fix(scripts): resolve worktree root before relative_to in type_check_gate

[yuneng-berri]

Relevant issues

Linear ticket

Pre-Submission checklist

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• I have added meaningful tests
• My PR passes all CI/CD checks (e.g., lint, format, unit tests)
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Screenshots / Proof of Fix

The failure mechanism, reproduced on macOS:

$ python3 -c "from pathlib import Path; import tempfile; d=Path(tempfile.mkdtemp()); print((d/'x').resolve().relative_to(d))"
ValueError: '/private/var/folders/08/.../T/tmphmqa3g1v/x' is not in the subpath of '/var/folders/08/.../T/tmphmqa3g1v'

Before the fix, every local make lint-basedpyright on a Mac died with "basedpyright produced no errors for the base tree ... refusing to blame this change for it". After the fix, with no TMPDIR workaround:

$ env -u TMPDIR make lint-basedpyright
(uv run --no-sync basedpyright --outputjson || true) | uv run --no-sync python scripts/type_check_gate.py --base origin/litellm_internal_staging
OK: every rule is within its basedpyright limit or no higher than base (154833 errors total)

The new regression test fails on the old code and passes with the fix:

$ git stash -- scripts/type_check_gate.py && uv run pytest tests/test_litellm/test_type_check_gate.py::test_symlinked_root_keeps_diagnostics_in_tree -q
FAILED tests/test_litellm/test_type_check_gate.py::test_symlinked_root_keeps_diagnostics_in_tree
$ git stash pop && uv run pytest tests/test_litellm/test_type_check_gate.py -q
18 passed in 0.13s

Type

🐛 Bug Fix

Changes

On macOS, tempfile.mkdtemp() returns a path under /var/folders/..., which is a symlink to /private/var/.... The base pass of scripts/type_check_gate.py runs basedpyright in a temp worktree there, and _to_relative resolved each diagnostic path (yielding /private/var/...) but not the worktree root, so relative_to raised ValueError for every diagnostic. Every base diagnostic was dropped, base counts came back empty, and the vacuous-run guard failed the run. Since make pre-commit includes this gate for any litellm/ Python change, it always failed locally on a Mac. CI runs Linux where the temp dir is not a symlink, so it never saw this

The fix resolves the root as well: absolute.resolve().relative_to(root.resolve()). The sibling gates are fine; scripts/type_discipline_gate.py already resolves root for exactly this reason and scripts/ruff_strict_gate.py counts rule codes straight from ruff JSON without computing worktree-relative paths

The regression test builds an explicit symlinked root instead of relying on the macOS /var symlink, so it exercises the bug on Linux CI too

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[greptile-apps]

Greptile Summary

Fixes a ValueError in scripts/type_check_gate.py caused by calling relative_to(root) after resolving the diagnostic path — leaving root unresolved while its resolved form differs (e.g., macOS /var → /private/var). The one-line change adds .resolve() to root so both sides of relative_to are canonicalized consistently.

• scripts/type_check_gate.py: _to_relative now calls root.resolve() alongside absolute.resolve(), matching the pattern already used in scripts/type_discipline_gate.py.
• tests/test_litellm/test_type_check_gate.py: Adds test_symlinked_root_keeps_diagnostics_in_tree which constructs an explicit symlink via tmp_path, reproducing the failure on Linux CI without requiring the macOS-specific /var symlink.

Confidence Score: 5/5

The change is isolated to a developer tooling script and its test; no production code is touched.

The fix is a single .resolve() call that aligns the gate's behavior with the sibling type_discipline_gate.py script. The new regression test explicitly reproduces the failure on all platforms, all 18 existing tests continue to pass, and the scope is limited to the CI linting pipeline.

No files require special attention.

Important Files Changed

Filename	Overview
scripts/type_check_gate.py	Single-character fix in _to_relative: adds .resolve() on root so both sides of relative_to are symlink-resolved, matching the already-resolved diagnostic path. Correct and minimal.
tests/test_litellm/test_type_check_gate.py	Adds test_symlinked_root_keeps_diagnostics_in_tree which builds an explicit symlinked root via tmp_path, exercising the bug on Linux CI without requiring the macOS /var symlink. All existing tests are untouched.

_{Reviews (1): Last reviewed commit: "Merge remote-tracking branch 'origin/lit..." | Re-trigger Greptile}