[New-bugs-announce] [issue30048] If a task is canceled at the right moment, the cancellation is ignored

[Evgeny Kapun]

New submission from Evgeny Kapun:

If I run this code:

    import asyncio as a

    @a.coroutine
    def coro1():
        yield from a.ensure_future(coro2())
        print("Still here")
        yield from a.sleep(1)
        print("Still here 2")

    @a.coroutine
    def coro2():
        yield from a.sleep(1)
        res = task.cancel()
        print("Canceled task:", res)

    loop = a.get_event_loop()
    task = a.ensure_future(coro1())
    loop.run_until_complete(task)

I expect the task to stop shortly after a call to cancel(). It should surely stop when I try to sleep(). But it doesn't. On my machine this prints:

    Canceled task: True
    Still here
    Still here 2

So, cancel() returns True, but the task doesn't seem to be canceled.

----------
components: asyncio
messages: 291522
nosy: abacabadabacaba, yselivanov
priority: normal
severity: normal
status: open
title: If a task is canceled at the right moment, the cancellation is ignored
type: behavior
versions: Python 3.5, Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue30048>
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