Add type hints to tutorial and Javascript examples

- Add return type annotations and parameter
  types
 - Import necessary typing modules (Optional,
 Union, Flask, Response)
 - Improve code readability and IDE support for
   examples
 - All existing tests continue to pass

examples/javascript/js_example/views.py

@@ -1,18 +1,19 @@
 from flask import jsonify
 from flask import render_template
 from flask import request
+from flask import Response
 
 from . import app
 
 
 @app.route("/", defaults={"js": "fetch"})
 @app.route("/<any(xhr, jquery, fetch):js>")
-def index(js):
+def index(js: str) -> str:
     return render_template(f"{js}.html", js=js)
 
 
 @app.route("/add", methods=["POST"])
-def add():
+def add() -> Response:
     a = request.form.get("a", 0, type=float)
     b = request.form.get("b", 0, type=float)
     return jsonify(result=a + b)

examples/tutorial/flaskr/auth.py

@@ -1,4 +1,6 @@
 import functools
+from typing import Callable, Union
+from werkzeug.wrappers import Response
 
 from flask import Blueprint
 from flask import flash
@@ -16,7 +18,7 @@ from .db import get_db
 bp = Blueprint("auth", __name__, url_prefix="/auth")
 
 
-def login_required(view):
+def login_required(view: Callable) -> Callable:
     """View decorator that redirects anonymous users to the login page."""
 
     @functools.wraps(view)
@@ -30,7 +32,7 @@ def login_required(view):
 
 
 @bp.before_app_request
-def load_logged_in_user():
+def load_logged_in_user() -> None:
     """If a user id is stored in the session, load the user object from
     the database into ``g.user``."""
     user_id = session.get("user_id")
@@ -44,7 +46,7 @@ def load_logged_in_user():
 
 
 @bp.route("/register", methods=("GET", "POST"))
-def register():
+def register() -> Union[str, Response]:
     """Register a new user.
 
     Validates that the username is not already taken. Hashes the
@@ -82,7 +84,7 @@ def register():
 
 
 @bp.route("/login", methods=("GET", "POST"))
-def login():
+def login() -> Union[str, Response]:
     """Log in a registered user by adding the user id to the session."""
     if request.method == "POST":
         username = request.form["username"]
@@ -110,7 +112,7 @@ def login():
 
 
 @bp.route("/logout")
-def logout():
+def logout() -> Union[str, Response]:
     """Clear the current session, including the stored user id."""
     session.clear()
     return redirect(url_for("index"))

examples/tutorial/flaskr/blog.py

@@ -1,3 +1,7 @@
+import sqlite3
+from typing import Optional, Union
+
+from werkzeug.wrappers import Response
 from flask import Blueprint
 from flask import flash
 from flask import g
@@ -14,7 +18,7 @@ bp = Blueprint("blog", __name__)
 
 
 @bp.route("/")
-def index():
+def index() -> str:
     """Show all the posts, most recent first."""
     db = get_db()
     posts = db.execute(
@@ -25,7 +29,7 @@ def index():
     return render_template("blog/index.html", posts=posts)
 
 
-def get_post(id, check_author=True):
+def get_post(id: int, check_author: bool = True) -> Optional[sqlite3.Row]:
     """Get a post and its author by id.
 
     Checks that the id exists and optionally that the current user is
@@ -59,7 +63,7 @@ def get_post(id, check_author=True):
 
 @bp.route("/create", methods=("GET", "POST"))
 @login_required
-def create():
+def create() -> Union[str, Response]:
     """Create a new post for the current user."""
     if request.method == "POST":
         title = request.form["title"]
@@ -85,7 +89,7 @@ def create():
 
 @bp.route("/<int:id>/update", methods=("GET", "POST"))
 @login_required
-def update(id):
+def update(id: int) -> Union[str, Response]:
     """Update a post if the current user is the author."""
     post = get_post(id)
 
@@ -112,7 +116,7 @@ def update(id):
 
 @bp.route("/<int:id>/delete", methods=("POST",))
 @login_required
-def delete(id):
+def delete(id: int) -> Union[str, Response]:
     """Delete a post.
 
     Ensures that the post exists and that the logged in user is the

examples/tutorial/flaskr/db.py

@@ -5,8 +5,10 @@ import click
 from flask import current_app
 from flask import g
 
+from flask import Flask
 
-def get_db():
+
+def get_db() -> sqlite3.Connection:
     """Connect to the application's configured database. The connection
     is unique for each request and will be reused if this is called
     again.
@@ -20,7 +22,7 @@ def get_db():
     return g.db
 
 
-def close_db(e=None):
+def close_db(e=None) -> None:
     """If this request connected to the database, close the
     connection.
     """
@@ -30,7 +32,7 @@ def close_db(e=None):
         db.close()
 
 
-def init_db():
+def init_db() -> None:
     """Clear existing data and create new tables."""
     db = get_db()
 
@@ -39,7 +41,7 @@ def init_db():
 
 
 @click.command("init-db")
-def init_db_command():
+def init_db_command() -> None:
     """Clear existing data and create new tables."""
     init_db()
     click.echo("Initialized the database.")
@@ -48,7 +50,7 @@ def init_db_command():
 sqlite3.register_converter("timestamp", lambda v: datetime.fromisoformat(v.decode()))
 
 
-def init_app(app):
+def init_app(app: Flask) -> None:
     """Register database functions with the Flask app. This is called by
     the application factory.
     """