I'm still not sure if the explicit "and exits the group without raising :exc:asyncio.CancelledError" makes sense. All this does is 1) cancel all current tasks in the group and 2) set the task group into aborted mode which causes creation of further tasks to fail. With that in mind, I'm not sure why you chose to explicitly mention exiting the task group.

Further, this still begs to question why you said "without raising :exc:asyncio.CancelledError". This implies that otherwise it would raise a CancelledError, yes?

well, if you check the long discussions in the impl PR, there was quite a bit made about possible confusion from expecting TaskGroup.cancel() to behave like Task.cancel(). So this is being explicit that unlike the latter, TaskGroup.cancel() does not cause anything to raise CancelledError.

I think this could be reworded:

Add :meth:~asyncio.TaskGroup.cancel which cancels unfinished tasks in the group and prevents new ones from being created. If this requires cancellation of the host task, the task group will swallow the :exc:asyncio.CancelledError, unless the task was also cancelled from elsewhere.

Thoughts?