Apply suggestion from @Kludex

On Python 3.11+, `loop.create_task` accepts a `context` kwarg
directly, avoiding the `Context().run()` indirection. This was
already noted as a TODO in the codebase.

Ref: https://github.com/encode/uvicorn/discussions/2794

uvicorn/protocols/http/h11_impl.py

@@ -4,6 +4,7 @@ import asyncio
 import contextvars
 import http
 import logging
+import sys
 from collections.abc import Callable
 from typing import Any, Literal, cast
 from urllib.parse import unquote
@@ -249,12 +250,12 @@ class H11Protocol(asyncio.Protocol):
                     message_event=asyncio.Event(),
                     on_response=self.on_response_complete,
                 )
-                # For the asyncio loop, we need to explicitly start with an empty context
-                # as it can be polluted from previous ASGI runs.
-                # See https://github.com/python/cpython/issues/140947 for details.
-                task = contextvars.Context().run(self.loop.create_task, self.cycle.run_asgi(app))
-                # TODO: Replace the line above with the line below for Python >= 3.11
-                # task = self.loop.create_task(self.cycle.run_asgi(app), context=contextvars.Context())
+                # Start with an empty context to prevent context variable pollution
+                # between ASGI runs. See https://github.com/python/cpython/issues/140947
+                if sys.version_info >= (3, 11):  # pragma: no cover
+                    task = self.loop.create_task(self.cycle.run_asgi(app), context=contextvars.Context())
+                else:  # pragma: no cover
+                    task = contextvars.Context().run(self.loop.create_task, self.cycle.run_asgi(app))
                 task.add_done_callback(self.tasks.discard)
                 self.tasks.add(task)
 

uvicorn/protocols/http/httptools_impl.py

@@ -5,6 +5,7 @@ import contextvars
 import http
 import logging
 import re
+import sys
 import urllib
 from asyncio.events import TimerHandle
 from collections import deque
@@ -289,12 +290,12 @@ class HttpToolsProtocol(asyncio.Protocol):
         )
         if existing_cycle is None or existing_cycle.response_complete:
             # Standard case - start processing the request.
-            # For the asyncio loop, we need to explicitly start with an empty context
-            # as it can be polluted from previous ASGI runs.
-            # See https://github.com/python/cpython/issues/140947 for details.
-            task = contextvars.Context().run(self.loop.create_task, self.cycle.run_asgi(app))
-            # TODO: Replace the line above with the line below for Python >= 3.11
-            # task = self.loop.create_task(self.cycle.run_asgi(app), context=contextvars.Context())
+            # Start with an empty context to prevent context variable pollution
+            # between ASGI runs. See https://github.com/python/cpython/issues/140947
+            if sys.version_info >= (3, 11):  # pragma: no cover
+                task = self.loop.create_task(self.cycle.run_asgi(app), context=contextvars.Context())
+            else:  # pragma: no cover
+                task = contextvars.Context().run(self.loop.create_task, self.cycle.run_asgi(app))
             task.add_done_callback(self.tasks.discard)
             self.tasks.add(task)
         else: