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Pytest reevaluates walrus operations within assert statements #11115

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  • a detailed description of the bug or problem you are having
  • output of pip list from the virtual environment you are using
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Ubuntu 22.04, pytest 7.3.2, python 3.10.11

Package Version


exceptiongroup 1.1.1
iniconfig 2.0.0
packaging 23.1
pip 23.1.2
pluggy 1.0.0
pytest 7.3.2
setuptools 67.8.0
tomli 2.0.1
wheel 0.38.4

Pytest 7.3.2 re-evaluates walrus operator statements if they appear in assert statements.

def test_walrus():
    assert (x := 2) == 2
    x  =  3
    assert x == 3, "This test fails because (x := 2) is reevaluated by pytest"
    
def test_walrus_no_assert():
    (x := 2) == 2
    x = 3
    assert x == 3, "This test passes because (x := 2) is not reevaluated"

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    topic: rewriterelated to the assertion rewrite mechanismtype: regressionindicates a problem that was introduced in a release which was working previously

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