From 7f87f3dd93baf45d5f69f02a2dcf4493dfc4a1be Mon Sep 17 00:00:00 2001 From: pgjones Date: Sun, 2 May 2021 20:49:46 +0100 Subject: [PATCH] Simplify the async handling code Firstly `run_sync` was a misleading name as it didn't run anything, instead I think `async_to_sync` is much clearer as it converts a coroutine function to a function. (Name stolen from asgiref). Secondly trying to run the ensure_sync during registration made the code more complex and brittle, e.g. the _flask_async_wrapper usage. This was done to pay any setup costs during registration rather than runtime, however this only saved a iscoroutne check. It allows the weirdness of the Blueprint and Scaffold ensure_sync methods to be removed. Switching to runtime ensure_sync usage provides a method for extensions to also support async, as now documented. --- docs/async-await.rst | 15 +++++++++++++++ src/flask/app.py | 30 ++++++++++++++---------------- src/flask/blueprints.py | 40 ++++++++-------------------------------- src/flask/helpers.py | 19 +++++++++---------- src/flask/scaffold.py | 13 +++++-------- tests/test_async.py | 4 ++-- 6 files changed, 53 insertions(+), 68 deletions(-) diff --git a/docs/async-await.rst b/docs/async-await.rst index 23b418de..34751d47 100644 --- a/docs/async-await.rst +++ b/docs/async-await.rst @@ -92,6 +92,21 @@ 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. diff --git a/src/flask/app.py b/src/flask/app.py index 7afb0a1e..7bc952b1 100644 --- a/src/flask/app.py +++ b/src/flask/app.py @@ -35,12 +35,12 @@ from .globals import _request_ctx_stack from .globals import g from .globals import request from .globals import session +from .helpers import async_to_sync from .helpers import get_debug_flag from .helpers import get_env from .helpers import get_flashed_messages from .helpers import get_load_dotenv from .helpers import locked_cached_property -from .helpers import run_async from .helpers import url_for from .json import jsonify from .logging import create_logger @@ -1080,14 +1080,12 @@ class Flask(Scaffold): self.url_map.add(rule) if view_func is not None: old_func = self.view_functions.get(endpoint) - if getattr(old_func, "_flask_sync_wrapper", False): - old_func = old_func.__wrapped__ # type: ignore if old_func is not None and old_func != view_func: raise AssertionError( "View function mapping is overwriting an existing" f" endpoint function: {endpoint}" ) - self.view_functions[endpoint] = self.ensure_sync(view_func) + self.view_functions[endpoint] = view_func @setupmethod def template_filter(self, name: t.Optional[str] = None) -> t.Callable: @@ -1208,7 +1206,7 @@ class Flask(Scaffold): .. versionadded:: 0.8 """ - self.before_first_request_funcs.append(self.ensure_sync(f)) + self.before_first_request_funcs.append(f) return f @setupmethod @@ -1241,7 +1239,7 @@ class Flask(Scaffold): .. versionadded:: 0.9 """ - self.teardown_appcontext_funcs.append(self.ensure_sync(f)) + self.teardown_appcontext_funcs.append(f) return f @setupmethod @@ -1308,7 +1306,7 @@ class Flask(Scaffold): handler = self._find_error_handler(e) if handler is None: return e - return handler(e) + return self.ensure_sync(handler)(e) def trap_http_exception(self, e: Exception) -> bool: """Checks if an HTTP exception should be trapped or not. By default @@ -1375,7 +1373,7 @@ class Flask(Scaffold): if handler is None: raise - return handler(e) + return self.ensure_sync(handler)(e) def handle_exception(self, e: Exception) -> Response: """Handle an exception that did not have an error handler @@ -1422,7 +1420,7 @@ class Flask(Scaffold): handler = self._find_error_handler(server_error) if handler is not None: - server_error = handler(server_error) + server_error = self.ensure_sync(handler)(server_error) return self.finalize_request(server_error, from_error_handler=True) @@ -1484,7 +1482,7 @@ class Flask(Scaffold): ): return self.make_default_options_response() # otherwise dispatch to the handler for that endpoint - return self.view_functions[rule.endpoint](**req.view_args) + return self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args) def full_dispatch_request(self) -> Response: """Dispatches the request and on top of that performs request @@ -1545,7 +1543,7 @@ class Flask(Scaffold): if self._got_first_request: return for func in self.before_first_request_funcs: - func() + self.ensure_sync(func)() self._got_first_request = True def make_default_options_response(self) -> Response: @@ -1581,7 +1579,7 @@ class Flask(Scaffold): .. versionadded:: 2.0 """ if iscoroutinefunction(func): - return run_async(func) + return async_to_sync(func) return func @@ -1807,7 +1805,7 @@ class Flask(Scaffold): if bp in self.before_request_funcs: funcs = chain(funcs, self.before_request_funcs[bp]) for func in funcs: - rv = func() + rv = self.ensure_sync(func)() if rv is not None: return rv @@ -1834,7 +1832,7 @@ class Flask(Scaffold): if None in self.after_request_funcs: funcs = chain(funcs, reversed(self.after_request_funcs[None])) for handler in funcs: - response = handler(response) + response = self.ensure_sync(handler)(response) if not self.session_interface.is_null_session(ctx.session): self.session_interface.save_session(self, ctx.session, response) return response @@ -1871,7 +1869,7 @@ class Flask(Scaffold): if bp in self.teardown_request_funcs: funcs = chain(funcs, reversed(self.teardown_request_funcs[bp])) for func in funcs: - func(exc) + self.ensure_sync(func)(exc) request_tearing_down.send(self, exc=exc) def do_teardown_appcontext( @@ -1894,7 +1892,7 @@ class Flask(Scaffold): if exc is _sentinel: exc = sys.exc_info()[1] for func in reversed(self.teardown_appcontext_funcs): - func(exc) + self.ensure_sync(func)(exc) appcontext_tearing_down.send(self, exc=exc) def app_context(self) -> AppContext: diff --git a/src/flask/blueprints.py b/src/flask/blueprints.py index a2b6c0f5..5fb84d86 100644 --- a/src/flask/blueprints.py +++ b/src/flask/blueprints.py @@ -292,13 +292,10 @@ class Blueprint(Scaffold): # Merge blueprint data into parent. if first_registration: - def extend(bp_dict, parent_dict, ensure_sync=False): + def extend(bp_dict, parent_dict): for key, values in bp_dict.items(): key = self.name if key is None else f"{self.name}.{key}" - if ensure_sync: - values = [app.ensure_sync(func) for func in values] - parent_dict[key].extend(values) for key, value in self.error_handler_spec.items(): @@ -307,8 +304,7 @@ class Blueprint(Scaffold): dict, { code: { - exc_class: app.ensure_sync(func) - for exc_class, func in code_values.items() + exc_class: func for exc_class, func in code_values.items() } for code, code_values in value.items() }, @@ -316,16 +312,13 @@ class Blueprint(Scaffold): app.error_handler_spec[key] = value for endpoint, func in self.view_functions.items(): - app.view_functions[endpoint] = app.ensure_sync(func) + app.view_functions[endpoint] = func - extend( - self.before_request_funcs, app.before_request_funcs, ensure_sync=True - ) - extend(self.after_request_funcs, app.after_request_funcs, ensure_sync=True) + extend(self.before_request_funcs, app.before_request_funcs) + extend(self.after_request_funcs, app.after_request_funcs) extend( self.teardown_request_funcs, app.teardown_request_funcs, - ensure_sync=True, ) extend(self.url_default_functions, app.url_default_functions) extend(self.url_value_preprocessors, app.url_value_preprocessors) @@ -478,9 +471,7 @@ class Blueprint(Scaffold): before each request, even if outside of a blueprint. """ self.record_once( - lambda s: s.app.before_request_funcs.setdefault(None, []).append( - s.app.ensure_sync(f) - ) + lambda s: s.app.before_request_funcs.setdefault(None, []).append(f) ) return f @@ -490,9 +481,7 @@ class Blueprint(Scaffold): """Like :meth:`Flask.before_first_request`. Such a function is executed before the first request to the application. """ - self.record_once( - lambda s: s.app.before_first_request_funcs.append(s.app.ensure_sync(f)) - ) + self.record_once(lambda s: s.app.before_first_request_funcs.append(f)) return f def after_app_request(self, f: AfterRequestCallable) -> AfterRequestCallable: @@ -500,9 +489,7 @@ class Blueprint(Scaffold): is executed after each request, even if outside of the blueprint. """ self.record_once( - lambda s: s.app.after_request_funcs.setdefault(None, []).append( - s.app.ensure_sync(f) - ) + lambda s: s.app.after_request_funcs.setdefault(None, []).append(f) ) return f @@ -553,14 +540,3 @@ class Blueprint(Scaffold): lambda s: s.app.url_default_functions.setdefault(None, []).append(f) ) return f - - def ensure_sync(self, f: t.Callable) -> t.Callable: - """Ensure the function is synchronous. - - Override if you would like custom async to sync behaviour in - this blueprint. Otherwise the app's - :meth:`~flask.Flask.ensure_sync` is used. - - .. versionadded:: 2.0 - """ - return f diff --git a/src/flask/helpers.py b/src/flask/helpers.py index 9e84960e..621d51e6 100644 --- a/src/flask/helpers.py +++ b/src/flask/helpers.py @@ -6,7 +6,6 @@ import typing as t import warnings from datetime import timedelta from functools import update_wrapper -from functools import wraps from threading import RLock import werkzeug.utils @@ -803,10 +802,15 @@ def is_ip(value: str) -> bool: return False -def run_async(func: t.Callable[..., t.Coroutine]) -> t.Callable[..., t.Any]: - """Return a sync function that will run the coroutine function *func*.""" +def async_to_sync(func: t.Callable[..., t.Coroutine]) -> t.Callable[..., t.Any]: + """Return a sync function that will run the coroutine function *func*. + + This can be used as so + + result = async_to_async(func)(*args, **kwargs) + """ try: - from asgiref.sync import async_to_sync + from asgiref.sync import async_to_sync as asgiref_async_to_sync except ImportError: raise RuntimeError( "Install Flask with the 'async' extra in order to use async views." @@ -818,9 +822,4 @@ def run_async(func: t.Callable[..., t.Coroutine]) -> t.Callable[..., t.Any]: "Async cannot be used with this combination of Python & Greenlet versions." ) - @wraps(func) - def wrapper(*args: t.Any, **kwargs: t.Any) -> t.Any: - return async_to_sync(func)(*args, **kwargs) - - wrapper._flask_sync_wrapper = True # type: ignore - return wrapper + return asgiref_async_to_sync(func) diff --git a/src/flask/scaffold.py b/src/flask/scaffold.py index d40dfdd8..56d37ddd 100644 --- a/src/flask/scaffold.py +++ b/src/flask/scaffold.py @@ -521,7 +521,7 @@ class Scaffold: """ def decorator(f): - self.view_functions[endpoint] = self.ensure_sync(f) + self.view_functions[endpoint] = f return f return decorator @@ -545,7 +545,7 @@ class Scaffold: return value from the view, and further request handling is stopped. """ - self.before_request_funcs.setdefault(None, []).append(self.ensure_sync(f)) + self.before_request_funcs.setdefault(None, []).append(f) return f @setupmethod @@ -561,7 +561,7 @@ class Scaffold: should not be used for actions that must execute, such as to close resources. Use :meth:`teardown_request` for that. """ - self.after_request_funcs.setdefault(None, []).append(self.ensure_sync(f)) + self.after_request_funcs.setdefault(None, []).append(f) return f @setupmethod @@ -600,7 +600,7 @@ class Scaffold: debugger can still access it. This behavior can be controlled by the ``PRESERVE_CONTEXT_ON_EXCEPTION`` configuration variable. """ - self.teardown_request_funcs.setdefault(None, []).append(self.ensure_sync(f)) + self.teardown_request_funcs.setdefault(None, []).append(f) return f @setupmethod @@ -706,7 +706,7 @@ class Scaffold: " instead." ) - self.error_handler_spec[None][code][exc_class] = self.ensure_sync(f) + self.error_handler_spec[None][code][exc_class] = f @staticmethod def _get_exc_class_and_code( @@ -734,9 +734,6 @@ class Scaffold: else: return exc_class, None - def ensure_sync(self, func: t.Callable) -> t.Callable: - raise NotImplementedError() - def _endpoint_from_view_func(view_func: t.Callable) -> str: """Internal helper that returns the default endpoint for a given diff --git a/tests/test_async.py b/tests/test_async.py index 8c096f69..798eed85 100644 --- a/tests/test_async.py +++ b/tests/test_async.py @@ -6,7 +6,7 @@ import pytest from flask import Blueprint from flask import Flask from flask import request -from flask.helpers import run_async +from flask.helpers import async_to_sync pytest.importorskip("asgiref") @@ -137,4 +137,4 @@ def test_async_before_after_request(): @pytest.mark.skipif(sys.version_info >= (3, 7), reason="should only raise Python < 3.7") def test_async_runtime_error(): with pytest.raises(RuntimeError): - run_async(None) + async_to_sync(None)