asyncio: Improve canceled timer handles cleanup. Closes issue #22448.

Patch by Joshua Moore-Oliva.

1 files changed, 20 insertions, 9 deletions

diff --git a/Lib/asyncio/events.py b/Lib/asyncio/events.py
index b7cc351..806218f 100644
--- a/Lib/asyncio/events.py
+++ b/Lib/asyncio/events.py
@@ -105,14 +105,15 @@ class Handle:
         return '<%s>' % ' '.join(info)
 
     def cancel(self):
-        self._cancelled = True
-        if self._loop.get_debug():
-            # Keep a representation in debug mode to keep callback and
-            # parameters. For example, to log the warning "Executing <Handle
-            # ...> took 2.5 second"
-            self._repr = repr(self)
-        self._callback = None
-        self._args = None
+        if not self._cancelled:
+            self._cancelled = True
+            if self._loop.get_debug():
+                # Keep a representation in debug mode to keep callback and
+                # parameters. For example, to log the warning
+                # "Executing <Handle...> took 2.5 second"
+                self._repr = repr(self)
+            self._callback = None
+            self._args = None
 
     def _run(self):
         try:
@@ -134,7 +135,7 @@ class Handle:
 class TimerHandle(Handle):
     """Object returned by timed callback registration methods."""
 
-    __slots__ = ['_when']
+    __slots__ = ['_scheduled', '_when']
 
     def __init__(self, when, callback, args, loop):
         assert when is not None
@@ -142,6 +143,7 @@ class TimerHandle(Handle):
         if self._source_traceback:
             del self._source_traceback[-1]
         self._when = when
+        self._scheduled = False
 
     def _repr_info(self):
         info = super()._repr_info()
@@ -180,6 +182,11 @@ class TimerHandle(Handle):
         equal = self.__eq__(other)
         return NotImplemented if equal is NotImplemented else not equal
 
+    def cancel(self):
+        if not self._cancelled:
+            self._loop._timer_handle_cancelled(self)
+        super().cancel()
+
 
 class AbstractServer:
     """Abstract server returned by create_server()."""
@@ -238,6 +245,10 @@ class AbstractEventLoop:
 
     # Methods scheduling callbacks.  All these return Handles.
 
+    def _timer_handle_cancelled(self, handle):
+        """Notification that a TimerHandle has been cancelled."""
+        raise NotImplementedError
+
     def call_soon(self, callback, *args):
         return self.call_later(0, callback, *args)