GeezerVison

Hi,
I ran this code with your changes, for the required test in the 'externally cancel' case.
Here a CancelledError is raised, _parent_cancel_requested is False, so uncancel() is never called. Is the expected behavior ?

import asyncio

class MyException(Exception):
    pass

async def async_fn2():
    try:
        await asyncio.sleep(0.0)
        raise MyException
    finally:
        print("raise done")

async def main():
    task = asyncio.current_task()
    try:
        async with asyncio.TaskGroup() as tg:
            tg.create_task(async_fn2())
            await asyncio.sleep(1)

    except* (MyException, asyncio.CancelledError) as e:
        # How to check a private `_parent_cancel_requested` attr here, outside the class ?
        print(f"{e.exceptions} -> {task.cancelling()=}, {tg._parent_cancel_requested=}")

async def supermain():
    t = asyncio.create_task(main())
    await asyncio.sleep(0)

    t.cancel()
    print("cancel main task")
    await asyncio.sleep(1)

    print(f"{t.cancelling()=} must be 1, confirm ?")

asyncio.run(supermain())

That code looks racy with the sleep(0.0) calls, but it is correct that since your supermain code cancels main, uncancel will not be called. Note that _parent_cancel_requested is not truly private (single underscore) so for debugging can check it.

I wonder whether it is important to check if parent task is not cancelling when starts the async with ?
In that case, should we raise a RuntimeError in the __aenter__ ?

I wonder whether it is important to check if parent task is not cancelling when starts the async with ? In that case, should we raise a RuntimeError in the __aenter__ ?

What problem would that solve?

I wonder whether it is important to check if parent task is not cancelling when starts the async with ? In that case, should we raise a RuntimeError in the aenter ?

What problem would that solve?

Problem is already solved with the 'externally cancel' case.
Sorry for waste your time.

Superseded by #95602 which includes tests.