B008: resolve imported immutable calls

[1678092075]

Fixes #252.

Summary

• resolve direct absolute module-level imports and aliases before matching B008's extend-immutable-calls
• preserve existing source-path matches while invalidating imported bindings after a module-level redefinition
• add focused eval coverage for imports, aliases, negative matches, and shadowing, plus an unreleased changelog entry

Validation

• tox -e py313 — 81 passed, 1 skipped; 97% coverage
• pre-commit run --all-files — isort, Black, flake8, and rstcheck passed
• git diff --check

Scope

This intentionally resolves only direct absolute module-level imports. Nested/local, relative, and star-import resolution remain out of scope, and B039 behavior is unchanged.

[Copilot]

🟡 Changes recommended

Module-scope tracking mishandles annotation-only assignments and misses some walrus rebindings.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds import-aware resolution for B008 immutable-call matching and shadowing detection.

Changes:

• Resolves absolute module imports and aliases.
• Tracks module-level rebinding.
• Adds evaluation tests and changelog entry.

File summaries

File	Description
bugbear.py	Implements import resolution and shadow tracking.
tests/eval_files/b008_extended.py	Tests imports, aliases, and rebinding.
tests/eval_files/b008_extended_shadowing.py	Tests unqualified configuration shadowing.
README.rst	Adds the unreleased changelog entry.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 2
• Review effort level: Balanced

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[cooperlees]

Thanks for this. This seems mostly there, but maybe we can add a test case + handle the walrus operator too? (if I'm understanding correctly copilots finding)

[Copilot]

🟡 Changes recommended

Import resolution misses class methods and several valid module-scope rebinding forms.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review details

Suppressed comments (2)

bugbear.py:804

• This recognizes a walrus only when it is inside exactly one comprehension context. In a nested module-level comprehension, the assignment-expression target still binds at module scope, but contexts contains the module plus both comprehensions, so the imported name remains trusted and later calls are incorrectly exempted. Check that the first context is the module and every remaining context is a comprehension instead of requiring len == 2.

            or (
                len(self.contexts) == 2
                and isinstance(self.contexts[0].node, ast.Module)
                and isinstance(self.contexts[1].node, COMPREHENSION_NODES)
            )

bugbear.py:2504

• Skipping the entire lambda also skips its default expressions, even though those expressions execute immediately when the lambda is created. For a decorator such as @decorate(lambda value=(Depends := Other): value), the module binding is changed before the decorated function's defaults are evaluated, but the stale import mapping still exempts Depends(). Visit the lambda defaults while continuing to skip its deferred body.

class B008NamedExprFinder(NamedExprFinder):
    def visit_Lambda(self, node: ast.Lambda) -> None:  # noqa: B906
        pass

• Files reviewed: 4/4 changed files
• Comments generated: 2
• Review effort level: Balanced