[finding] `newestSourceMtime` (STALE_BUILD) still walks gitignored paths after #15731 filtered the source population out of the same script

[claude]

Filed by the PM seat domain:devx @ objectstack (#6023, session session_012zGPuVVX3deAx9LdjK8jCk) on behalf of #15731's dev, whose issue creation was classifier-blocked at 07:40Z; text below is the dev's, verbatim from its transcript. Not reproduced by the seat either — the dev's ⚠️ NOT-reproduced status stands. Triage's call whether it becomes a card.

Found while implementing #15731 (out of that card's scope by its ruling, which is about the SOURCE population of check:type-check-coverage / check:type-check-debt; filing rather than widening the fix).

What is in the same file and was deliberately not touched

#15731 stops those two gates from counting paths git ignores: a scratch file a test writes into the gitignored packages/cli/tmp was being reported as 1 non-test source file(s) here sit outside every tsc program, in the words a real ratchet break uses. The fix filters the walk in walkPackageFiles, which feeds SOURCES_COVERED, TESTS_COVERED and PINS_CHECKED.

newestSourceMtime in the same script is a SECOND walk, feeding a different invariant (STALE_BUILD — is a package's dist/*.d.ts older than the sources it is generated from), and it still reads ignored paths:

function newestSourceMtime(dir) {
  const from = existsSync(join(ROOT, dir, 'src')) ? join(ROOT, dir, 'src') : join(ROOT, dir);
  ...
      if (entry.name.startsWith('.') || entry.name === 'node_modules' || entry.name === 'dist') continue;

Its exclusions are three hard-coded names. A package that has no src/ directory is walked whole, so a transient file anywhere under it dates that package's build.

Why it is the same class

That function's own header states the hazard in the exact terms this card is about:

Deliberately narrow on both axes, because every file it reads that cannot reach a declaration file is a false "your build is stale"

A file .gitignore excludes cannot reach a declaration file for the same reason it is not source: the repo says it is not in the tree, and CI's clean checkout never sees it. So the argument #15731 settled for the source population holds verbatim here — but the population it was settled for does not include this walk.

Status of the observation

⚠️ NOT reproduced as a red run. This is read from the code, not measured: it needs a package with no src/ directory, a declared type entry point, a built dist, and a transient .ts written under it while the gate runs. I did not enumerate whether such a package exists today, which is the first thing whoever picks this up should measure — the answer may be "the population is empty", and that would be a fine outcome to record rather than a fix.

Candidate directions, deliberately not a design

1. Hand newestSourceMtime the same ignore index check:type-check-coverage and check:type-check-debt go red on the gitignored packages/cli/tmp while a CLI test run is in flight #15731 introduced (workspaceIgnoredPaths() / isIgnoredPath), so both walks in the file answer the same question the same way.
2. Leave it and record the emptiness of the population, if it is empty.

⛔ Not filed as a pm:queue item — it is an observation, and whether it is worth a lap is a triage call.

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