Added a comment about the use of futures.CancelledError

homeassistant/components/websocket_api.py

@@ -5,8 +5,8 @@
 https://home-assistant.io/developers/websocket_api/
 """
 import asyncio
+from concurrent import futures
 from contextlib import suppress
-from concurrent.futures import CancelledError
 from functools import partial
 import json
 import logging
@@ -121,6 +121,11 @@
                                   TYPE_PING)
 }, extra=vol.ALLOW_EXTRA)
 
+# Define the possible errors that occur when connections are cancelled.
+# Originally, this was just asyncio.CancelledError, but issue #9546 showed
+# that futures.CancelledErrors can also occur in some situations.
+CANCELLATION_ERRORS = (asyncio.CancelledError, futures.CancelledError)
+
 
 def auth_ok_message():
     """Return an auth_ok message."""
@@ -232,7 +237,7 @@ def log_error(self, message1, message2=''):
     def _writer(self):
         """Write outgoing messages."""
         # Exceptions if Socket disconnected or cancelled by connection handler
-        with suppress(RuntimeError, asyncio.CancelledError, CancelledError):
+        with suppress(RuntimeError, *CANCELLATION_ERRORS):
             while not self.wsock.closed:
                 message = yield from self.to_write.get()
                 if message is None:
@@ -364,7 +369,7 @@ def handle_hass_stop(event):
             self.log_error(msg)
             self._writer_task.cancel()
 
-        except (asyncio.CancelledError, CancelledError):
+        except CANCELLATION_ERRORS:
             self.debug("Connection cancelled by server")
 
         except asyncio.QueueFull: