[NO-SQUASH-MERGE] fix varnames on py3.14 deferred annotations

[RonnyPfannschmidt]

closes #629

using direct attributes instead of signature to avoid the extra objects

[Copilot]

Pull request overview

Fixes pluggy._hooks.varnames() to avoid inspect.signature() on Python 3.14+ (where deferred/string annotations may be resolved and can fail), and adds coverage + benchmarks around the new behavior.

Changes:

• Reimplements varnames() using __code__, __defaults__, and __qualname__ instead of inspect.signature().
• Adds a regression test for annotations that cannot be resolved at runtime.
• Extends benchmark suite to compare the new implementation against a legacy inspect.signature() version.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/pluggy/_hooks.py	Updates varnames() implementation to avoid annotation resolution and reduce overhead.
testing/test_helpers.py	Adds a regression test ensuring varnames() works with unresolvable string annotations.
testing/benchmark.py	Adds microbenchmarks comparing new vs legacy varnames() approaches.

Comments suppressed due to low confidence (1)

src/pluggy/_hooks.py:298

• Typo in the varnames docstring: "keywrord" should be "keyword".

def varnames(func: object) -> tuple[tuple[str, ...], tuple[str, ...]]:
    """Return tuple of positional and keywrord argument names for a function,
    method, class or callable.

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[bluetech]

I'm a bit wary of stopping to use inspect.signature. It means we drop support for stuff like __signature__ and __text_signature__ and whatever weird stuff inspect.signature supports.

The performance is definitely nice but if I'm not mistaken varnames is only used #hookspecs + #hookimpls times so not very performance critical.

Nonetheless, if you think it should be fine, I would at least suggest running some downstream tests (see downstream/ directory) to make sure there are no regressions (I usually run it before release).

[RonnyPfannschmidt]

fixing the downstream tests now (scripts are bitrot affected)