ESM config compatibility for vitest

[Saga4]

No description provided.

[codeflash-ai]

⚡️ Codeflash found optimizations for this PR

📄 11% (0.11x) speedup for fix_import_path_for_test_location in codeflash/languages/javascript/instrument.py

⏱️ Runtime : 4.49 milliseconds → 4.03 milliseconds (best of 174 runs)

A new Optimization Review has been created.

🔗 Review here

[claude]

PR Review Summary

Prek Checks

✅ All checks pass — ruff check and ruff format both clean.

Mypy

⚠️ 198 mypy errors found in changed files, but all are pre-existing on main (same files have the same errors on the base branch). No new type errors introduced by this PR.

Code Review

Key changes in this PR:

1. .js → .mjs config rename (vitest_runner.py): Renames codeflash.vitest.config.js to codeflash.vitest.config.mjs — correct fix since the config uses ESM import syntax, which requires .mjs when the project doesn't have "type": "module" in package.json.
2. fix_import_path_for_test_location (instrument.py): New function to rewrite AI-generated import paths to be relative to the test file location.
3. Vitest perf state reset (capture.js): Resets perf state in beforeEach for Vitest (no external loop runner), correctly checking CODEFLASH_PERF_CURRENT_BATCH to distinguish from Jest.
4. Extensive debug logging across parse.py, vitest_runner.py, function_optimizer.py, test_runner.py, support.py.

Outstanding issue (from previous review):

• instrument.py:994-995: The endswith(source_name) match in should_fix_path() is still broad — common names like utils.ts or index.ts could match unrelated imports. Consider adding path segment matching.

No new critical issues found.

Test Coverage

File	Main	PR	Diff
instrument.py	78%	69%	⚠️ -9%
parse.py	51%	49%	-2%
support.py	74%	74%	0%
vitest_runner.py	69%	67%	-2%
function_optimizer.py	18%	18%	0%
test_runner.py	62%	62%	0%
verifier.py	44%	43%	-1%
Overall	79.47%	79.34%	-0.13%

Notes:

• ⚠️ instrument.py dropped 9% due to the new fix_import_path_for_test_location function (~60 lines) having no test coverage. Consider adding unit tests for this function.
• Most other changes are debug logging (logger.debug) which are not exercised in unit tests — acceptable for logging-only changes.
• Overall coverage decrease is minimal (-0.13%).

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Last updated: 2026-02-09T15:15Z

[claude]

Low risk, but worth noting: The endswith(source_name) match on the stem alone is quite broad. If the source file is named something common like utils.ts or index.ts, this could match unrelated imports (e.g., some/other/utils would also get rewritten to the relative path of this source file).

Consider either:

• Adding a check that the import path shares more path segments with the source, or
• Requiring a stricter match (e.g., matching the last 2 path segments)