[3.7] bpo-34872: Fix self-cancellation in C implementation of asyncio.Task (GH-9679) by elprans · Pull Request #9691 · python/cpython (original) (raw)

The C implementation of asyncio.Task currently fails to perform the
cancellation cleanup correctly in the following scenario.

async def task1():
    async def task2():
        await task3     # task3 is never cancelled

    asyncio.current_task().cancel()
    await asyncio.create_task(task2())

The actuall error is a hardcoded call to future_cancel() instead of
calling the cancel() method of a future-like object.

Thanks to Vladimir Matveev for noticing the code discrepancy and to
Yury Selivanov for coming up with a pathological scenario..
(cherry picked from commit 548ce9d)

Co-authored-by: Elvis Pranskevichus elvis@magic.io

https://bugs.python.org/issue34872