Fix unsafe utils.safe_infer

[cdce8p]

Type of Changes

	Type
✓	🐛 Bug fix

Description

Came across an error while testing Home Assistant. safe_infer here assumes that value is a FunctionDef to be able to access value.args.args. The assumption is never fully checked however. value could also be an <Instance of builtins.function ...> which would cause an AttributeError.

I wasn't able to write a dedicated regression test unfortunately. Home Assistant only managed to break it with some combination of patching a builtin function and custom plugins which import parts of the checked files itself.

The condition was originally added in #5409

[coveralls]

Pull Request Test Coverage Report for Build 1802774914

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 93.935%

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Totals
Change from base Build 1802733185:	0.0%
Covered Lines:	14854
Relevant Lines:	15813

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💛 - Coveralls

[Pierre-Sassoulas]

Nice catch ! home-assistant is in the primer though: https://github.com/PyCQA/pylint/blob/main/tests/primer/packages_to_lint_batch_one.json#L26?, was it only on a branch (not yet merged maybe) ?

[cdce8p]

Nice catch ! home-assistant is in the primer though: https://github.com/PyCQA/pylint/blob/main/tests/primer/packages_to_lint_batch_one.json#L26?, was it only on a branch (not yet merged maybe) ?

It was in dev, but only merged a few days ago. The issue was only visible because of a custom plugin and then only if the time module was imported in a certain way. Pretty strange tbh. Might be the reason why it didn't show up in the primer tests. I did check astroid, but that seemed to do what was expected.

In the meantime, a fix for Home Assistant has been merged. So it definitely won't show up in the tests anymore.
home-assistant/core#65911

The fix here is never the less useful. If for nothing else then type safety (and mypy).