F823 false positive

[bastimeyer]

$ ruff -V
ruff 0.0.280

Consider the following code snippet which overrides the default requests_mock pytest fixture with InvalidRequest being raised on unknown requests, so it needs to import the requests_mock package with the same name first in order to access certain exports like Mocker, ANY, or the exceptions submodule:

import pytest
import requests_mock as rm

@pytest.fixture()
def requests_mock(requests_mock: rm.Mocker) -> rm.Mocker:
    requests_mock.register_uri(rm.ANY, rm.ANY, exc=rm.exceptions.InvalidRequest)
    return requests_mock

$ ruff check --select F823 ./F823.py
F823.py:
  6:32 F823 Local variable `requests_mock` referenced before assignment
    |
  4 | @pytest.fixture()
  5 | def requests_mock(requests_mock: rm.Mocker) -> rm.Mocker:
  6 |     requests_mock.register_uri(rm.ANY, rm.ANY, exc=rm.exceptions.InvalidRequest)
    |                                ^^ F823
  7 |     return requests_mock
    |
  
Found 1 error.

Apparently, ruff doesn't handle the renamed import correctly. When renaming the pytest fixture function or the fixture argument, which both can't be done because it's a global fixture override in our test code, then ruff doesn't raise an error.

F823 wasn't an issue in 0.0.272 but it now is after upgrading to 0.0.280. The last modification of that rule was in #6036.

[charliermarsh]

I think this is my bad, I will fix this in time for Monday’s release.

[charliermarsh]

This should be fixed in v0.0.282, which is out now.