[New-bugs-announce] [issue34074] Asyncio breaks coroutine finalization process

[Andriy Maletsky]

New submission from Andriy Maletsky <andriy.maletsky at gmail.com>:

Source: https://stackoverflow.com/q/51245011/6275324

Asyncio somehow breaks coroutine finalization. I believe there may be a bug in C implementation (_asyncio) of tasks or futures. Reproducible within version 3.7.0 at python:3.7 docker container.

Consider this example (except and finally blocks will never execute):


import asyncio

async def work():
    try:
        print('started working')
        await asyncio.sleep(3600)
    except BaseException as e:
        print('caught ' + str(type(e)))
    finally:
        print('finalization completed')

async def stopper():
    await asyncio.sleep(5)
    loop.stop()

loop = asyncio.get_event_loop()
loop.create_task(work())
loop.create_task(stopper())
loop.run_forever()



And there is asyncio-free piece of code, which works properly, catching GeneratorExit, thrown by coro destructor:


import asyncio

async def work():
    try:
        print('started working')
        await asyncio.sleep(3600)
    except BaseException as e:
        print('caught ' + str(type(e)))
    finally:
        print('finalization completed')

coro = work()
coro.send(None)
del coro

----------
components: asyncio
messages: 321321
nosy: and800, asvetlov, yselivanov
priority: normal
severity: normal
status: open
title: Asyncio breaks coroutine finalization process
type: behavior
versions: Python 3.6, Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue34074>
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