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WarningsRecorder.pop() improperly matches warning #10701

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#11160
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WarningsRecorder.pop() improperly matches warning#10701
#11160
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good first issueeasy issue that is friendly to new contributorplugin: warningsrelated to the warnings builtin plugintype: enhancementnew feature or API change, should be merged into features branch
@groutr

Description

@groutr
groutr
opened on Feb 2, 2023

When trying to pop a specific warning from a WarningsRecorder instance, the wrong warning is returned. I believe the issue is that pop uses issubclass

pytest/src/_pytest/recwarn.py

Line 210 in 3c15349

if issubclass(w.category, cls):

I believe the correct comparison should be:

if w.category is cls:

Here is a minimum working example that triggers the buggy behavior:

import pytest
import warnings

class RWarning(Warning):
    pass
    
class SWarning(RWarning):
    pass

def raise_warnings():
    warnings.warn("Warning 1", SWarning)
    warnings.warn("Warning 2", RWarning)
    
def test_pop():
    with pytest.warns((RWarning, SWarning)) as record:
        raise_warnings()
        
    assert len(record) == 2
    _warn = record.pop(RWarning)
    assert _warn.category is RWarning  # This fails because _warn.category is SWarning

The test output is

========================================================================================= FAILURES ==========================================================================================
_________________________________________________________________________________________ test_pop __________________________________________________________________________________________

    def test_pop():
        with pytest.warns((RWarning, SWarning)) as record:
            raise_warnings()

        assert len(record) == 2
        _warn = record.pop(RWarning)
>       assert _warn.category is RWarning
E       AssertionError: assert <class 'pytest_bug.SWarning'> is RWarning
E        +  where <class 'pytest_bug.SWarning'> = <warnings.WarningMessage object at 0x7fea08a72010>.category

pytest_bug.py:24: AssertionError

pytest 7.2.1 on archlinux.
virtual environment is a clean conda environment with only python and pytest (and their dependencies installed from conda-forge).

If this is indeed a bug, I'm happy to open a PR with my proposed solution.

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    good first issueeasy issue that is friendly to new contributorplugin: warningsrelated to the warnings builtin plugintype: enhancementnew feature or API change, should be merged into features branch

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