[issue26552] Failing ensure_future still creates a Task

[Guido van Rossum]

Guido van Rossum  added the comment:


New changeset a5451c96a14ac0c3ee7cef7b5c52ab1d783ec613 by Kumar Aditya in 
branch '3.10':
bpo-26552: Fixed case where failing `asyncio.ensure_future` did not close the 
coroutine (#30288) (#31003)
https://github.com/python/cpython/commit/a5451c96a14ac0c3ee7cef7b5c52ab1d783ec613


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[issue26552] Failing ensure_future still creates a Task

[Kumar Aditya]

Change by Kumar Aditya :


--
pull_requests: +29185
pull_request: https://github.com/python/cpython/pull/31003

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[issue26552] Failing ensure_future still creates a Task

[Guido van Rossum]

Guido van Rossum  added the comment:

Thanks Kumar for the fix!

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resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue26552] Failing ensure_future still creates a Task

[Guido van Rossum]

Guido van Rossum  added the comment:


New changeset 24cc6411adbfeecd8901f1ea50caa414c908 by Kumar Aditya in 
branch 'main':
bpo-26552: Fixed case where failing `asyncio.ensure_future` did not close the 
coroutine (#30288)
https://github.com/python/cpython/commit/24cc6411adbfeecd8901f1ea50caa414c908


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[issue26552] Failing ensure_future still creates a Task

[Guido van Rossum]

Guido van Rossum  added the comment:

So I just realized that the OP's description is slightly misleading. (Their 
code is spot on though!)

The code does not create an unwaited-for *task*, assuming that "task" refers to 
the asyncio.Task class.

What is created is a *coroutine* object that's never awaited (as the quoted 
RuntimeWarning message says: "coroutine 'foo' was never awaited").

So the thing that needs to be closed in the bowels of _ensure_future() is 
indeed the argument (coro_or_future), in case it is a coroutine object.

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[issue26552] Failing ensure_future still creates a Task

[Kumar Aditya]

Change by Kumar Aditya :


--
nosy: +kumaraditya303
nosy_count: 5.0 -> 6.0
pull_requests: +28502
pull_request: https://github.com/python/cpython/pull/30288

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[issue26552] Failing ensure_future still creates a Task

[Carlos Damázio]

Change by Carlos Damázio :


--
keywords: +patch
nosy: +dmzz
nosy_count: 4.0 -> 5.0
pull_requests: +28501
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/30287

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[issue26552] Failing ensure_future still creates a Task

[Guido van Rossum]

Change by Guido van Rossum :


--
keywords: +easy

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[issue26552] Failing ensure_future still creates a Task

[STINNER Victor]

Change by STINNER Victor :


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nosy:  -vstinner

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[issue26552] Failing ensure_future still creates a Task

[Irit Katriel]

Irit Katriel  added the comment:

Reproduced on 3.11.

--
nosy: +iritkatriel
versions: +Python 3.10, Python 3.11, Python 3.9 -Python 3.5

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[issue26552] Failing ensure_future still creates a Task

[Guido van Rossum]

Guido van Rossum added the comment:

Sounds like an easy fix. Could you submit a patch?

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[issue26552] Failing ensure_future still creates a Task

[Damien Nicolas]

New submission from Damien Nicolas:

When calling asyncio.ensure_future() on a coroutine, and if the loop is closed, 
ensure_future() will raise a RuntimeError. 

However, it still creates a Task, which will generate a RuntimeWarning that we 
can’t fix since there is no way to cancel the Task.

Here is the code to reproduce the bug:


import asyncio

l = asyncio.get_event_loop()
l.close()

async def foo():
pass

try:
# Since the exception raises here, fut is never set
# so we can't call fut.cancel()
fut = asyncio.ensure_future(foo())
except RuntimeError:
pass


# stderr:
# aio.py:12: RuntimeWarning: coroutine 'foo' was never awaited
#   pass

--
components: asyncio
messages: 261696
nosy: gordon, gvanrossum, haypo, yselivanov
priority: normal
severity: normal
status: open
title: Failing ensure_future still creates a Task
type: behavior
versions: Python 3.5

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