Scan-skip test goes blind if the call chain grows 3 frames (#707)

test/core/cache-retention-maintenance.test.js

@@ -1089,7 +1089,27 @@ test('a partition already due for compaction skips the resettle-candidate row sc
  // read, so it attributes each read to its caller instead of only counting
  // reads tick-wide (a second legitimate read elsewhere in the tick, e.g. a
  // footer-stats probe, would not falsely implicate the scan).
+ //
+ // A stack-based observation can go blind: the deciding frame sits ~8 frames
+ // below the mock, and V8's default `Error.stackTraceLimit` of 10 leaves only
+ // two frames of headroom. Three more frames anywhere between the mock and
+ // the caller (an icebird refactor, extra node:test mock internals, a wrapper
+ // in `resolver.js`) would drop it, and a negative "no stack mentions
+ // `hasResettleCandidate`" assertion passes vacuously on truncated stacks.
+ // Two guards keep that from happening silently:
+ // 1. raise `Error.stackTraceLimit` while the mock is installed (restored
+ // below even if the test throws), which removes the hazard outright;
+ // 2. assert positively that some stack names `compactGeneration`, the
+ // legitimate reader. It calls `scanRowsFromTable` from exactly the same
+ // depth as `hasResettleCandidate` does, so any truncation deep enough
+ // to hide the frame the negative assertion hunts for also hides this
+ // one, and the test fails loudly instead of going quiet. Asserting on
+ // `scanRowsFromTable` itself would not do: it sits one frame shallower
+ // and survives truncation that has already blinded the real check.
+ // Guard 2 also catches the `?? ''` fallback below storing an unattributable
+ // empty string.
  const cacheRoot = await makeTmpDir('maint-scan-skip')
+ const originalStackTraceLimit = Error.stackTraceLimit
  try {
  const partDir = path.join(cacheRoot, 'datasets', 'ds1', 'date=2026-08-08')
  const epoch0 = path.join(partDir, 'epoch=0')
@@ -1104,6 +1124,7 @@ test('a partition already due for compaction skips the resettle-candidate row sc
  /** @type {string[]} */
  const stacks = []
  const original = fsSync.readFileSync
+ Error.stackTraceLimit = 50
  t.mock.method(fsSync, 'readFileSync', function (p, ...rest) {
  if (String(p).endsWith('.parquet')) stacks.push(new Error().stack ?? '')
  return original.call(this, p, ...rest)
@@ -1122,12 +1143,17 @@ test('a partition already due for compaction skips the resettle-candidate row sc
  assert.equal(report.totalCompacted, 1, 'sanity: compaction actually ran')
 
  assert.ok(stacks.length > 0, 'sanity: the data file was read at all')
+ assert.ok(
+ stacks.some((s) => s.includes('compactGeneration')),
+ 'sanity: captured stacks must be deep enough to name the reader, or the assertion below passes vacuously'
+ )
  assert.deepEqual(
  stacks.filter((s) => s.includes('hasResettleCandidate')),
  [],
  'the resettle scan must not read the data file'
  )
  } finally {
+ Error.stackTraceLimit = originalStackTraceLimit
  await fs.rm(cacheRoot, { recursive: true, force: true })
  }
 })