https://github.com/python/cpython/commit/4b33a9db8084bb4a5c631db5cb97e4a2e0e33a98 commit: 4b33a9db8084bb4a5c631db5cb97e4a2e0e33a98 branch: main author: Pengyu Lee <[email protected]> committer: kumaraditya303 <[email protected]> date: 2026-10-20T12:31:15Z summary:
gh-158004: preserve `asyncio.as_completed()` items after anext cancellation (#158005) Co-authored-by: Kumar Aditya <[email protected]> files: A Misc/NEWS.d/next/Library/2026-09-23-19-59-03.gh-issue-158004.p68swW.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 1baa7518692d8a..6c8d7cbbda6440 100644 --- a/Lib/asyncio/tasks.py +++ b/Lib/asyncio/tasks.py @@ -636,7 +636,11 @@ async def _wait_for_one(self, resolve=False): # Wait for the next future to be done and return it unless resolve is # set, in which case return either the result of the future or raise # an exception. - f = await self._done.get() + try: + f = await self._done.get() + except: + self._todo_left += 1 + raise if f is None: # Dummy value from _handle_timeout(). raise exceptions.TimeoutError diff --git a/Lib/test/test_asyncio/test_tasks.py b/Lib/test/test_asyncio/test_tasks.py index c93e0e7b6a4004..7641c361f9666e 100644 --- a/Lib/test/test_asyncio/test_tasks.py +++ b/Lib/test/test_asyncio/test_tasks.py @@ -1702,6 +1702,46 @@ async def coro(i): ) self.assertCountEqual(results, (0, 1, 2, 3)) + def test_as_completed_async_iterator_cancelled_anext(self): + async def main(): + loop = asyncio.get_running_loop() + a = loop.create_future() + b = loop.create_future() + iterator = asyncio.as_completed([a, b]) + + waiter = asyncio.create_task(anext(iterator)) + await asyncio.sleep(0) + waiter.cancel() + with self.assertRaises(asyncio.CancelledError): + await waiter + + a.set_result('a') + b.set_result('b') + return [await f async for f in iterator] + + results = self.loop.run_until_complete(main()) + self.assertCountEqual(results, ['a', 'b']) + + def test_as_completed_plain_iterator_cancelled_wait(self): + async def main(): + loop = asyncio.get_running_loop() + a = loop.create_future() + b = loop.create_future() + iterator = asyncio.as_completed([a, b]) + + waiter = asyncio.create_task(next(iterator)) + await asyncio.sleep(0) + waiter.cancel() + with self.assertRaises(asyncio.CancelledError): + await waiter + + a.set_result('a') + b.set_result('b') + return [await c for c in iterator] + + results = self.loop.run_until_complete(main()) + self.assertCountEqual(results, ['a', 'b']) + def test_as_completed_reverse_wait(self): # Tests the plain iterator style of as_completed iteration to # ensure that the first future awaited resolves to the first diff --git a/Misc/NEWS.d/next/Library/2026-09-23-19-59-03.gh-issue-158004.p68swW.rst b/Misc/NEWS.d/next/Library/2026-09-23-19-59-03.gh-issue-158004.p68swW.rst new file mode 100644 index 00000000000000..0db4a3d4ca4c4a --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-09-23-19-59-03.gh-issue-158004.p68swW.rst @@ -0,0 +1,2 @@ +Fix :func:`asyncio.as_completed` to continue yielding every awaitable after +a pending iteration step is cancelled. _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
