From 448d0703860ebc28d1fdcd92bc97a5477d805a67 Mon Sep 17 00:00:00 2001 From: mohsinm-dev Date: Sat, 8 Nov 2025 19:28:29 +0500 Subject: [PATCH] gh-141186: Document asyncio Task cancellation propagation behavior Clarifies that cancelling a Task awaiting another Task or Future will also cancel the awaited object. This behavior was undocumented despite being fundamental to asyncio's cancellation architecture. Changes: - Updated general Task description to mention Task cancellation propagation - Added explicit explanation in Task.cancel() method documentation - Clarified that Tasks inherit Future's cancellation behavior Addresses issue #141186 where users were unaware this cancellation propagation was intentional architectural behavior, not a side effect. The fix uses the exact wording suggested by the issue reporter and documents the _fut_waiter implementation behavior that enables the propagation down entire await chains. --- Doc/library/asyncio-task.rst | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/Doc/library/asyncio-task.rst b/Doc/library/asyncio-task.rst index f825ae92ec7471..863b3e336572aa 100644 --- a/Doc/library/asyncio-task.rst +++ b/Doc/library/asyncio-task.rst @@ -1221,8 +1221,8 @@ Task Object To cancel a running Task use the :meth:`cancel` method. Calling it will cause the Task to throw a :exc:`CancelledError` exception into - the wrapped coroutine. If a coroutine is awaiting on a Future - object during cancellation, the Future object will be cancelled. + the wrapped coroutine. If a coroutine is awaiting on a future-like + object during cancellation, the awaited object will be cancelled. :meth:`cancelled` can be used to check if the Task was cancelled. The method returns ``True`` if the wrapped coroutine did not @@ -1411,6 +1411,10 @@ Task Object the cancellation, it needs to call :meth:`Task.uncancel` in addition to catching the exception. + If the Task being cancelled is currently awaiting on a future-like + object, that awaited object will also be cancelled. This cancellation + propagates down the entire chain of awaited objects. + .. versionchanged:: 3.9 Added the *msg* parameter.