Kyle Stanley <aeros...@gmail.com> added the comment:
Upon further investigation, I've realized that the issue is just that the cancel() override for `_GatheringFuture` never sets its state to CANCELLED at any point (unlike its parent), and is instead going to always be set to FINISHED because of the `outer.set_exception()` (https://github.com/python/cpython/blob/b8f67c0923ac85468dfbfd43375e0bbfb6ca50ea/Lib/asyncio/tasks.py#L826 or https://github.com/python/cpython/blob/b8f67c0923ac85468dfbfd43375e0bbfb6ca50ea/Lib/asyncio/tasks.py#L791, depending on the arg for *return_exceptions*). Since we are unable to set the state of `_GatheringFuture` (at least not without causing side effects), I'm starting to agree that it makes sense to override the behavior for `cancelled()`. However, it might make more sense to replace the `self._cancel_requested` check with `isinstance(self.exception(), exceptions.CancelledError)`, as this more accurately indicates if and when the gather() was cancelled. I don't think we should rely on `self._cancel_requested` since it would be true before the future is actually cancelled and not always be correct since the gather() can be cancelled without setting `self._cancel_requested`. Here's one case where relying on `self._cancel_requested` for future_gather.cancelled() wouldn't work, based on a slight modification of the reproducer example: ``` async def main(): """Cancel a gather() future and child and return it.""" task_child = ensure_future(sleep(1.0)) future_gather = gather(task_child) task_child.cancel() try: await future_gather except asyncio.CancelledError: pass return future_gather, task_child ``` (Despite `await future_gather` raising a CancelError and effectively being cancelled, `future_gather.cancelled()` would return false since `self._cancel_requested` was never set to true.) ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue40894> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
