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rule for ValueError: I/O operation on closed file. #10517

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tooptoop4 opened this issue Mar 22, 2024 · 5 comments · May be fixed by #15865
Open

rule for ValueError: I/O operation on closed file. #10517

tooptoop4 opened this issue Mar 22, 2024 · 5 comments · May be fixed by #15865
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rule Implementing or modifying a lint rule

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@tooptoop4
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ruff does not complain about:

with open('/a.txt', "w") as f:
    f.write('a')
with open('/b.txt', "w"):
    f.write('b')

but python does:

ValueError: I/O operation on closed file.
@MichaReiser MichaReiser added the rule Implementing or modifying a lint rule label Mar 22, 2024
@MichaReiser
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MichaReiser commented Mar 22, 2024 •
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Do you think the rule could be generalized to disallow method calls on any object defined in a context expression after the with statement?

@zanieb
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zanieb commented Mar 22, 2024

@MichaReiser no, you can safely use many objects after their context is exited :) we'd need type-inference for that to be broadly correct.

@autinerd
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For example with with pytest.raises() as exc_info you have to use the object after the context is exited.

@charliermarsh
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We would probably need to make this specific to open calls (which would be okay).

@tooptoop4
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https://github.com/wemake-services/wemake-python-styleguide?tab=readme-ov-file finds this

flake8 --select WPS441 somefile.py

https://wemake-python-styleguide.readthedocs.io/en/0.16.1/pages/usage/violations/best_practices.html#wemake_python_styleguide.violations.best_practices.ControlVarUsedAfterBlockViolation

@InSyncWithFoo InSyncWithFoo linked a pull request Feb 1, 2025 that will close this issue
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[ruff] IO operations performed on closed IO objects (RUF050) InSyncWithFoo/ruff
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@MichaReiser @charliermarsh @zanieb @autinerd @tooptoop4