From 062e644aae4299a320aeac59085df4c020ba6c81 Mon Sep 17 00:00:00 2001
From: Richard Si <63936253+ichard26@users.noreply.github.com>
Date: Mon, 5 Sep 2022 16:27:05 -0400
Subject: [PATCH] Mitigate deprecation of aiohttp's `@middleware` decorator
 (#3259)

This is deprecated since aiohttp 4.0. If it doesn't exist just define a
no-op decorator that does nothing (after the other aiohttp imports
though!). By doing this, it's safe to ignore the DeprecationWarning
without needing to require the latest aiohttp once they remove
`@middleware`.
---
 pyproject.toml            |  3 +++
 src/blackd/middlewares.py | 18 ++++++++++++++----
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index 813e86b..849891f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -105,6 +105,9 @@ filterwarnings = [
     # this is mitigated by a try/catch in https://github.com/psf/black/pull/2974/
     # this ignore can be removed when support for aiohttp 3.7 is dropped.
     '''ignore:Decorator `@unittest_run_loop` is no longer needed in aiohttp 3\.8\+:DeprecationWarning''',
+    # this is mitigated by a try/catch in https://github.com/psf/black/pull/3198/
+    # this ignore can be removed when support for aiohttp 3.x is dropped.
+    '''ignore:Middleware decorator is deprecated since 4\.0 and its behaviour is default, you can simply remove this decorator:DeprecationWarning''',
     # this is mitigated by https://github.com/python/cpython/issues/79071 in python 3.8+
     # this ignore can be removed when support for 3.7 is dropped.
     '''ignore:Bare functions are deprecated, use async ones:DeprecationWarning''',
diff --git a/src/blackd/middlewares.py b/src/blackd/middlewares.py
index e71f508..370e0ae 100644
--- a/src/blackd/middlewares.py
+++ b/src/blackd/middlewares.py
@@ -1,15 +1,25 @@
-from typing import Awaitable, Callable, Iterable
+from typing import TYPE_CHECKING, Any, Awaitable, Callable, Iterable, TypeVar
 
-from aiohttp.web_middlewares import middleware
 from aiohttp.web_request import Request
 from aiohttp.web_response import StreamResponse
 
+if TYPE_CHECKING:
+    F = TypeVar("F", bound=Callable[..., Any])
+    middleware: Callable[[F], F]
+else:
+    try:
+        from aiohttp.web_middlewares import middleware
+    except ImportError:
+        # @middleware is deprecated and its behaviour is the default since aiohttp 4.0
+        # so if it doesn't exist anymore, define a no-op for forward compatibility.
+        middleware = lambda x: x  # noqa: E731
+
 Handler = Callable[[Request], Awaitable[StreamResponse]]
 Middleware = Callable[[Request, Handler], Awaitable[StreamResponse]]
 
 
 def cors(allow_headers: Iterable[str]) -> Middleware:
-    @middleware  # type: ignore[misc]
+    @middleware
     async def impl(request: Request, handler: Handler) -> StreamResponse:
         is_options = request.method == "OPTIONS"
         is_preflight = is_options and "Access-Control-Request-Method" in request.headers
@@ -32,4 +42,4 @@ def cors(allow_headers: Iterable[str]) -> Middleware:
 
         return resp
 
-    return impl  # type: ignore[no-any-return]
+    return impl
-- 
2.39.5