the
-`First Steps with Celery <http://docs.celeryproject.org/en/latest/getting-started/first-steps-with-celery.html>`_
-guide in the Celery documentation.
 
 Install
 -------
 
-Celery is a separate Python package. Install it from PyPI using pip::
+Install Celery from PyPI, for example using pip:
+
+.. code-block:: text
 
     $ pip install celery
 
-Configure
----------
 
-The first thing you need is a Celery instance, this is called the celery
-application.  It serves the same purpose as the :class:`~flask.Flask`
-object in Flask, just for Celery.  Since this instance is used as the
-entry-point for everything you want to do in Celery, like creating tasks
-and managing workers, it must be possible for other modules to import it.
+Integrate Celery with Flask
+---------------------------
 
-For instance you can place this in a ``tasks`` module.  While you can use
-Celery without any reconfiguration with Flask, it becomes a bit nicer by
-subclassing tasks and adding support for Flask's application contexts and
-hooking it up with the Flask configuration.
+You can use Celery without any integration with Flask, but it's convenient to configure
+it through Flask's config, and to let tasks access the Flask application.
 
-This is all that is necessary to properly integrate Celery with Flask::
+Celery uses similar ideas to Flask, with a ``Celery`` app object that has configuration
+and registers tasks. While creating a Flask app, use the following code to create and
+configure a Celery app as well.
 
-    from celery import Celery
+.. code-block:: python
 
-    def make_celery(app):
-        celery = Celery(
-            app.import_name,
-            backend=app.config['CELERY_RESULT_BACKEND'],
-            broker=app.config['CELERY_BROKER_URL']
-        )
-        celery.conf.update(app.config)
+    from celery import Celery, Task
 
-        class ContextTask(celery.Task):
-            def __call__(self, *args, **kwargs):
+    def celery_init_app(app: Flask) -> Celery:
+        class FlaskTask(Task):
+            def __call__(self, *args: object, **kwargs: object) -> object:
                 with app.app_context():
                     return self.run(*args, **kwargs)
 
-        celery.Task = ContextTask
-        return celery
+        celery_app = Celery(app.name, task_cls=FlaskTask)
+        celery_app.config_from_object(app.config["CELERY"])
+        celery_app.set_default()
+        app.extensions["celery"] = celery_app
+        return celery_app
 
-The function creates a new Celery object, configures it with the broker
-from the application config, updates the rest of the Celery config from
-the Flask config and then creates a subclass of the task that wraps the
-task execution in an application context.
+This creates and returns a ``Celery`` app object. Celery `configuration`_ is taken from
+the ``CELERY`` key in the Flask configuration. The Celery app is set as the default, so
+that it is seen during each request. The ``Task`` subclass automatically runs task
+functions with a Flask app context active, so that services like your database
+connections are available.
 
-An example task
----------------
+.. _configuration: https://celery.readthedocs.io/en/stable/userguide/configuration.html
 
-Let's write a task that adds two numbers together and returns the result. We
-configure Celery's broker and backend to use Redis, create a ``celery``
-application using the factor from above, and then use it to define the task. ::
+Here's a basic ``example.py`` that configures Celery to use Redis for communication. We
+enable a result backend, but ignore results by default. This allows us to store results
+only for tasks where we care about the result.
+
+.. code-block:: python
 
     from flask import Flask
 
-    flask_app = Flask(__name__)
-    flask_app.config.update(
-        CELERY_BROKER_URL='redis://localhost:6379',
-        CELERY_RESULT_BACKEND='redis://localhost:6379'
+    app = Flask(__name__)
+    app.config.from_mapping(
+        CELERY=dict(
+            broker_url="redis://localhost",
+            result_backend="redis://localhost",
+            task_ignore_result=True,
+        ),
     )
-    celery = make_celery(flask_app)
+    celery_app = celery_init_app(app)
 
-    @celery.task()
-    def add_together(a, b):
+Point the ``celery worker`` command at this and it will find the ``celery_app`` object.
+
+.. code-block:: text
+
+    $ celery -A example worker --loglevel INFO
+
+You can also run the ``celery beat`` command to run tasks on a schedule. See Celery's
+docs for more information about defining schedules.
+
+.. code-block:: text
+
+    $ celery -A example beat --loglevel INFO
+
+
+Application Factory
+-------------------
+
+When using the Flask application factory pattern, call the ``celery_init_app`` function
+inside the factory. It sets ``app.extensions["celery"]`` to the Celery app object, which
+can be used to get the Celery app from the Flask app returned by the factory.
+
+.. code-block:: python
+
+    def create_app() -> Flask:
+        app = Flask(__name__)
+        app.config.from_mapping(
+            CELERY=dict(
+                broker_url="redis://localhost",
+                result_backend="redis://localhost",
+                task_ignore_result=True,
+            ),
+        )
+        app.config.from_prefixed_env()
+        celery_init_app(app)
+        return app
+
+To use ``celery`` commands, Celery needs an app object, but that's no longer directly
+available. Create a ``make_celery.py`` file that calls the Flask app factory and gets
+the Celery app from the returned Flask app.
+
+.. code-block:: python
+
+    from example import create_app
+
+    flask_app = create_app()
+    celery_app = flask_app.extensions["celery"]
+
+Point the ``celery`` command to this file.
+
+.. code-block:: text
+
+    $ celery -A make_celery worker --loglevel INFO
+    $ celery -A make_celery beat --loglevel INFO
+
+
+Defining Tasks
+--------------
+
+Using ``@celery_app.task`` to decorate task functions requires access to the
+``celery_app`` object, which won't be available when using the factory pattern. It also
+means that the decorated tasks are tied to the specific Flask and Celery app instances,
+which could be an issue during testing if you change configuration for a test.
+
+Instead, use Celery's ``@shared_task`` decorator. This creates task objects that will
+access whatever the "current app" is, which is a similar concept to Flask's blueprints
+and app context. This is why we called ``celery_app.set_default()`` above.
+
+Here's an example task that adds two numbers together and returns the result.
+
+.. code-block:: python
+
+    from celery import shared_task
+
+    @shared_task(ignore_result=False)
+    def add_together(a: int, b: int) -> int:
         return a + b
 
-This task can now be called in the background::
+Earlier, we configured Celery to ignore task results by default. Since we want to know
+the return value of this task, we set ``ignore_result=False``. On the other hand, a task
+that didn't need a result, such as sending an email, wouldn't set this.
 
-    result = add_together.delay(23, 42)
-    result.wait()  # 65
 
-Run a worker
-------------
+Calling Tasks
+-------------
 
-If you jumped in and already executed the above code you will be
-disappointed to learn that ``.wait()`` will never actually return.
-That's because you also need to run a Celery worker to receive and execute the
-task. ::
+The decorated function becomes a task object with methods to call it in the background.
+The simplest way is to use the ``delay(*args, **kwargs)`` method. See Celery's docs for
+more methods.
 
-    $ celery -A your_application.celery worker
+A Celery worker must be running to run the task. Starting a worker is shown in the
+previous sections.
 
-The ``your_application`` string has to point to your application's package
-or module that creates the ``celery`` object.
+.. code-block:: python
 
-Now that the worker is running, ``wait`` will return the result once the task
-is finished.
+    from flask import request
+
+    @app.post("/add")
+    def start_add() -> dict[str, object]:
+        a = request.form.get("a", type=int)
+        b = request.form.get("b", type=int)
+        result = add_together.delay(a, b)
+        return {"result_id": result.id}
+
+The route doesn't get the task's result immediately. That would defeat the purpose by
+blocking the response. Instead, we return the running task's result id, which we can use
+later to get the result.
+
+
+Getting Results
+---------------
+
+To fetch the result of the task we started above, we'll add another route that takes the
+result id we returned before. We return whether the task is finished (ready), whether it
+finished successfully, and what the return value (or error) was if it is finished.
+
+.. code-block:: python
+
+    from celery.result import AsyncResult
+
+    @app.get("/result/<id>")
+    def task_result(id: str) -> dict[str, object]:
+        result = AsyncResult(id)
+        return {
+            "ready": result.ready(),
+            "successful": result.successful(),
+            "value": result.result if result.ready() else None,
+        }
+
+Now you can start the task using the first route, then poll for the result using the
+second route. This keeps the Flask request workers from being blocked waiting for tasks
+to finish.
+
+The Flask repository contains `an example <https://github.com/pallets/flask/tree/main/examples/celery>`_
+using JavaScript to submit tasks and poll for progress and results.
+
+
+Passing Data to Tasks
+---------------------
+
+The "add" task above took two integers as arguments. To pass arguments to tasks, Celery
+has to serialize them to a format that it can pass to other processes. Therefore,
+passing complex objects is not recommended. For example, it would be impossible to pass
+a SQLAlchemy model object, since that object is probably not serializable and is tied to
+the session that queried it.
+
+Pass the minimal amount of data necessary to fetch or recreate any complex data within
+the task. Consider a task that will run when the logged in user asks for an archive of
+their data. The Flask request knows the logged in user, and has the user object queried
+from the database. It got that by querying the database for a given id, so the task can
+do the same thing. Pass the user's id rather than the user object.
+
+.. code-block:: python
+
+    @shared_task
+    def generate_user_archive(user_id: str) -> None:
+        user = db.session.get(User, user_id)
+        ...
+
+    generate_user_archive.delay(current_user.id)

docs/patterns/deferredcallbacks.rst

@@ -1,5 +1,3 @@
-.. _deferred-callbacks:
-
 Deferred Request Callbacks
 ==========================
 
@@ -16,7 +14,7 @@ response object.
 
 One way is to avoid the situation. Very often that is possible. For instance
 you can try to move that logic into a :meth:`~flask.Flask.after_request`
-callback instead. However, sometimes moving code there makes it more
+callback instead. However, sometimes moving code there makes it
 more complicated or awkward to reason about.
 
 As an alternative, you can use :func:`~flask.after_this_request` to register

docs/patterns/distribute.rst

@@ -1,177 +0,0 @@
-.. _distribute-deployment:
-
-Deploying with Setuptools
-=========================
-
-`Setuptools`_, is an extension library that is commonly used to
-distribute Python libraries and extensions. It extends distutils, a basic
-module installation system shipped with Python to also support various more
-complex constructs that make larger applications easier to distribute:
-
-- **support for dependencies**: a library or application can declare a
-  list of other libraries it depends on which will be installed
-  automatically for you.
-- **package registry**: setuptools registers your package with your
-  Python installation.  This makes it possible to query information
-  provided by one package from another package.  The best known feature of
-  this system is the entry point support which allows one package to
-  declare an "entry point" that another package can hook into to extend the
-  other package.
-- **installation manager**: :command:`pip` can install other libraries for you.
-
-If you have Python 2 (>=2.7.9) or Python 3 (>=3.4) installed from python.org,
-you will already have pip and setuptools on your system.  Otherwise, you
-will need to install them yourself.
-
-Flask itself, and all the libraries you can find on PyPI are distributed with
-either setuptools or distutils.
-
-In this case we assume your application is called
-:file:`yourapplication.py` and you are not using a module, but a :ref:`package
-<larger-applications>`. If you have not yet converted your application into
-a package, head over to the :ref:`larger-applications` pattern to see
-how this can be done.
-
-A working deployment with setuptools is the first step into more complex
-and more automated deployment scenarios.  If you want to fully automate
-the process, also read the :ref:`fabric-deployment` chapter.
-
-Basic Setup Script
-------------------
-
-Because you have Flask installed, you have setuptools available on your system.
-Flask already depends upon setuptools.
-
-Standard disclaimer applies: :ref:`you better use a virtualenv
-<virtualenv>`.
-
-Your setup code always goes into a file named :file:`setup.py` next to your
-application.  The name of the file is only convention, but because
-everybody will look for a file with that name, you better not change it.
-
-A basic :file:`setup.py` file for a Flask application looks like this::
-
-    from setuptools import setup
-
-    setup(
-        name='Your Application',
-        version='1.0',
-        long_description=__doc__,
-        packages=['yourapplication'],
-        include_package_data=True,
-        zip_safe=False,
-        install_requires=['Flask']
-    )
-
-Please keep in mind that you have to list subpackages explicitly.  If you
-want setuptools to lookup the packages for you automatically, you can use
-the ``find_packages`` function::
-
-    from setuptools import setup, find_packages
-
-    setup(
-        ...
-        packages=find_packages()
-    )
-
-Most parameters to the ``setup`` function should be self explanatory,
-``include_package_data`` and ``zip_safe`` might not be.
-``include_package_data`` tells setuptools to look for a :file:`MANIFEST.in` file
-and install all the entries that match as package data.  We will use this
-to distribute the static files and templates along with the Python module
-(see :ref:`distributing-resources`).  The ``zip_safe`` flag can be used to
-force or prevent zip Archive creation.  In general you probably don't want
-your packages to be installed as zip files because some tools do not
-support them and they make debugging a lot harder.
-
-
-Tagging Builds
---------------
-
-It is useful to distinguish between release and development builds. Add a
-:file:`setup.cfg` file to configure these options. ::
-
-    [egg_info]
-    tag_build = .dev
-    tag_date = 1
-
-    [aliases]
-    release = egg_info -Db ''
-
-Running ``python setup.py sdist`` will create a development package
-with ".dev" and the current date appended: ``flaskr-1.0.dev20160314.tar.gz``.
-Running ``python setup.py release sdist`` will create a release package
-with only the version: ``flaskr-1.0.tar.gz``.
-
-
-.. _distributing-resources:
-
-Distributing Resources
-----------------------
-
-If you try to install the package you just created, you will notice that
-folders like :file:`static` or :file:`templates` are not installed for you.  The
-reason for this is that setuptools does not know which files to add for
-you.  What you should do, is to create a :file:`MANIFEST.in` file next to your
-:file:`setup.py` file.  This file lists all the files that should be added to
-your tarball::
-
-    recursive-include yourapplication/templates *
-    recursive-include yourapplication/static *
-
-Don't forget that even if you enlist them in your :file:`MANIFEST.in` file, they
-won't be installed for you unless you set the `include_package_data`
-parameter of the ``setup`` function to ``True``!
-
-
-Declaring Dependencies
-----------------------
-
-Dependencies are declared in the ``install_requires`` parameter as a list.
-Each item in that list is the name of a package that should be pulled from
-PyPI on installation.  By default it will always use the most recent
-version, but you can also provide minimum and maximum version
-requirements.  Here some examples::
-
-    install_requires=[
-        'Flask>=0.2',
-        'SQLAlchemy>=0.6',
-        'BrokenPackage>=0.7,<=1.0'
-    ]
-
-As mentioned earlier, dependencies are pulled from PyPI.  What if you
-want to depend on a package that cannot be found on PyPI and won't be
-because it is an internal package you don't want to share with anyone?
-Just do it as if there was a PyPI entry and provide a list of
-alternative locations where setuptools should look for tarballs::
-
-    dependency_links=['http://example.com/yourfiles']
-
-Make sure that page has a directory listing and the links on the page are
-pointing to the actual tarballs with their correct filenames as this is
-how setuptools will find the files.  If you have an internal company
-server that contains the packages, provide the URL to that server.
-
-
-Installing / Developing
------------------------
-
-To install your application (ideally into a virtualenv) just run the
-:file:`setup.py` script with the ``install`` parameter.  It will install your
-application into the virtualenv's site-packages folder and also download
-and install all dependencies::
-
-    $ python setup.py install
-
-If you are developing on the package and also want the requirements to be
-installed, you can use the ``develop`` command instead::
-
-    $ python setup.py develop
-
-This has the advantage of just installing a link to the site-packages
-folder instead of copying the data over.  You can then continue to work on
-the code without having to run ``install`` again after each change.
-
-
-.. _pip: https://pypi.org/project/pip/
-.. _Setuptools: https://pypi.org/project/setuptools/

docs/patterns/errorpages.rst

@@ -1,125 +0,0 @@
-.. _errorpages:
-
-Custom Error Pages
-==================
-
-Flask comes with a handy :func:`~flask.abort` function that aborts a
-request with an HTTP error code early.  It will also provide a plain black
-and white error page for you with a basic description, but nothing fancy.
-
-Depending on the error code it is less or more likely for the user to
-actually see such an error.
-
-Common Error Codes
-------------------
-
-The following error codes are some that are often displayed to the user,
-even if the application behaves correctly:
-
-*404 Not Found*
-    The good old "chap, you made a mistake typing that URL" message.  So
-    common that even novices to the internet know that 404 means: damn,
-    the thing I was looking for is not there.  It's a very good idea to
-    make sure there is actually something useful on a 404 page, at least a
-    link back to the index.
-
-*403 Forbidden*
-    If you have some kind of access control on your website, you will have
-    to send a 403 code for disallowed resources.  So make sure the user
-    is not lost when they try to access a forbidden resource.
-
-*410 Gone*
-    Did you know that there the "404 Not Found" has a brother named "410
-    Gone"?  Few people actually implement that, but the idea is that
-    resources that previously existed and got deleted answer with 410
-    instead of 404.  If you are not deleting documents permanently from
-    the database but just mark them as deleted, do the user a favour and
-    use the 410 code instead and display a message that what they were
-    looking for was deleted for all eternity.
-
-*500 Internal Server Error*
-    Usually happens on programming errors or if the server is overloaded.
-    A terribly good idea is to have a nice page there, because your
-    application *will* fail sooner or later (see also:
-    :ref:`application-errors`).
-
-
-Error Handlers
---------------
-
-An error handler is a function that returns a response when a type of error is
-raised, similar to how a view is a function that returns a response when a
-request URL is matched. It is passed the instance of the error being handled,
-which is most likely a :exc:`~werkzeug.exceptions.HTTPException`. An error
-handler for "500 Internal Server Error" will be passed uncaught exceptions in
-addition to explicit 500 errors.
-
-An error handler is registered with the :meth:`~flask.Flask.errorhandler`
-decorator or the :meth:`~flask.Flask.register_error_handler` method. A handler
-can be registered for a status code, like 404, or for an exception class.
-
-The status code of the response will not be set to the handler's code. Make
-sure to provide the appropriate HTTP status code when returning a response from
-a handler.
-
-A handler for "500 Internal Server Error" will not be used when running in
-debug mode. Instead, the interactive debugger will be shown.
-
-Here is an example implementation for a "404 Page Not Found" exception::
-
-    from flask import render_template
-
-    @app.errorhandler(404)
-    def page_not_found(e):
-        # note that we set the 404 status explicitly
-        return render_template('404.html'), 404
-
-When using the :ref:`application factory pattern <app-factories>`::
-
-    from flask import Flask, render_template
-
-    def page_not_found(e):
-      return render_template('404.html'), 404
-
-    def create_app(config_filename):
-        app = Flask(__name__)
-        app.register_error_handler(404, page_not_found)
-        return app
-
-An example template might be this:
-
-.. sourcecode:: html+jinja
-
-    {% extends "layout.html" %}
-    {% block title %}Page Not Found{% endblock %}
-    {% block body %}
-      <h1>Page Not Found</h1>
-      <p>What you were looking for is just not there.
-      <p><a href="{{ url_for('index') }}">go somewhere nice</a>
-    {% endblock %}
-
-
-Returning API errors as JSON
-----------------------------
-
-When using Flask for web APIs, you can use the same techniques as above
-to return JSON responses to API errors.  :func:`~flask.abort` is called
-with a ``description`` parameter. The :meth:`~flask.errorhandler` will
-use that as the JSON error message, and set the status code to 404.
-
-.. code-block:: python
-
-    from flask import abort, jsonify
-
-    @app.errorhandler(404)
-    def resource_not_found(e):
-        return jsonify(error=str(e)), 404
-
-    @app.route("/cheese")
-    def get_one_cheese():
-        resource = get_resource()
-
-        if resource is None:
-            abort(404, description="Resource not found")
-
-        return jsonify(resource)

docs/patterns/fabric.rst

@@ -1,186 +0,0 @@
-.. _fabric-deployment:
-
-Deploying with Fabric
-=====================
-
-`Fabric`_ is a tool for Python similar to Makefiles but with the ability
-to execute commands on a remote server.  In combination with a properly
-set up Python package (:ref:`larger-applications`) and a good concept for
-configurations (:ref:`config`) it is very easy to deploy Flask
-applications to external servers.
-
-Before we get started, here a quick checklist of things we have to ensure
-upfront:
-
--   Fabric 1.0 has to be installed locally.  This tutorial assumes the
-    latest version of Fabric.
--   The application already has to be a package and requires a working
-    :file:`setup.py` file (:ref:`distribute-deployment`).
--   In the following example we are using `mod_wsgi` for the remote
-    servers.  You can of course use your own favourite server there, but
-    for this example we chose Apache + `mod_wsgi` because it's very easy
-    to setup and has a simple way to reload applications without root
-    access.
-
-Creating the first Fabfile
---------------------------
-
-A fabfile is what controls what Fabric executes.  It is named :file:`fabfile.py`
-and executed by the `fab` command.  All the functions defined in that file
-will show up as `fab` subcommands.  They are executed on one or more
-hosts.  These hosts can be defined either in the fabfile or on the command
-line.  In this case we will add them to the fabfile.
-
-This is a basic first example that has the ability to upload the current
-source code to the server and install it into a pre-existing
-virtual environment::
-
-    from fabric.api import *
-
-    # the user to use for the remote commands
-    env.user = 'appuser'
-    # the servers where the commands are executed
-    env.hosts = ['server1.example.com', 'server2.example.com']
-
-    def pack():
-        # build the package
-        local('python setup.py sdist --formats=gztar', capture=False)
-
-    def deploy():
-        # figure out the package name and version
-        dist = local('python setup.py --fullname', capture=True).strip()
-        filename = '%s.tar.gz' % dist
-
-        # upload the package to the temporary folder on the server
-        put('dist/%s' % filename, '/tmp/%s' % filename)
-
-        # install the package in the application's virtualenv with pip
-        run('/var/www/yourapplication/env/bin/pip install /tmp/%s' % filename)
-
-        # remove the uploaded package
-        run('rm -r /tmp/%s' % filename)
-
-        # touch the .wsgi file to trigger a reload in mod_wsgi
-        run('touch /var/www/yourapplication.wsgi')
-
-Running Fabfiles
-----------------
-
-Now how do you execute that fabfile?  You use the `fab` command.  To
-deploy the current version of the code on the remote server you would use
-this command::
-
-    $ fab pack deploy
-
-However this requires that our server already has the
-:file:`/var/www/yourapplication` folder created and
-:file:`/var/www/yourapplication/env` to be a virtual environment.  Furthermore
-are we not creating the configuration or ``.wsgi`` file on the server.  So
-how do we bootstrap a new server into our infrastructure?
-
-This now depends on the number of servers we want to set up.  If we just
-have one application server (which the majority of applications will
-have), creating a command in the fabfile for this is overkill.  But
-obviously you can do that.  In that case you would probably call it
-`setup` or `bootstrap` and then pass the servername explicitly on the
-command line::
-
-    $ fab -H newserver.example.com bootstrap
-
-To setup a new server you would roughly do these steps:
-
-1.  Create the directory structure in :file:`/var/www`::
-
-        $ mkdir /var/www/yourapplication
-        $ cd /var/www/yourapplication
-        $ virtualenv --distribute env
-
-2.  Upload a new :file:`application.wsgi` file to the server and the
-    configuration file for the application (eg: :file:`application.cfg`)
-
-3.  Create a new Apache config for ``yourapplication`` and activate it.
-    Make sure to activate watching for changes of the ``.wsgi`` file so
-    that we can automatically reload the application by touching it.
-    (See :ref:`mod_wsgi-deployment` for more information)
-
-So now the question is, where do the :file:`application.wsgi` and
-:file:`application.cfg` files come from?
-
-The WSGI File
--------------
-
-The WSGI file has to import the application and also to set an environment
-variable so that the application knows where to look for the config.  This
-is a short example that does exactly that::
-
-    import os
-    os.environ['YOURAPPLICATION_CONFIG'] = '/var/www/yourapplication/application.cfg'
-    from yourapplication import app
-
-The application itself then has to initialize itself like this to look for
-the config at that environment variable::
-
-    app = Flask(__name__)
-    app.config.from_object('yourapplication.default_config')
-    app.config.from_envvar('YOURAPPLICATION_CONFIG')
-
-This approach is explained in detail in the :ref:`config` section of the
-documentation.
-
-The Configuration File
-----------------------
-
-Now as mentioned above, the application will find the correct
-configuration file by looking up the ``YOURAPPLICATION_CONFIG`` environment
-variable.  So we have to put the configuration in a place where the
-application will able to find it.  Configuration files have the unfriendly
-quality of being different on all computers, so you do not version them
-usually.
-
-A popular approach is to store configuration files for different servers
-in a separate version control repository and check them out on all
-servers.  Then symlink the file that is active for the server into the
-location where it's expected (eg: :file:`/var/www/yourapplication`).
-
-Either way, in our case here we only expect one or two servers and we can
-upload them ahead of time by hand.
-
-
-First Deployment
-----------------
-
-Now we can do our first deployment.  We have set up the servers so that
-they have their virtual environments and activated apache configs.  Now we
-can pack up the application and deploy it::
-
-    $ fab pack deploy
-
-Fabric will now connect to all servers and run the commands as written
-down in the fabfile.  First it will execute pack so that we have our
-tarball ready and then it will execute deploy and upload the source code
-to all servers and install it there.  Thanks to the :file:`setup.py` file we
-will automatically pull in the required libraries into our virtual
-environment.
-
-Next Steps
-----------
-
-From that point onwards there is so much that can be done to make
-deployment actually fun:
-
--   Create a `bootstrap` command that initializes new servers.  It could
-    initialize a new virtual environment, setup apache appropriately etc.
--   Put configuration files into a separate version control repository
-    and symlink the active configs into place.
--   You could also put your application code into a repository and check
-    out the latest version on the server and then install.  That way you
-    can also easily go back to older versions.
--   hook in testing functionality so that you can deploy to an external
-    server and run the test suite.
-
-Working with Fabric is fun and you will notice that it's quite magical to
-type ``fab deploy`` and see your application being deployed automatically
-to one or more remote servers.
-
-
-.. _Fabric: http://www.fabfile.org/

docs/patterns/favicon.rst

@@ -24,8 +24,11 @@ the root path of the domain you either need to configure the web server to
 serve the icon at the root or if you can't do that you're out of luck. If
 however your application is the root you can simply route a redirect::
 
-    app.add_url_rule('/favicon.ico',
-                     redirect_to=url_for('static', filename='favicon.ico'))
+    app.add_url_rule(
+        "/favicon.ico",
+        endpoint="favicon",
+        redirect_to=url_for("static", filename="favicon.ico"),
+    )
 
 If you want to save the extra redirect request you can also write a view
 using :func:`~flask.send_from_directory`::

docs/patterns/fileuploads.rst

@@ -1,5 +1,3 @@
-.. _uploading-files:
-
 Uploading Files
 ===============
 
@@ -25,7 +23,7 @@ bootstrapping code for our application::
     from werkzeug.utils import secure_filename
 
     UPLOAD_FOLDER = '/path/to/the/uploads'
-    ALLOWED_EXTENSIONS = set(['txt', 'pdf', 'png', 'jpg', 'jpeg', 'gif'])
+    ALLOWED_EXTENSIONS = {'txt', 'pdf', 'png', 'jpg', 'jpeg', 'gif'}
 
     app = Flask(__name__)
     app.config['UPLOAD_FOLDER'] = UPLOAD_FOLDER
@@ -39,7 +37,7 @@ Why do we limit the extensions that are allowed?  You probably don't want
 your users to be able to upload everything there if the server is directly
 sending out the data to the client.  That way you can make sure that users
 are not able to upload HTML files that would cause XSS problems (see
-:ref:`xss`).  Also make sure to disallow ``.php`` files if the server
+:ref:`security-xss`).  Also make sure to disallow ``.php`` files if the server
 executes them, but who has PHP installed on their server, right?  :)
 
 Next the functions that check if an extension is valid and that uploads
@@ -57,16 +55,15 @@ the file and redirects the user to the URL for the uploaded file::
                 flash('No file part')
                 return redirect(request.url)
             file = request.files['file']
-            # if user does not select file, browser also
-            # submit an empty part without filename
+            # If the user does not select a file, the browser submits an
+            # empty file without a filename.
             if file.filename == '':
                 flash('No selected file')
                 return redirect(request.url)
             if file and allowed_file(file.filename):
                 filename = secure_filename(file.filename)
                 file.save(os.path.join(app.config['UPLOAD_FOLDER'], filename))
-                return redirect(url_for('uploaded_file',
-                                        filename=filename))
+                return redirect(url_for('download_file', name=filename))
         return '''
         <!doctype html>
         <title>Upload new File</title>
@@ -104,31 +101,28 @@ before storing it directly on the filesystem.
    >>> secure_filename('../../../../home/username/.bashrc')
    'home_username_.bashrc'
 
-Now one last thing is missing: the serving of the uploaded files. In the
-:func:`upload_file()` we redirect the user to
-``url_for('uploaded_file', filename=filename)``, that is, ``/uploads/filename``.
-So we write the :func:`uploaded_file` function to return the file of that name. As
-of Flask 0.5 we can use a function that does that for us::
+We want to be able to serve the uploaded files so they can be downloaded
+by users. We'll define a ``download_file`` view to serve files in the
+upload folder by name. ``url_for("download_file", name=name)`` generates
+download URLs.
+
+.. code-block:: python
 
     from flask import send_from_directory
 
-    @app.route('/uploads/<filename>')
-    def uploaded_file(filename):
-        return send_from_directory(app.config['UPLOAD_FOLDER'],
-                                   filename)
+    @app.route('/uploads/<name>')
+    def download_file(name):
+        return send_from_directory(app.config["UPLOAD_FOLDER"], name)
 
-Alternatively you can register `uploaded_file` as `build_only` rule and
-use the :class:`~werkzeug.wsgi.SharedDataMiddleware`.  This also works with
-older versions of Flask::
+If you're using middleware or the HTTP server to serve files, you can
+register the ``download_file`` endpoint as ``build_only`` so ``url_for``
+will work without a view function.
 
-    from werkzeug.middleware.shared_data import SharedDataMiddleware
-    app.add_url_rule('/uploads/<filename>', 'uploaded_file',
-                     build_only=True)
-    app.wsgi_app = SharedDataMiddleware(app.wsgi_app, {
-        '/uploads':  app.config['UPLOAD_FOLDER']
-    })
+.. code-block:: python
 
-If you now run the application everything should work as expected.
+    app.add_url_rule(
+        "/uploads/<name>", endpoint="download_file", build_only=True
+    )
 
 
 Improving Uploads
@@ -137,17 +131,17 @@ Improving Uploads
 .. versionadded:: 0.6
 
 So how exactly does Flask handle uploads?  Well it will store them in the
-webserver's memory if the files are reasonable small otherwise in a
+webserver's memory if the files are reasonably small, otherwise in a
 temporary location (as returned by :func:`tempfile.gettempdir`).  But how
 do you specify the maximum file size after which an upload is aborted?  By
-default Flask will happily accept file uploads to an unlimited amount of
+default Flask will happily accept file uploads with an unlimited amount of
 memory, but you can limit that by setting the ``MAX_CONTENT_LENGTH``
 config key::
 
     from flask import Flask, Request
 
     app = Flask(__name__)
-    app.config['MAX_CONTENT_LENGTH'] = 16 * 1024 * 1024
+    app.config['MAX_CONTENT_LENGTH'] = 16 * 1000 * 1000
 
 The code above will limit the maximum allowed payload to 16 megabytes.
 If a larger file is transmitted, Flask will raise a
@@ -169,10 +163,9 @@ Upload Progress Bars
 
 A while ago many developers had the idea to read the incoming file in
 small chunks and store the upload progress in the database to be able to
-poll the progress with JavaScript from the client.  Long story short: the
-client asks the server every 5 seconds how much it has transmitted
-already.  Do you realize the irony?  The client is asking for something it
-should already know.
+poll the progress with JavaScript from the client. The client asks the
+server every 5 seconds how much it has transmitted, but this is
+something it should already know.
 
 An Easier Solution
 ------------------
@@ -182,9 +175,8 @@ are JavaScript libraries like jQuery_ that have form plugins to ease the
 construction of progress bar.
 
 Because the common pattern for file uploads exists almost unchanged in all
-applications dealing with uploads, there is also a Flask extension called
-`Flask-Uploads`_ that implements a full fledged upload mechanism with white and
-blacklisting of extensions and more.
+applications dealing with uploads, there are also some Flask extensions that
+implement a full fledged upload mechanism that allows controlling which
+file extensions are allowed to be uploaded.
 
 .. _jQuery: https://jquery.com/
-.. _Flask-Uploads: https://pythonhosted.org/Flask-Uploads/

docs/patterns/flashing.rst

@@ -1,5 +1,3 @@
-.. _message-flashing-pattern:
-
 Message Flashing
 ================
 
@@ -103,7 +101,7 @@ error messages could be displayed with a red background.
 To flash a message with a different category, just use the second argument
 to the :func:`~flask.flash` function::
 
-    flash(u'Invalid password provided', 'error')
+    flash('Invalid password provided', 'error')
 
 Inside the template you then have to tell the
 :func:`~flask.get_flashed_messages` function to also return the

docs/patterns/index.rst

@@ -1,5 +1,3 @@
-.. _patterns:
-
 Patterns for Flask
 ==================
 
@@ -20,10 +18,7 @@ collected in the following pages.
    packages
    appfactories
    appdispatch
-   apierrors
    urlprocessors
-   distribute
-   fabric
    sqlite3
    sqlalchemy
    fileuploads
@@ -32,8 +27,7 @@ collected in the following pages.
    wtforms
    templateinheritance
    flashing
-   jquery
-   errorpages
+   javascript
    lazyloading
    mongoengine
    favicon
@@ -43,3 +37,4 @@ collected in the following pages.
    requestchecksum
    celery
    subclassing
+   singlepageapplications

docs/patterns/javascript.rst

@@ -0,0 +1,261 @@
+JavaScript, ``fetch``, and JSON
+===============================
+
+You may want to make your HTML page dynamic, by changing data without
+reloading the entire page. Instead of submitting an HTML ``<form>`` and
+performing a redirect to re-render the template, you can add
+`JavaScript`_ that calls |fetch|_ and replaces content on the page.
+
+|fetch|_ is the modern, built-in JavaScript solution to making
+requests from a page. You may have heard of other "AJAX" methods and
+libraries, such as |XHR|_ or `jQuery`_. These are no longer needed in
+modern browsers, although you may choose to use them or another library
+depending on your application's requirements. These docs will only focus
+on built-in JavaScript features.
+
+.. _JavaScript: https://developer.mozilla.org/Web/JavaScript
+.. |fetch| replace:: ``fetch()``
+.. _fetch: https://developer.mozilla.org/Web/API/Fetch_API
+.. |XHR| replace:: ``XMLHttpRequest()``
+.. _XHR: https://developer.mozilla.org/Web/API/XMLHttpRequest
+.. _jQuery: https://jquery.com/
+
+
+Rendering Templates
+-------------------
+
+It is important to understand the difference between templates and
+JavaScript. Templates are rendered on the server, before the response is
+sent to the user's browser. JavaScript runs in the user's browser, after
+the template is rendered and sent. Therefore, it is impossible to use
+JavaScript to affect how the Jinja template is rendered, but it is
+possible to render data into the JavaScript that will run.
+
+To provide data to JavaScript when rendering the template, use the
+:func:`~jinja-filters.tojson` filter in a ``<script>`` block. This will
+convert the data to a valid JavaScript object, and ensure that any
+unsafe HTML characters are rendered safely. If you do not use the
+``tojson`` filter, you will get a ``SyntaxError`` in the browser
+console.
+
+.. code-block:: python
+
+    data = generate_report()
+    return render_template("report.html", chart_data=data)
+
+.. code-block:: jinja
+
+    <script>
+        const chart_data = {{ chart_data|tojson }}
+        chartLib.makeChart(chart_data)
+    </script>
+
+A less common pattern is to add the data to a ``data-`` attribute on an
+HTML tag. In this case, you must use single quotes around the value, not
+double quotes, otherwise you will produce invalid or unsafe HTML.
+
+.. code-block:: jinja
+
+    <div data-chart='{{ chart_data|tojson }}'></div>
+
+
+Generating URLs
+---------------
+
+The other way to get data from the server to JavaScript is to make a
+request for it. First, you need to know the URL to request.
+
+The simplest way to generate URLs is to continue to use
+:func:`~flask.url_for` when rendering the template. For example:
+
+.. code-block:: javascript
+
+    const user_url = {{ url_for("user", id=current_user.id)|tojson }}
+    fetch(user_url).then(...)
+
+However, you might need to generate a URL based on information you only
+know in JavaScript. As discussed above, JavaScript runs in the user's
+browser, not as part of the template rendering, so you can't use
+``url_for`` at that point.
+
+In this case, you need to know the "root URL" under which your
+application is served. In simple setups, this is ``/``, but it might
+also be something else, like ``https://example.com/myapp/``.
+
+A simple way to tell your JavaScript code about this root is to set it
+as a global variable when rendering the template. Then you can use it
+when generating URLs from JavaScript.
+
+.. code-block:: javascript
+
+    const SCRIPT_ROOT = {{ request.script_root|tojson }}
+    let user_id = ...  // do something to get a user id from the page
+    let user_url = `${SCRIPT_ROOT}/user/${user_id}`
+    fetch(user_url).then(...)
+
+
+Making a Request with ``fetch``
+-------------------------------
+
+|fetch|_ takes two arguments, a URL and an object with other options,
+and returns a |Promise|_. We won't cover all the available options, and
+will only use ``then()`` on the promise, not other callbacks or
+``await`` syntax. Read the linked MDN docs for more information about
+those features.
+
+By default, the GET method is used. If the response contains JSON, it
+can be used with a ``then()`` callback chain.
+
+.. code-block:: javascript
+
+    const room_url = {{ url_for("room_detail", id=room.id)|tojson }}
+    fetch(room_url)
+        .then(response => response.json())
+        .then(data => {
+            // data is a parsed JSON object
+        })
+
+To send data, use a data method such as POST, and pass the ``body``
+option. The most common types for data are form data or JSON data.
+
+To send form data, pass a populated |FormData|_ object. This uses the
+same format as an HTML form, and would be accessed with ``request.form``
+in a Flask view.
+
+.. code-block:: javascript
+
+    let data = new FormData()
+    data.append("name", "Flask Room")
+    data.append("description", "Talk about Flask here.")
+    fetch(room_url, {
+        "method": "POST",
+        "body": data,
+    }).then(...)
+
+In general, prefer sending request data as form data, as would be used
+when submitting an HTML form. JSON can represent more complex data, but
+unless you need that it's better to stick with the simpler format. When
+sending JSON data, the ``Content-Type: application/json`` header must be
+sent as well, otherwise Flask will return a 415 Unsupported Media Type
+error.
+
+.. code-block:: javascript
+
+    let data = {
+        "name": "Flask Room",
+        "description": "Talk about Flask here.",
+    }
+    fetch(room_url, {
+        "method": "POST",
+        "headers": {"Content-Type": "application/json"},
+        "body": JSON.stringify(data),
+    }).then(...)
+
+.. |Promise| replace:: ``Promise``
+.. _Promise: https://developer.mozilla.org/Web/JavaScript/Reference/Global_Objects/Promise
+.. |FormData| replace:: ``FormData``
+.. _FormData: https://developer.mozilla.org/en-US/docs/Web/API/FormData
+
+
+Following Redirects
+-------------------
+
+A response might be a redirect, for example if you logged in with
+JavaScript instead of a traditional HTML form, and your view returned
+a redirect instead of JSON. JavaScript requests do follow redirects, but
+they don't change the page. If you want to make the page change you can
+inspect the response and apply the redirect manually.
+
+.. code-block:: javascript
+
+    fetch("/login", {"body": ...}).then(
+        response => {
+            if (response.redirected) {
+                window.location = response.url
+            } else {
+                showLoginError()
+            }
+        }
+    )
+
+
+Replacing Content
+-----------------
+
+A response might be new HTML, either a new section of the page to add or
+replace, or an entirely new page. In general, if you're returning the
+entire page, it would be better to handle that with a redirect as shown
+in the previous section. The following example shows how to replace a
+``<div>`` with the HTML returned by a request.
+
+.. code-block:: html
+
+    <div id="geology-fact">
+        {{ include "geology_fact.html" }}
+    </div>
+    <script>
+        const geology_url = {{ url_for("geology_fact")|tojson }}
+        const geology_div = getElementById("geology-fact")
+        fetch(geology_url)
+            .then(response => response.text)
+            .then(text => geology_div.innerHTML = text)
+    </script>
+
+
+Return JSON from Views
+----------------------
+
+To return a JSON object from your API view, you can directly return a
+dict from the view. It will be serialized to JSON automatically.
+
+.. code-block:: python
+
+    @app.route("/user/<int:id>")
+    def user_detail(id):
+        user = User.query.get_or_404(id)
+        return {
+            "username": User.username,
+            "email": User.email,
+            "picture": url_for("static", filename=f"users/{id}/profile.png"),
+        }
+
+If you want to return another JSON type, use the
+:func:`~flask.json.jsonify` function, which creates a response object
+with the given data serialized to JSON.
+
+.. code-block:: python
+
+    from flask import jsonify
+
+    @app.route("/users")
+    def user_list():
+        users = User.query.order_by(User.name).all()
+        return jsonify([u.to_json() for u in users])
+
+It is usually not a good idea to return file data in a JSON response.
+JSON cannot represent binary data directly, so it must be base64
+encoded, which can be slow, takes more bandwidth to send, and is not as
+easy to cache. Instead, serve files using one view, and generate a URL
+to the desired file to include in the JSON. Then the client can make a
+separate request to get the linked resource after getting the JSON.
+
+
+Receiving JSON in Views
+-----------------------
+
+Use the :attr:`~flask.Request.json` property of the
+:data:`~flask.request` object to decode the request's body as JSON. If
+the body is not valid JSON, a 400 Bad Request error will be raised. If
+the ``Content-Type`` header is not set to ``application/json``, a 415
+Unsupported Media Type error will be raised.
+
+.. code-block:: python
+
+    from flask import request
+
+    @app.post("/user/<int:id>")
+    def user_update(id):
+        user = User.query.get_or_404(id)
+        user.update_from_json(request.json)
+        db.session.commit()
+        return user.to_json()

docs/patterns/jquery.rst

@@ -1,167 +1,6 @@
+:orphan:
+
 AJAX with jQuery
 ================
 
-`jQuery`_ is a small JavaScript library commonly used to simplify working
-with the DOM and JavaScript in general.  It is the perfect tool to make
-web applications more dynamic by exchanging JSON between server and
-client.
-
-JSON itself is a very lightweight transport format, very similar to how
-Python primitives (numbers, strings, dicts and lists) look like which is
-widely supported and very easy to parse.  It became popular a few years
-ago and quickly replaced XML as transport format in web applications.
-
-.. _jQuery: https://jquery.com/
-
-Loading jQuery
---------------
-
-In order to use jQuery, you have to download it first and place it in the
-static folder of your application and then ensure it's loaded.  Ideally
-you have a layout template that is used for all pages where you just have
-to add a script statement to the bottom of your ``<body>`` to load jQuery:
-
-.. sourcecode:: html
-
-   <script type=text/javascript src="{{
-     url_for('static', filename='jquery.js') }}"></script>
-
-Another method is using Google's `AJAX Libraries API
-<https://developers.google.com/speed/libraries/>`_ to load jQuery:
-
-.. sourcecode:: html
-
-    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
-    <script>window.jQuery || document.write('<script src="{{
-      url_for('static', filename='jquery.js') }}">\x3C/script>')</script>
-
-In this case you have to put jQuery into your static folder as a fallback, but it will
-first try to load it directly from Google. This has the advantage that your
-website will probably load faster for users if they went to at least one
-other website before using the same jQuery version from Google because it
-will already be in the browser cache.
-
-Where is My Site?
------------------
-
-Do you know where your application is?  If you are developing the answer
-is quite simple: it's on localhost port something and directly on the root
-of that server.  But what if you later decide to move your application to
-a different location?  For example to ``http://example.com/myapp``?  On
-the server side this never was a problem because we were using the handy
-:func:`~flask.url_for` function that could answer that question for
-us, but if we are using jQuery we should not hardcode the path to
-the application but make that dynamic, so how can we do that?
-
-A simple method would be to add a script tag to our page that sets a
-global variable to the prefix to the root of the application.  Something
-like this:
-
-.. sourcecode:: html+jinja
-
-   <script type=text/javascript>
-     $SCRIPT_ROOT = {{ request.script_root|tojson|safe }};
-   </script>
-
-The ``|safe`` is necessary in Flask before 0.10 so that Jinja does not
-escape the JSON encoded string with HTML rules.  Usually this would be
-necessary, but we are inside a ``script`` block here where different rules
-apply.
-
-.. admonition:: Information for Pros
-
-   In HTML the ``script`` tag is declared ``CDATA`` which means that entities
-   will not be parsed.  Everything until ``</script>`` is handled as script.
-   This also means that there must never be any ``</`` between the script
-   tags.  ``|tojson`` is kind enough to do the right thing here and
-   escape slashes for you (``{{ "</script>"|tojson|safe }}`` is rendered as
-   ``"<\/script>"``).
-
-   In Flask 0.10 it goes a step further and escapes all HTML tags with
-   unicode escapes.  This makes it possible for Flask to automatically
-   mark the result as HTML safe.
-
-
-JSON View Functions
--------------------
-
-Now let's create a server side function that accepts two URL arguments of
-numbers which should be added together and then sent back to the
-application in a JSON object.  This is a really ridiculous example and is
-something you usually would do on the client side alone, but a simple
-example that shows how you would use jQuery and Flask nonetheless::
-
-    from flask import Flask, jsonify, render_template, request
-    app = Flask(__name__)
-
-    @app.route('/_add_numbers')
-    def add_numbers():
-        a = request.args.get('a', 0, type=int)
-        b = request.args.get('b', 0, type=int)
-        return jsonify(result=a + b)
-
-    @app.route('/')
-    def index():
-        return render_template('index.html')
-
-As you can see I also added an `index` method here that renders a
-template.  This template will load jQuery as above and have a little form where
-we can add two numbers and a link to trigger the function on the server
-side.
-
-Note that we are using the :meth:`~werkzeug.datastructures.MultiDict.get` method here
-which will never fail.  If the key is missing a default value (here ``0``)
-is returned.  Furthermore it can convert values to a specific type (like
-in our case `int`).  This is especially handy for code that is
-triggered by a script (APIs, JavaScript etc.) because you don't need
-special error reporting in that case.
-
-The HTML
---------
-
-Your index.html template either has to extend a :file:`layout.html` template with
-jQuery loaded and the `$SCRIPT_ROOT` variable set, or do that on the top.
-Here's the HTML code needed for our little application (:file:`index.html`).
-Notice that we also drop the script directly into the HTML here.  It is
-usually a better idea to have that in a separate script file:
-
-.. sourcecode:: html
-
-    <script type=text/javascript>
-      $(function() {
-        $('a#calculate').bind('click', function() {
-          $.getJSON($SCRIPT_ROOT + '/_add_numbers', {
-            a: $('input[name="a"]').val(),
-            b: $('input[name="b"]').val()
-          }, function(data) {
-            $("#result").text(data.result);
-          });
-          return false;
-        });
-      });
-    </script>
-    <h1>jQuery Example</h1>
-    <p><input type=text size=5 name=a> +
-       <input type=text size=5 name=b> =
-       <span id=result>?</span>
-    <p><a href=# id=calculate>calculate server side</a>
-
-I won't go into detail here about how jQuery works, just a very quick
-explanation of the little bit of code above:
-
-1. ``$(function() { ... })`` specifies code that should run once the
-   browser is done loading the basic parts of the page.
-2. ``$('selector')`` selects an element and lets you operate on it.
-3. ``element.bind('event', func)`` specifies a function that should run
-   when the user clicked on the element.  If that function returns
-   `false`, the default behavior will not kick in (in this case, navigate
-   to the `#` URL).
-4. ``$.getJSON(url, data, func)`` sends a ``GET`` request to `url` and will
-   send the contents of the `data` object as query parameters.  Once the
-   data arrived, it will call the given function with the return value as
-   argument.  Note that we can use the `$SCRIPT_ROOT` variable here that
-   we set earlier.
-
-Check out the :gh:`example source <examples/javascript>` for a full
-application demonstrating the code on this page, as well as the same
-thing using ``XMLHttpRequest`` and ``fetch``.
+Obsolete, see :doc:`/patterns/javascript` instead.

docs/patterns/lazyloading.rst

@@ -93,7 +93,7 @@ write this by having a function that calls into
 name and a dot, and by wrapping `view_func` in a `LazyView` as needed.  ::
 
     def url(import_name, url_rules=[], **options):
-        view = LazyView('yourapplication.' + import_name)
+        view = LazyView(f"yourapplication.{import_name}")
         for url_rule in url_rules:
             app.add_url_rule(url_rule, view_func=view, **options)
 

docs/patterns/mongoengine.rst

@@ -10,8 +10,7 @@ A running MongoDB server and `Flask-MongoEngine`_ are required. ::
     pip install flask-mongoengine
 
 .. _MongoEngine: http://mongoengine.org
-.. _Flask-MongoEngine: https://flask-mongoengine.readthedocs.io
-
+.. _Flask-MongoEngine: https://docs.mongoengine.org/projects/flask-mongoengine/en/latest/
 
 Configuration
 -------------
@@ -80,7 +79,7 @@ Queries
 Use the class ``objects`` attribute to make queries. A keyword argument
 looks for an equal value on the field. ::
 
-    bttf = Movies.objects(title="Back To The Future").get_or_404()
+    bttf = Movie.objects(title="Back To The Future").get_or_404()
 
 Query operators may be used by concatenating them with the field name
 using a double-underscore. ``objects``, and queries returned by

docs/patterns/mongokit.rst

@@ -1,7 +0,0 @@
-:orphan:
-
-MongoDB with MongoKit
-=====================
-
-MongoKit is no longer maintained. See :doc:`/patterns/mongoengine`
-instead.

docs/patterns/packages.rst

@@ -1,7 +1,5 @@
-.. _larger-applications:
-
-Larger Applications
-===================
+Large Applications as Packages
+==============================
 
 Imagine a simple flask application structure that looks like this::
 
@@ -17,7 +15,7 @@ Imagine a simple flask application structure that looks like this::
 
 While this is fine for small applications, for larger applications
 it's a good idea to use a package instead of a module.
-The :ref:`tutorial <tutorial>` is structured to use the package pattern,
+The :doc:`/tutorial/index` is structured to use the package pattern,
 see the :gh:`example code <examples/tutorial>`.
 
 Simple Packages
@@ -44,36 +42,34 @@ You should then end up with something like that::
 But how do you run your application now?  The naive ``python
 yourapplication/__init__.py`` will not work.  Let's just say that Python
 does not want modules in packages to be the startup file.  But that is not
-a big problem, just add a new file called :file:`setup.py` next to the inner
-:file:`yourapplication` folder with the following contents::
+a big problem, just add a new file called :file:`pyproject.toml` next to the inner
+:file:`yourapplication` folder with the following contents:
 
-    from setuptools import setup
+.. code-block:: toml
 
-    setup(
-        name='yourapplication',
-        packages=['yourapplication'],
-        include_package_data=True,
-        install_requires=[
-            'flask',
-        ],
-    )
+    [project]
+    name = "yourapplication"
+    dependencies = [
+        "flask",
+    ]
 
-In order to run the application you need to export an environment variable
-that tells Flask where to find the application instance::
+    [build-system]
+    requires = ["flit_core<4"]
+    build-backend = "flit_core.buildapi"
 
-    export FLASK_APP=yourapplication
+Install your application so it is importable:
 
-If you are outside of the project directory make sure to provide the exact
-path to your application directory. Similarly you can turn on the
-development features like this::
+.. code-block:: text
 
-    export FLASK_ENV=development
+    $ pip install -e .
 
-In order to install and run the application you need to issue the following
-commands::
+To use the ``flask`` command and run your application you need to set
+the ``--app`` option that tells Flask where to find the application
+instance:
 
-    pip install -e .
-    flask run
+.. code-block:: text
+
+    $ flask --app yourapplication run
 
 What did we gain from this?  Now we can restructure the application a bit
 into multiple modules.  The only thing you have to remember is the
@@ -105,7 +101,7 @@ And this is what :file:`views.py` would look like::
 You should then end up with something like that::
 
     /yourapplication
-        setup.py
+        pyproject.toml
         /yourapplication
             __init__.py
             views.py
@@ -127,12 +123,6 @@ You should then end up with something like that::
    ensuring the module is imported and we are doing that at the bottom of
    the file.
 
-   There are still some problems with that approach but if you want to use
-   decorators there is no way around that.  Check out the
-   :ref:`becomingbig` section for some inspiration how to deal with that.
-
-
-.. _working-with-modules:
 
 Working with Blueprints
 -----------------------
@@ -140,4 +130,4 @@ Working with Blueprints
 If you have larger applications it's recommended to divide them into
 smaller groups where each group is implemented with the help of a
 blueprint.  For a gentle introduction into this topic refer to the
-:ref:`blueprints` chapter of the documentation.
+:doc:`/blueprints` chapter of the documentation.

docs/patterns/requestchecksum.rst

@@ -52,4 +52,4 @@ Example usage::
         files = request.files
         # At this point the hash is fully constructed.
         checksum = hash.hexdigest()
-        return 'Hash was: %s' % checksum
+        return f"Hash was: {checksum}"

docs/patterns/singlepageapplications.rst

@@ -0,0 +1,24 @@
+Single-Page Applications
+========================
+
+Flask can be used to serve Single-Page Applications (SPA) by placing static
+files produced by your frontend framework in a subfolder inside of your
+project. You will also need to create a catch-all endpoint that routes all
+requests to your SPA.
+
+The following example demonstrates how to serve an SPA along with an API::
+
+    from flask import Flask, jsonify
+
+    app = Flask(__name__, static_folder='app', static_url_path="/app")
+
+
+    @app.route("/heartbeat")
+    def heartbeat():
+        return jsonify({"status": "healthy"})
+
+
+    @app.route('/', defaults={'path': ''})
+    @app.route('/<path:path>')
+    def catch_all(path):
+        return app.send_static_file("index.html")

docs/patterns/sqlalchemy.rst

@@ -1,12 +1,10 @@
-.. _sqlalchemy-pattern:
-
 SQLAlchemy in Flask
 ===================
 
 Many people prefer `SQLAlchemy`_ for database access.  In this case it's
 encouraged to use a package instead of a module for your flask application
-and drop the models into a separate module (:ref:`larger-applications`).
-While that is not necessary, it makes a lot of sense.
+and drop the models into a separate module (:doc:`packages`). While that
+is not necessary, it makes a lot of sense.
 
 There are four very common ways to use SQLAlchemy.  I will outline each
 of them here:
@@ -36,10 +34,9 @@ official documentation on the `declarative`_ extension.
 Here's the example :file:`database.py` module for your application::
 
     from sqlalchemy import create_engine
-    from sqlalchemy.orm import scoped_session, sessionmaker
-    from sqlalchemy.ext.declarative import declarative_base
+    from sqlalchemy.orm import scoped_session, sessionmaker, declarative_base
 
-    engine = create_engine('sqlite:////tmp/test.db', convert_unicode=True)
+    engine = create_engine('sqlite:////tmp/test.db')
     db_session = scoped_session(sessionmaker(autocommit=False,
                                              autoflush=False,
                                              bind=engine))
@@ -86,7 +83,7 @@ Here is an example model (put this into :file:`models.py`, e.g.)::
             self.email = email
 
         def __repr__(self):
-            return '<User %r>' % (self.name)
+            return f'<User {self.name!r}>'
 
 To create the database you can use the `init_db` function:
 
@@ -104,13 +101,12 @@ You can insert entries into the database like this:
 Querying is simple as well:
 
 >>> User.query.all()
-[<User u'admin'>]
+[<User 'admin'>]
 >>> User.query.filter(User.name == 'admin').first()
-<User u'admin'>
+<User 'admin'>
 
 .. _SQLAlchemy: https://www.sqlalchemy.org/
-.. _declarative:
-   https://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/
+.. _declarative: https://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/
 
 Manual Object Relational Mapping
 --------------------------------
@@ -127,7 +123,7 @@ Here is an example :file:`database.py` module for your application::
     from sqlalchemy import create_engine, MetaData
     from sqlalchemy.orm import scoped_session, sessionmaker
 
-    engine = create_engine('sqlite:////tmp/test.db', convert_unicode=True)
+    engine = create_engine('sqlite:////tmp/test.db')
     metadata = MetaData()
     db_session = scoped_session(sessionmaker(autocommit=False,
                                              autoflush=False,
@@ -135,9 +131,8 @@ Here is an example :file:`database.py` module for your application::
     def init_db():
         metadata.create_all(bind=engine)
 
-As in the declarative approach, you need to close the session after
-each request or application context shutdown.  Put this into your
-application module::
+As in the declarative approach, you need to close the session after each app
+context. Put this into your application module::
 
     from yourapplication.database import db_session
 
@@ -159,7 +154,7 @@ Here is an example table and model (put this into :file:`models.py`)::
             self.email = email
 
         def __repr__(self):
-            return '<User %r>' % (self.name)
+            return f'<User {self.name!r}>'
 
     users = Table('users', metadata,
         Column('id', Integer, primary_key=True),
@@ -179,7 +174,7 @@ you basically only need the engine::
 
     from sqlalchemy import create_engine, MetaData, Table
 
-    engine = create_engine('sqlite:////tmp/test.db', convert_unicode=True)
+    engine = create_engine('sqlite:////tmp/test.db')
     metadata = MetaData(bind=engine)
 
 Then you can either declare the tables in your code like in the examples
@@ -200,19 +195,19 @@ SQLAlchemy will automatically commit for us.
 To query your database, you use the engine directly or use a connection:
 
 >>> users.select(users.c.id == 1).execute().first()
-(1, u'admin', u'admin@localhost')
+(1, 'admin', 'admin@localhost')
 
 These results are also dict-like tuples:
 
 >>> r = users.select(users.c.id == 1).execute().first()
 >>> r['name']
-u'admin'
+'admin'
 
 You can also pass strings of SQL statements to the
 :meth:`~sqlalchemy.engine.base.Connection.execute` method:
 
 >>> engine.execute('select * from users where id = :1', [1]).first()
-(1, u'admin', u'admin@localhost')
+(1, 'admin', 'admin@localhost')
 
 For more information about SQLAlchemy, head over to the
 `website <https://www.sqlalchemy.org/>`_.

docs/patterns/sqlite3.rst

@@ -1,11 +1,9 @@
-.. _sqlite3:
-
 Using SQLite 3 with Flask
 =========================
 
-In Flask you can easily implement the opening of database connections on
-demand and closing them when the context dies (usually at the end of the
-request).
+You can implement a few functions to work with a SQLite connection during a
+request context. The connection is created the first time it's accessed,
+reused on subsequent access, until it is closed when the request context ends.
 
 Here is a simple example of how you can use SQLite 3 with Flask::
 
@@ -32,10 +30,6 @@ or create an application context itself.  At that point the ``get_db``
 function can be used to get the current database connection.  Whenever the
 context is destroyed the database connection will be terminated.
 
-Note: if you use Flask 0.9 or older you need to use
-``flask._app_ctx_stack.top`` instead of ``g`` as the :data:`flask.g`
-object was bound to the request and not application context.
-
 Example::
 
     @app.route('/')
@@ -62,7 +56,6 @@ the application context by hand::
     with app.app_context():
         # now you can use get_db()
 
-.. _easy-querying:
 
 Easy Querying
 -------------
@@ -116,16 +109,16 @@ raw cursor and connection objects.
 Here is how you can use it::
 
     for user in query_db('select * from users'):
-        print user['username'], 'has the id', user['user_id']
+        print(user['username'], 'has the id', user['user_id'])
 
 Or if you just want a single result::
 
     user = query_db('select * from users where username = ?',
                     [the_username], one=True)
     if user is None:
-        print 'No such user'
+        print('No such user')
     else:
-        print the_username, 'has the id', user['user_id']
+        print(the_username, 'has the id', user['user_id'])
 
 To pass variable parts to the SQL statement, use a question mark in the
 statement and pass in the arguments as a list.  Never directly add them to

docs/patterns/streaming.rst

@@ -8,6 +8,21 @@ roundtrip to the filesystem?
 
 The answer is by using generators and direct responses.
 
+HTTP Response Behavior
+----------------------
+
+**Headers cannot be changed after the streaming response starts.**
+
+When using streaming, it's important to be aware of the order than an HTTP
+response is sent. All headers must be sent first, then the body. More headers
+cannot be sent after the body has begun. Therefore, you must make sure all
+headers are set before starting the response, outside the generator.
+
+In particular, if the generator will access ``session``, be sure to do so in the
+view as well so that the ``Vary: cookie`` header will be set. Do not modify the
+session in the generator, as the ``Set-Cookie`` header will already be sent.
+
+
 Basic Usage
 -----------
 
@@ -15,14 +30,12 @@ This is a basic view function that generates a lot of CSV data on the fly.
 The trick is to have an inner function that uses a generator to generate
 data and to then invoke that function and pass it to a response object::
 
-    from flask import Response
-
     @app.route('/large.csv')
     def generate_large_csv():
         def generate():
             for row in iter_all_rows():
-                yield ','.join(row) + '\n'
-        return Response(generate(), mimetype='text/csv')
+                yield f"{','.join(row)}\n"
+        return generate(), {"Content-Type": "text/csv"}
 
 Each ``yield`` expression is directly sent to the browser.  Note though
 that some WSGI middlewares might break streaming, so be careful there in
@@ -31,54 +44,57 @@ debug environments with profilers and other things you might have enabled.
 Streaming from Templates
 ------------------------
 
-The Jinja2 template engine also supports rendering templates piece by
-piece.  This functionality is not directly exposed by Flask because it is
-quite uncommon, but you can easily do it yourself::
+The Jinja template engine supports rendering a template piece by
+piece, returning an iterator of strings. Flask provides the
+:func:`~flask.stream_template` and :func:`~flask.stream_template_string`
+functions to make this easier to use.
 
-    from flask import Response
+.. code-block:: python
 
-    def stream_template(template_name, **context):
-        app.update_template_context(context)
-        t = app.jinja_env.get_template(template_name)
-        rv = t.stream(context)
-        rv.enable_buffering(5)
-        return rv
+    from flask import stream_template
 
-    @app.route('/my-large-page.html')
-    def render_large_template():
-        rows = iter_all_rows()
-        return Response(stream_template('the_template.html', rows=rows))
+    @app.get("/timeline")
+    def timeline():
+        return stream_template("timeline.html")
+
+The parts yielded by the render stream tend to match statement blocks in
+the template.
 
-The trick here is to get the template object from the Jinja2 environment
-on the application and to call :meth:`~jinja2.Template.stream` instead of
-:meth:`~jinja2.Template.render` which returns a stream object instead of a
-string.  Since we're bypassing the Flask template render functions and
-using the template object itself we have to make sure to update the render
-context ourselves by calling :meth:`~flask.Flask.update_template_context`.
-The template is then evaluated as the stream is iterated over.  Since each
-time you do a yield the server will flush the content to the client you
-might want to buffer up a few items in the template which you can do with
-``rv.enable_buffering(size)``.  ``5`` is a sane default.
 
 Streaming with Context
 ----------------------
 
-.. versionadded:: 0.9
+The :data:`.request` proxy will not be active while the generator is
+running, because the app has already returned control to the WSGI server at that
+point. If you try to access ``request``, you'll get a ``RuntimeError``.
 
-Note that when you stream data, the request context is already gone the
-moment the function executes.  Flask 0.9 provides you with a helper that
-can keep the request context around during the execution of the
-generator::
+If your generator function relies on data in ``request``, use the
+:func:`.stream_with_context` wrapper. This will keep the request context active
+during the generator.
 
-    from flask import stream_with_context, request, Response
+.. code-block:: python
+
+    from flask import stream_with_context, request
+    from markupsafe import escape
 
     @app.route('/stream')
     def streamed_response():
         def generate():
-            yield 'Hello '
-            yield request.args['name']
-            yield '!'
-        return Response(stream_with_context(generate()))
+            yield '<p>Hello '
+            yield escape(request.args['name'])
+            yield '!</p>'
+        return stream_with_context(generate())
 
-Without the :func:`~flask.stream_with_context` function you would get a
-:class:`RuntimeError` at that point.
+It can also be used as a decorator.
+
+.. code-block:: python
+
+    @stream_with_context
+    def generate():
+        ...
+
+    return generate()
+
+The :func:`~flask.stream_template` and
+:func:`~flask.stream_template_string` functions automatically
+use :func:`~flask.stream_with_context` if a request is active.

docs/patterns/templateinheritance.rst

@@ -1,5 +1,3 @@
-.. _template-inheritance:
-
 Template Inheritance
 ====================