Improve middleware performance

CHANGES/9200.breaking.rst

@@ -0,0 +1,3 @@
+Improved middleware performance -- by :user:`bdraco`.
+
+The ``set_current_app`` method was removed from ``UrlMappingMatchInfo`` because it is no longer used, and it was unlikely external caller would ever use it.

aiohttp/web_middlewares.py

@@ -115,7 +115,12 @@ async def impl(request: Request, handler: Handler) -> StreamResponse:
 
 def _fix_request_current_app(app: "Application") -> Middleware:
     async def impl(request: Request, handler: Handler) -> StreamResponse:
-        with request.match_info.set_current_app(app):
+        match_info = request.match_info
+        prev = match_info.current_app
+        match_info.current_app = app
+        try:
             return await handler(request)
+        finally:
+            match_info.current_app = prev
 
     return impl

aiohttp/web_urldispatcher.py

@@ -8,7 +8,6 @@
 import os
 import re
 import sys
-from contextlib import contextmanager
 from pathlib import Path
 from types import MappingProxyType
 from typing import (
@@ -271,21 +270,16 @@ def current_app(self) -> "Application":
         assert app is not None
         return app
 
-    @contextmanager
-    def set_current_app(self, app: "Application") -> Generator[None, None, None]:
+    @current_app.setter
+    def current_app(self, app: "Application") -> None:
         if DEBUG:  # pragma: no cover
             if app not in self._apps:
                 raise RuntimeError(
                     "Expected one of the following apps {!r}, got {!r}".format(
                         self._apps, app
                     )
                 )
-        prev = self._current_app
         self._current_app = app
-        try:
-            yield
-        finally:
-            self._current_app = prev
 
     def freeze(self) -> None:
         self._frozen = True