bpo-35125: remove inner callback on outer cancellation in asyncio shield (GH-10340)
When the future returned by shield is cancelled, its completion callback of the
inner future is not removed. This makes the callback list of inner inner future
grow each time a shield is created and cancelled.
This change unregisters the callback from the inner future when the outer
future is cancelled.
https://bugs.python.org/issue35125
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index b007b74..211b912 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -818,7 +818,7 @@
loop = futures._get_loop(inner)
outer = loop.create_future()
- def _done_callback(inner):
+ def _inner_done_callback(inner):
if outer.cancelled():
if not inner.cancelled():
# Mark inner's result as retrieved.
@@ -834,7 +834,13 @@
else:
outer.set_result(inner.result())
- inner.add_done_callback(_done_callback)
+
+ def _outer_done_callback(outer):
+ if not inner.done():
+ inner.remove_done_callback(_inner_done_callback)
+
+ inner.add_done_callback(_inner_done_callback)
+ outer.add_done_callback(_outer_done_callback)
return outer