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IsolatedAsyncioTestCase freezes when exception is raised #83282

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fornellas mannequin opened this issue Dec 19, 2019 · 5 comments
Closed

IsolatedAsyncioTestCase freezes when exception is raised #83282

fornellas mannequin opened this issue Dec 19, 2019 · 5 comments
Labels
3.8 only security fixes topic-asyncio type-crash A hard crash of the interpreter, possibly with a core dump

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@fornellas
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Mannequin

fornellas mannequin commented Dec 19, 2019

BPO 39101
Nosy @asvetlov, @1st1, @lisroach, @miss-islington, @fornellas, @r-owen
PRs
  • bpo-39101: Fixes BaseException hang in IsolatedAsyncioTestCase. #22654
  • [3.9] bpo-39101: Fixes BaseException hang in IsolatedAsyncioTestCase. (GH-22654) #22988
  • [3.8] bpo-39101: Fixes BaseException hang in IsolatedAsyncioTestCase. (GH-22654) #22989
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
closed_at = <Date 2020-10-26.16:29:40.338>
created_at = <Date 2019-12-19.19:44:59.009>
labels = ['3.8', 'type-crash', 'expert-asyncio']
title = 'IsolatedAsyncioTestCase freezes when exception is raised'
updated_at = <Date 2021-03-02.00:30:08.714>
user = 'https://github.com/fornellas'

    bugs.python.org fields:

    activity = <Date 2021-03-02.00:30:08.714>
actor = 'r3owen'
assignee = 'none'
closed = True
closed_date = <Date 2020-10-26.16:29:40.338>
closer = 'lisroach'
components = ['asyncio']
creation = <Date 2019-12-19.19:44:59.009>
creator = 'fornellas'
dependencies = []
files = []
hgrepos = []
issue_num = 39101
keywords = ['patch']
message_count = 5.0
messages = ['358690', '379670', '383195', '383196', '387887']
nosy_count = 6.0
nosy_names = ['asvetlov', 'yselivanov', 'lisroach', 'miss-islington', 'fornellas', 'r3owen']
pr_nums = ['22654', '22988', '22989']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue39101'
versions = ['Python 3.8']
    @fornellas
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    fornellas mannequin commented Dec 19, 2019

    IsolatedAsyncioTestCase freezes whenever an exception that inherits from BaseException is raised:

    import unittest
class TestHangsForever(unittest.IsolatedAsyncioTestCase):
    async def test_hangs_forever(self):
        raise BaseException("Hangs forever")
if __name__ == "__main__":
    import unittest
    unittest.main()

    A kind of similar issue present on 3.7 was fixed on 3.8 here https://github.com/python/cpython/blob/3.8/Lib/asyncio/events.py#L84, where BaseExceptions would not be correctly handled by the event loop, this seems somewhat related.

    I had a look at IsolatedAsyncioTestCase implementation, did not spot any obvious broken thing there, I could use some light here. Thanks.

    @fornellas fornellas mannequin added 3.8 only security fixes topic-asyncio type-crash A hard crash of the interpreter, possibly with a core dump labels Dec 19, 2019
    @lisroach
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    New changeset 8374d2e by Lisa Roach in branch 'master':
    bpo-39101: Fixes BaseException hang in IsolatedAsyncioTestCase. (GH-22654)
    8374d2e

    @miss-islington
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    New changeset 9d409d6 by Miss Islington (bot) in branch '3.9':
    bpo-39101: Fixes BaseException hang in IsolatedAsyncioTestCase. (GH-22654)
    9d409d6

    @miss-islington
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    New changeset d549d0b by Miss Islington (bot) in branch '3.8':
    bpo-39101: Fixes BaseException hang in IsolatedAsyncioTestCase. (GH-22654)
    d549d0b

    @r-owen
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    r-owen mannequin commented Mar 2, 2021

    Here is a variant that also hangs, I suspect for the same reason. The task raises asyncio.CancelledError which inherits from BaseException and my guess is it somehow kills the event loop.

    import asyncio
import unittest


class DemonstrateHang(unittest.IsolatedAsyncioTestCase):
    async def test_hang(self):
        task = asyncio.create_task(asyncio.sleep(2))
        await asyncio.sleep(0.1)
        task.cancel()
        await task
        # this also hangs: await asyncio.wait_for(task, 5)

    @ezio-melotti ezio-melotti transferred this issue from another repository Apr 10, 2022
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