Skip to content

gh-155433: Fix TaskGroup losing outside cancellation after cancel() #155439

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
kumaraditya303 merged 3 commits into from
Aug 23, 2026
Merged

gh-155433: Fix TaskGroup losing outside cancellation after cancel() #155439

Show file tree
Hide file tree
Changes from 2 commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
3b776cf
gh-155433: Fix TaskGroup losing outside cancellation after cancel()
deadlovelll Aug 9, 2026
131b0b8
propagate the original CancelledError
deadlovelll Aug 19, 2026
8f4049a
review changes
deadlovelll Aug 20, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions Lib/asyncio/taskgroups.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -116,13 +116,15 @@ async def _aexit(self, et, exc):
# can be cancelled multiple times if our parent task
# is being cancelled repeatedly (or even once, when
# our own cancellation is already in progress)
pending_cancellation_error = None
while self._tasks:
if self._on_completed_fut is None:
self._on_completed_fut = self._loop.create_future()

try:
await self._on_completed_fut
except exceptions.CancelledError as ex:
pending_cancellation_error = ex
if not self._aborting:
# Our parent task is being cancelled:
#
Expand Down Expand Up @@ -151,6 +153,9 @@ async def _aexit(self, et, exc):
# If there are no pending cancellations left,
# don't propagate CancelledError.
propagate_cancellation_error = None
elif propagate_cancellation_error is None:
# gh-155433: the remaining cancellation is not ours, don't drop it
propagate_cancellation_error = pending_cancellation_error

# Propagate CancelledError if there is one, except if there
# are other errors -- those have priority.
Expand Down
20 changes: 20 additions & 0 deletions Lib/test/test_asyncio/test_taskgroups.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1154,6 +1154,26 @@ async def test_taskgroup_cancel_before_create_task(self):
with self.assertRaises(RuntimeError):
tg.create_task(asyncio.sleep(1))

async def test_taskgroup_cancel_keeps_outer_cancellation(self):
# gh-155433: any cancellation from outside the group must propagate.
async def child():
try:
await asyncio.sleep(10)
finally:
await asyncio.sleep(0.1)

async def body():
async with asyncio.TaskGroup() as tg:
tg.create_task(child())
await asyncio.sleep(0)
tg.cancel()

task = asyncio.create_task(body())
await asyncio.sleep(0.01)
task.cancel()
with self.assertRaises(asyncio.CancelledError):
await task
Comment thread
kumaraditya303 marked this conversation as resolved.
Resolved

async def test_taskgroup_cancel_before_exception(self):
async def raise_exc(parent_tg: asyncio.TaskGroup):
parent_tg.cancel()
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2026-08-09-16-14-38.gh-issue-155433.KL7tHV.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Fix :class:`asyncio.TaskGroup` losing outside cancellation after
``cancel()``.
Loading