[PR #9976/2b40f6b7 backport][3.11] Restore only construct the allowed_methods set once for a StaticResource (#9979)

Co-authored-by: J. Nick Koston <[email protected]>

Author: patchback[bot]

CHANGES/9972.bugfix.rst

@@ -1,3 +1 @@
-Reverted an optimization to avoid rebuilding the allowed methods for ``StaticResource`` on every request -- by :user:`bdraco`.
-
-``aiohttp-cors`` needs to be able to modify the allowed methods at run time via this internal.
+Fixed ``StaticResource`` not allowing the ``OPTIONS`` method after calling ``set_options_route`` -- by :user:`bdraco`.

CHANGES/9976.bugfix.rst

@@ -0,0 +1 @@
+9972.bugfix.rst

aiohttp/web_urldispatcher.py

@@ -580,6 +580,7 @@ def __init__(
                 "HEAD", self._handle, self, expect_handler=expect_handler
             ),
         }
+        self._allowed_methods = set(self._routes)
 
     def url_for(  # type: ignore[override]
         self,
@@ -642,14 +643,15 @@ def set_options_route(self, handler: Handler) -> None:
         self._routes["OPTIONS"] = ResourceRoute(
             "OPTIONS", handler, self, expect_handler=self._expect_handler
         )
+        self._allowed_methods.add("OPTIONS")
 
     async def resolve(self, request: Request) -> _Resolve:
         path = request.rel_url.path_safe
         method = request.method
         if not path.startswith(self._prefix2) and path != self._prefix:
             return None, set()
 
-        allowed_methods = set(self._routes)
+        allowed_methods = self._allowed_methods
         if method not in allowed_methods:
             return None, allowed_methods
 

tests/test_urldispatch.py

@@ -498,6 +498,7 @@ async def test_add_static_access_resources(router: web.UrlDispatcher) -> None:
         "/st", pathlib.Path(aiohttp.__file__).parent, name="static"
     )
     resource._routes[hdrs.METH_OPTIONS] = resource._routes[hdrs.METH_GET]
+    resource._allowed_methods.add(hdrs.METH_OPTIONS)
     mapping, allowed_methods = await resource.resolve(
         make_mocked_request("OPTIONS", "/st/path")
     )