Fix routing type-check failures in pre-commit.

Normalize request handler typing in routing utils and explicitly type APIRoute.response_field to satisfy mypy and ty hooks.

Made-with: Cursor

fastapi/routing_routes.py

@@ -163,6 +163,7 @@ class APIRoute(routing.Route):
         if isinstance(status_code, IntEnum):
             status_code = int(status_code)
         self.status_code = status_code
+        self.response_field: ModelField | None
         if self.response_model:
             assert is_body_allowed_for_status_code(status_code), (
                 f"Status code {status_code} must not have a response body"
@@ -174,7 +175,7 @@ class APIRoute(routing.Route):
                 mode="serialization",
             )
         else:
-            self.response_field = None  # type: ignore
+            self.response_field = None
         if self.stream_item_type:
             stream_item_name = "StreamItem_" + self.unique_id
             self.stream_item_field: ModelField | None = create_model_field(

fastapi/routing_utils.py

@@ -15,7 +15,7 @@ from contextlib import (
     AsyncExitStack,
     asynccontextmanager,
 )
-from typing import Any, TypeVar
+from typing import Any, TypeVar, cast
 
 from fastapi._compat import ModelField
 from fastapi.dependencies.models import Dependant
@@ -40,9 +40,15 @@ _T = TypeVar("_T")
 def request_response(
     func: Callable[[Request], Awaitable[Response] | Response],
 ) -> ASGIApp:
-    f: Callable[[Request], Awaitable[Response]] = (
+    if is_async_callable(func):
-        func if is_async_callable(func) else functools.partial(run_in_threadpool, func)  # type: ignore[call-arg]
+        f: Callable[[Request], Awaitable[Response]] = cast(
+            Callable[[Request], Awaitable[Response]], func
         )
+    else:
+        sync_func = cast(Callable[[Request], Response], func)
+
+        async def f(request: Request) -> Response:
+            return await run_in_threadpool(sync_func, request)
 
     async def app(scope: Scope, receive: Receive, send: Send) -> None:
         request = Request(scope, receive, send)