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Parametrizing a test with an empty list calls ids callback with the private constant NOTSET #13031

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mon opened this issue Dec 6, 2024 · 6 comments · May be fixed by #13073
Open

Parametrizing a test with an empty list calls ids callback with the private constant NOTSET #13031

mon opened this issue Dec 6, 2024 · 6 comments · May be fixed by #13073

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@mon
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mon commented Dec 6, 2024

I parametrize tests based on a user-provided list. Sometimes this list is empty, which disables some tests as a result. However, I would expect the ids callback that I provide to not be called at all in that case, but it is actually called with the private NOTSET sentinel. As this is not exported, I can't easily check for it in my ids function and return a useless value to match it.

Reproduction:

conftest.py

import logging

def idmap(obj):
    logging.info(obj)

def pytest_generate_tests(metafunc):
    if "arg" in metafunc.fixturenames:
        metafunc.parametrize(
            "arg", [], ids=idmap
        )

test_demo.py

def test_demo(arg):
    pass
$: pytest --collect-only --log-cli-level=DEBUG
...
INFO     root:conftest.py:4 NotSetType.token
...

Python: 3.10.15
pytest: 8.3.4
OS: macOS Sonoma 14.6.1
@RonnyPfannschmidt
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For empty id lists we generate a single test with a warning

@mon
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mon commented Dec 6, 2024

Yes, which is reasonable - but I can't detect this in my ID mapping function because it's a hidden type. Perhaps the sentinel can just be exported? Or don't call the ID map for the "no parametrization" case.

I can make a PR in either case!

@RonnyPfannschmidt
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https://github.com/pytest-dev/pytest/blob/main/src%2F_pytest%2Fmark%2Fstructures.py#L182-L186

@mon
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mon commented Dec 6, 2024

I don't quite understand - I don't get access to the ParameterSet, and thus can't see its marks. I simply get NOTSET passed to the ids callback. Because NOTSET is internal to Pytest, I cannot compare the arg against it nor type annotate my ids function to accept it.

@RonnyPfannschmidt
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indeed - we should use a string that indicates it

@RonnyPfannschmidt
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i have a wip pr that sets the string NOTSET as direct id to avoid this - 'll polish it a litlle and push

RonnyPfannschmidt added a commit to RonnyPfannschmidt/pytest that referenced this issue Dec 17, 2024
@RonnyPfannschmidt
fix pytest-dev#13031: use the concrete id NOTSET for the empty parame…
c87c874 
…ter list stand-in

this ensures we dont invoke idfunc with the internal NOTSET enum token
@RonnyPfannschmidt RonnyPfannschmidt linked a pull request Dec 17, 2024 that will close this issue
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RonnyPfannschmidt added a commit to RonnyPfannschmidt/pytest that referenced this issue Dec 18, 2024
@RonnyPfannschmidt
fix pytest-dev#13031: use the concrete id NOTSET for the empty parame…
da7251c 
…ter list stand-in

this ensures we dont invoke idfunc with the internal NOTSET enum token
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fix #13031: use the concrete id NOTSET for the empty parameter list RonnyPfannschmidt/pytest
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@RonnyPfannschmidt @mon