Python: Allow trailing commas in type parameter lists

[jketema]

Vibe coded by Copilot.

Trailing commas in PEP 695 type parameter lists are valid Python syntax and are emitted by formatters when a list is split across lines. Accept an optional trailing comma in the Tree-sitter grammar and add extractor parser coverage for type aliases, functions, and classes.

Fixes #22739

Testing

• pytest -q tests/test_parser.py (39 passed)

[Copilot]

Copilot review overview

🟡 Changes recommended

The compiled parser source must be regenerated and committed for clean builds to include the fix.

Review effort: Balanced
Findings: 1

Open (1)

• Regenerate and commit parser artifacts for Rust builds · New

What changed in this PR

Updates the Python extractor grammar to accept trailing commas in PEP 695 type parameter lists, addressing #22739.

Changes:

• Allows an optional trailing comma in the grammar.
• Adds parser fixtures for type aliases, functions, and classes.

File	Description
python/​extractor/​tsg-python/​tsp/​src/​grammar.json	Updates the generated grammar definition.
python/​extractor/​tsg-python/​tsp/​grammar.js	Allows trailing commas in type parameter lists.
python/​extractor/​tests/​parser/​type_parameters_new.py	Adds regression inputs for all three declaration forms.
python/​extractor/​tests/​parser/​type_parameters_new.expected	Records expected parser output.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[tausbn]

Looks good to me. Needs to be rebased and regenerated, since other changes to the extractor were merged.

(Also, usually an extractor change should come with a version bump in util.py, but in this case it was bumped last week, so I don't think we need to do so again.)

[jketema]

(Also, usually an extractor change should come with a version bump in util.py, but in this case it was bumped last week, so I don't think we need to do so again.)

Was that before after the release was branched? If it was before we might still want to bump.

[tausbn]

I think it was after, but to be sure, you can just bump it again.

[jketema]

Looks good to me. Needs to be rebased and regenerated, since other changes to the extractor were merged.

Copilot did its thing.