https://github.com/python/cpython/commit/fbd2e015d462870b9a48bb5e6628af6c372ed1d5
commit: fbd2e015d462870b9a48bb5e6628af6c372ed1d5
branch: main
author: Andrew Geng <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2026-08-15T04:26:32Z
summary:
gh-155143: Fix asyncio.shield() leaking tasks via await-graph (#155144)
files:
A Misc/NEWS.d/next/Library/2026-08-03-22-46-07.gh-issue-155143.9-byZp.rst
M Lib/asyncio/tasks.py
M Lib/test/test_asyncio/test_tasks.py
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index 9d20930dc300c67..7889d4793a5dec3 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -997,6 +997,9 @@ def _outer_done_callback(outer):
# Keep only one callback to log on cancel
inner.remove_done_callback(_log_on_exception)
inner.add_done_callback(_log_on_exception)
+ if cur_task is not None:
+ inner.remove_done_callback(_clear_awaited_by_callback)
+ futures.future_discard_from_awaited_by(inner, cur_task)
if cur_task is not None:
inner.add_done_callback(_clear_awaited_by_callback)
diff --git a/Lib/test/test_asyncio/test_tasks.py
b/Lib/test/test_asyncio/test_tasks.py
index ad9b09857f8fd2b..9c111da8c27f162 100644
--- a/Lib/test/test_asyncio/test_tasks.py
+++ b/Lib/test/test_asyncio/test_tasks.py
@@ -2109,6 +2109,8 @@ def test_shield_cancel_outer(self):
test_utils.run_briefly(self.loop)
self.assertTrue(outer.cancelled())
self.assertEqual(0, 0 if outer._callbacks is None else
len(outer._callbacks))
+ self.assertFalse(inner._asyncio_awaited_by)
+ self.assertTrue({f for f, _ctx in inner._callbacks or []} <=
{asyncio.tasks._log_on_exception})
def test_shield_cancel_outer_result(self):
mock_handler = mock.Mock()
@@ -2134,6 +2136,21 @@ def test_shield_cancel_outer_exception(self):
test_utils.run_briefly(self.loop)
mock_handler.assert_called_once()
+ def test_shield_cancel_outer_in_task(self):
+ inner = self.new_future(self.loop)
+
+ async def coro():
+ outer = asyncio.shield(inner)
+ self.assertNotEqual(0, len(inner._callbacks))
+ outer.cancel()
+ await asyncio.sleep(0)
+ self.assertTrue(outer.cancelled())
+
+ task = self.new_task(self.loop, coro())
+ self.loop.run_until_complete(task)
+ self.assertFalse(inner._asyncio_awaited_by)
+ self.assertTrue({f for f, _ctx in inner._callbacks or []} <=
{asyncio.tasks._log_on_exception})
+
def test_shield_duplicate_log_once(self):
mock_handler = mock.Mock()
self.loop.set_exception_handler(mock_handler)
diff --git
a/Misc/NEWS.d/next/Library/2026-08-03-22-46-07.gh-issue-155143.9-byZp.rst
b/Misc/NEWS.d/next/Library/2026-08-03-22-46-07.gh-issue-155143.9-byZp.rst
new file mode 100644
index 000000000000000..ae39b30e40a643e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-08-03-22-46-07.gh-issue-155143.9-byZp.rst
@@ -0,0 +1,2 @@
+Fix :func:`asyncio.shield` leaking the calling task via the await-graph and
+callbacks when called on a future that never resolves.
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