fix(scripts): make the R7a bash-3.2 control hold on a host that IS bash 3.2

scripts/objectui-changeset-digest.mjs

@@ -2770,22 +2770,90 @@ function selfTest() {
  // script under test inherits it through `spawnSync`.
  const noBash4 = join(tmp, 'no-bash4-builtins.sh');
  writeFileSync(noBash4, 'enable -n mapfile readarray 2>/dev/null\n');
+
  // The instrument must not be vacuous. If BASH_ENV were ever ignored (a
  // posix-mode bash, a future harness change), R7b would pass by proving
  // nothing, so the disabling is measured on a probe FIRST, both ways.
+ //
+ // ⭐ #12254 — that probe used to be `mapfile` ITSELF, which made this leg a
+ // GUARANTEED FAIL on the one platform it exists to model. On stock macOS
+ // `/bin/bash` IS 3.2, so `mapfile` is missing from the plain run too: the
+ // leg reported `plain=` empty exactly like `sim.out=`, "the simulation
+ // removed something" could not be satisfied by any correct harness, and
+ // `check:objectui-changeset` sat red on every macOS seat while CI
+ // (ubuntu-latest, bash 5) stayed green — so nothing would ever catch it.
+ // A control written to stop a vacuous pass had become a platform-
+ // conditional failure, which is the SAME error family one level up: a
+ // check whose own precondition was never measured across the population of
+ // hosts it runs on.
+ //
+ // The fix is to stop hardcoding a belief about another platform's builtin
+ // table and ASK THE HOST. `probeBuiltin` is chosen at runtime from bash
+ // 2.x-era builtins that (a) this shell reports as a builtin and (b) have no
+ // external `/usr/bin` twin to fall through to — so `enable -n` on one
+ // produces the very same 127 "command not found" that a missing bash-4
+ // builtin produces on 3.2, and the leg measures the HARNESS instead of the
+ // platform. Deliberately not a skip: a host that offers no qualifying
+ // builtin fails this leg loudly, because a control that quietly does
+ // nothing is the exact shape R7a exists to prevent.
+ const probeCandidates = ['shopt', 'caller', 'compgen', 'hash', 'umask'];
+ const pickProbe = spawnSync(
+ 'bash',
+ [
+ '-c',
+ 'for b in "$@"; do ' +
+ '[ "$(type -t "$b" 2>/dev/null)" = builtin ] || continue; ' +
+ '[ -n "$(type -P "$b" 2>/dev/null)" ] && continue; ' +
+ 'printf %s "$b"; exit 0; done; exit 1',
+ 'pick-probe-builtin',
+ ...probeCandidates,
+ ],
+ { encoding: 'utf8' },
+ );
+ const probeBuiltin = pickProbe.stdout.trim();
+ const builtinProbe = join(tmp, 'builtin-probe.sh');
+ writeFileSync(builtinProbe, `${probeBuiltin} >/dev/null\nprintf 'PROBE-STATUS=%s\\n' "$?"\n`);
+ const noProbeBuiltin = join(tmp, 'no-probe-builtin.sh');
+ writeFileSync(noProbeBuiltin, `enable -n ${probeBuiltin} 2>/dev/null\n`);
+ const probePlain = spawnSync('bash', [builtinProbe], { encoding: 'utf8' });
+ const probeSim = spawnSync('bash', [builtinProbe], {
+ encoding: 'utf8',
+ env: { ...process.env, BASH_ENV: noProbeBuiltin },
+ });
+ const probeStatus = (r) => (r.stdout.match(/PROBE-STATUS=(\d+)/) ?? [])[1];
+ check(
+ '#12071/#12254 R7a the BASH_ENV harness really removes a builtin THIS host has (else R7b proves nothing)',
+ probeBuiltin !== '' &&
+ probeStatus(probePlain) !== undefined &&
+ probeStatus(probePlain) !== '127' &&
+ probeStatus(probeSim) === '127' &&
+ probeSim.stderr.includes(probeBuiltin),
+ `builtin=${probeBuiltin || `<none of ${probeCandidates.join(',')} qualified on this host>`} ` +
+ `plain=${probePlain.stdout.trim()} sim=${probeSim.stdout.trim()} sim.err=${probeSim.stderr.trim()}`,
+ );
+
+ // …and separately, the state R7b actually depends on: in the shell R7b
+ // runs, `mapfile` is unavailable. This holds on BOTH hosts and for
+ // DIFFERENT reasons — `enable -n` removed it on bash 5, it was never there
+ // on bash 3.2 — which is why it is its own leg rather than folded into the
+ // harness leg above: neither leg alone is unconditional, and together they
+ // leave no host on which R7b can pass vacuously. The detail line names
+ // which way this host got there, so a macOS operator reading a GREEN run
+ // still learns that their `/bin/bash` is the genuine 3.2 article.
  const mapfileProbe = join(tmp, 'mapfile-probe.sh');
  writeFileSync(mapfileProbe, 'mapfile -t x < <(printf "a\\n") && echo MAPFILE-WORKS\n');
- const probePlain = spawnSync('bash', [mapfileProbe], { encoding: 'utf8' });
- const probeSim = spawnSync('bash', [mapfileProbe], {
+ const mapfilePlain = spawnSync('bash', [mapfileProbe], { encoding: 'utf8' });
+ const mapfileSim = spawnSync('bash', [mapfileProbe], {
  encoding: 'utf8',
  env: { ...process.env, BASH_ENV: noBash4 },
  });
+ const hostHasMapfile = mapfilePlain.stdout.includes('MAPFILE-WORKS');
  check(
- '#12071 R7a the simulated-3.2 harness really removes the builtin (else R7b proves nothing)',
-probePlain.stdout.includes('MAPFILE-WORKS') &&
- !probeSim.stdout.includes('MAPFILE-WORKS') &&
-probeSim.stderr.includes('mapfile'),
-`plain=${probePlain.stdout.trim()} sim.out=${probeSim.stdout.trim()} sim.err=${probeSim.stderr.trim()}`,
+ '#12071/#12254 R7a2 … and in the R7b shell mapfile is gone, however this host got there',
+!mapfileSim.stdout.includes('MAPFILE-WORKS') && mapfileSim.stderr.includes('mapfile'),
+`host-has-mapfile=${hostHasMapfile} (${
+hostHasMapfile ? 'bash 4+, so enable -n has to remove it' : 'host bash is already 3.2-era, nothing to remove'
+}) sim.out=${mapfileSim.stdout.trim()} sim.err=${mapfileSim.stderr.trim()}`,
  );
 
  // The R2 shape again — pushed, never merged — through a shell that has no