impl LSP: Navigation support for pytest fixtures #1901

[asukaminato0721]

Summary

Fixes #1901

Implemented pytest import/alias detection plus fixture discovery and parameter scanning in pyrefly/lib/state/lsp.rs, and hooked it into go‑to‑definition and local references.

todo: should these pytest functions in their own mod?

Test Plan

cargo test pytest_fixture_parameter_goes_to_fixture_definition

cargo test pytest_fixture_references_include_injected_parameters

[Copilot]

Pull request overview

This PR implements LSP navigation support for pytest fixtures, enabling go-to-definition and find-references functionality for fixture parameters in test functions. When a developer invokes go-to-definition on a fixture parameter (e.g., my_fixture in def test_thing(my_fixture):), the LSP will navigate to the fixture definition. Similarly, finding references on a fixture definition will include all test/fixture functions that use it as a parameter.

Changes:

• Added pytest import and fixture detection logic to identify pytest modules and fixture decorators
• Implemented fixture discovery and parameter scanning to collect fixture definitions and their usage in test functions
• Integrated pytest fixture resolution into LSP go-to-definition and find-references operations

Reviewed changes

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

File	Description
pyrefly/lib/state/lsp.rs	Core implementation: added PytestAliases tracking, fixture detection functions, and integrated pytest-aware parameter resolution into LSP operations
pyrefly/lib/test/lsp/definition.rs	Added test verifying go-to-definition navigation from fixture parameters to fixture definitions
pyrefly/lib/test/lsp/local_find_refs.rs	Added test verifying find-references includes injected fixture parameters in test functions

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[kinto0]

todo: should these pytest functions in their own mod?

for sure. maybe a pyrefly/lib/third_party or something similar?

[meta-codesync]

@migeed-z has imported this pull request. If you are a Meta employee, you can view this in D91537491.

[asukaminato0721]

https://stackoverflow.com/questions/77318902/why-using-yield-instead-of-return-in-pytest-fixtures aa, not only return but yield

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[kinto0]

a few small nits. I can clean them up on import

[yangdanny97]

Review automatically exported from Phabricator review in Meta.

[kinto0]

from @yangdanny97 :
do we want tests to check what happens if the parameter name doesn't exist as a function somewhere, or if the function exists but isn't a fixture, or if the function we're trying GTD isn't a top-level test function?

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅

[yangdanny97]

Review automatically exported from Phabricator review in Meta.

[meta-codesync]

@kinto0 merged this pull request in 711d99f.