Adam Liddell added the comment:
Wrapping every resource allocating call like that is what we were trying to
avoid, since it makes wait_for go from a simple one-line helper to something
you have to be very careful with.
Conceptually, a user should expect that wait_for should behave the exact same
as awaiting the underlying awaitable, just with auto-cancellation. The problem
with the current wait_for is that there is a gap where the underlying task may
have completed but a cancellation arrives. In this case, we need to raise the
cancellation to be a good asyncio citizen, but the underlying task has no
opportunity to act on the cancellation (to free the resource) since it is
already complete and cannot be re-entered. So the resource returned by the
completed task gets stuck in limbo, since we can't return it and we can't
assume a generic 'close' behaviour.
See my comment in the PR for a suggestion about an alternative structure for
wait_for, which may avoid this gap and hence prevent the leak (but I have not
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