gh-113538: Allow client connections to be closed

Doc/library/asyncio-eventloop.rst

@@ -1648,6 +1648,9 @@ Do not instantiate the :class:`Server` class directly.
       Calls :meth:`~asyncio.BaseTransport.close` on all associated
       transports.
 
+      :meth:`close` should be called before :meth:`close_clients` when
+      closing the server to avoid races with new clients connecting.
+
       .. versionadded:: 3.13
 
    .. method:: abort_clients()
@@ -1658,6 +1661,9 @@ Do not instantiate the :class:`Server` class directly.
       Calls :meth:`~asyncio.WriteTransport.abort` on all associated
       transports.
 
+      :meth:`close` should be called before :meth:`abort_clients` when
+      closing the server to avoid races with new clients connecting.
+
       .. versionadded:: 3.13
 
    .. method:: get_loop()

Doc/whatsnew/3.13.rst

@@ -169,7 +169,7 @@ asyncio
   (Contributed by Pierre Ossman in :gh:`111246`.)
 
 * Add :meth:`asyncio.Server.close_clients` and
-  :meth:`asyncio.Server.abort_clients` methods which allows to more
+  :meth:`asyncio.Server.abort_clients` methods which allow to more
   forcefully close an asyncio server.
   (Contributed by Pierre Ossman in :gh:`113538`.)
 

Lib/asyncio/base_events.py

@@ -298,8 +298,7 @@ def _attach(self, transport):
     def _detach(self, transport):
         # Note that 'transport' may already be missing from
         # self._clients if it has been garbage collected
-        if transport in self._clients:
-            self._clients.remove(transport)
+        self._clients.discard(transport)
         if len(self._clients) == 0 and self._sockets is None:
             self._wakeup()
 

Misc/NEWS.d/next/Library/2024-01-22-15-50-58.gh-issue-113538.v2wrwg.rst

@@ -1,3 +1,3 @@
 Add :meth:`asyncio.Server.close_clients` and
-:meth:`asyncio.Server.abort_clients` methods which allows to more forcefully
+:meth:`asyncio.Server.abort_clients` methods which allow to more forcefully
 close an asyncio server.