asyncio.Timeout raises AttributeError when not used in loop

[Gobot1234]

Bug report

Bug description:

    async def __aenter__(self) -> "Timeout":
        self._state = _State.ENTERED
        self._task = tasks.current_task()
        self._cancelling = self._task.cancelling()  # AttributeError
        if self._task is None:
            raise RuntimeError("Timeout should be used inside a task")
        self.reschedule(self._when)
        return self

Honestly I don't know how to get this to error but it's possible according to the types

CPython versions tested on:

3.13, CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-111085 Fix logic order causing nicer error to never be raised in asyncio.Timeout #110910
• gh-111085: Fix invalid state handling in TaskGroup and Timeout #111111
• [3.12] gh-111085: Fix invalid state handling in TaskGroup and Timeout (GH-111111) #111171
• [3.11] gh-111085: Fix invalid state handling in TaskGroup and Timeout (GH-111111) #111172

[gvanrossum]

What is the bug? You just posted some code, I am missing context for that code.

[Gobot1234]

It accesses self._task while it could still be None before the is None check

[gvanrossum]

Got it. Do you want to send a PR?

[Gobot1234]

The PR is already sent :)

[gvanrossum]

Oh wait. You started with the PR. A bit unconventional. :-)

I don’t think I am needed here.

[serhiy-storchaka]

The problem is larger and more complex than it looked. It applies as well to TaskGroup.

• The valid state is not always checked.
• If it is checked, sometimes assert is used for this, even if the condition can be false.
• If an exception is raised, it can left the object in inconsistent state which breaks checks in the following operations.

It was also not trivial to write tests for this. So I created a new PR #111111.