• ruff v0.0.269
• CPython 3.10.9

Issue

ruff flags a false positive F401 for imports that are used in __all__ that is guarded by a conditional statement.
Running ruff with --fix on will result in broken imports.

MRE

import random


def some_dependency_check():
    return random.uniform(0.0, 1.0) > 0.49999

if some_dependency_check():
    import math

    __all__ = ["math"]
else:
    __all__ = []

-> ruff mre.py
mre.py:9:12: F401 [*] `math` imported but unused
Found 1 error.
[*] 1 potentially fixable with the --fix option.