BUILD-11297 Simplify CI_METRICS_ENABLED gate — strict 'true', no bash step

[julien-carsique-sonarsource]

Summary

Fix a regression introduced by #62 (BUILD-11294 — cache metrics): the metrics-flag shell step crashed on macOS runners with bad substitution because ${VAR,,} lowercase substitution is bash 4+ only (Apple ships bash 3.2). The crash cascaded into a template-validity error for downstream build-maven if: expressions in consumer workflows.

Observed in: sonar-dummy#592 Build macOS, run 26091741374, step 5 line 884.

Fix

Drop the bash step entirely; check env.CI_METRICS_ENABLED == 'true' directly in the cache-metrics-prep step's if: expression.

• No more bash — zero portability surface across runner platforms.
• Strict literal 'true' — matches the convention of the existing env vars in this action (CACHE_BACKEND, CACHE_IMPORT_GITHUB). The earlier case-insensitive logic (${VAR,,} == 'true' accepting True / TRUE / true) was an artifact of bash 4 only; GHA expressions don't have tolower, so encoding the same semantic in YAML would require listing variants explicitly. Strict 'true' is simpler and consistent.
• Linux-only scope preserved — the combined if: runner.os == 'Linux' && env.CI_METRICS_ENABLED == 'true' keeps the metrics flow Linux-only. The downstream cache-metrics step continues to chain on steps.cache-metrics-prep.outputs.prepared == 'true', so when the flag is unset or non-'true' the entire pipeline is skipped without warning.

Why ship this now (separate from M2 macOS compliance)

The metrics-flag bash step ran unconditionally on every consumer call to gh-action_cache@master. On macOS, bash 3.2 errored on ${RAW,,} regardless of whether CI_METRICS_ENABLED was set — i.e. this broke the base cache flow on macOS for everyone, not just metrics-pilot repos. Restoring base-flow correctness is independent of (and prerequisite to) the M2 work that will add macOS metrics emission.

Behavior on non-Linux after this fix

• CI_METRICS_ENABLED=true set, macOS/Windows runner: cache flow runs unchanged (as it did before BUILD-11294 Add cache-size-bytes output and pipeline runtime metrics JSON #62). No metrics emission, no JSON written, no crash. Matches the documented "Linux only" promise in the README.
• macOS metrics emission remains scoped to M2 (BUILD-11298–11300, WarpBuild AMI work).

Test plan

• Vitest suite green (48 cases)
• All lines in action.yml, cache-metrics/action.yml ≤ 140 cols
• Markdownlint clean on README
• CI on this branch
• Consumer dogfood: sonar-dummy macOS job no longer crashes

Related

• Parent epic: BUILD-11068
• Pilot rollout ticket: BUILD-11297 (M1.9, surfaced this bug on sonar-dummy macOS)
• Original PR: #62 (BUILD-11294)
• Consumer dogfood: SonarSource/sonar-dummy#592
• Future macOS metrics emission: BUILD-11298 – BUILD-11300 (M2, WarpBuild AMI)

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues
0 New dependency risks

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonarqube-cloud-us]

Quality Gate passed

Issues
0 New issues
0 Accepted issues
0 New dependency risks

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[sonar-review-alpha]

Summary

Problem: The bash 4+ feature ${VAR,,} (lowercase) in the "Resolve CI_METRICS_ENABLED flag" step crashes on macOS runners (bash 3.2), breaking the entire cache flow with a "bad substitution" error.

Solution: Eliminate the bash step entirely. Evaluate CI_METRICS_ENABLED directly in the downstream if: expression with a strict literal 'true' check. This removes the macOS portability issue while preserving the Linux-only metrics gate (runner.os == 'Linux').

Scope of changes:

• action.yml: Removed 12-line bash step, changed if: condition from steps.metrics-flag.outputs.enabled == 'true' to env.CI_METRICS_ENABLED == 'true'
• README.md: Updated CI_METRICS_ENABLED docs to specify strict 'true' literal (removed "case-insensitive" language)
• cache-metrics/action.yml: Comment formatting only
• All changes kept to ≤140 character line length per existing project convention

What reviewers should know

Key review points:

1. The condition change is the crux — verify the if: runner.os == 'Linux' && env.CI_METRICS_ENABLED == 'true' logic matches the intended behavior. The step now runs when both: (a) runner is Linux, and (b) the env var is the literal string 'true'. Unset or any other value skips it silently (fail-open).

2. Documentation change is semantic, not just cosmetic — the README now documents strict 'true' matching instead of case-insensitive. This is consistent with the behavior change and matches how other env vars in this action (CACHE_BACKEND, CACHE_IMPORT_GITHUB) work.

3. Behavior preservation — non-Linux runners with CI_METRICS_ENABLED=true still skip metrics (no change from before #62). The next step's chaining on steps.cache-metrics-prep.outputs.prepared == 'true' ensures graceful skip when the condition is false or when the step itself fails.

4. No functional change on Linux — Linux runners with the flag set to 'true' behave identically; only the path to evaluate the condition is different (expression vs. bash).

Testing impact: Vitest suite passes; CI/consumer dogfood (sonar-dummy macOS job) is the real validation.

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[sonar-review-alpha]

LGTM! ✅

Straightforward and correct fix. The removed metrics-flag step has no remaining references anywhere in the repo. The downstream "Emit cache metrics" step still chains on steps.cache-metrics-prep.outputs.prepared == 'true' (unchanged), keeping the fail-open behaviour intact. The env.CI_METRICS_ENABLED expression context is the same GHA env context that the old bash step already used (env: RAW: ${{ env.CI_METRICS_ENABLED }}), so variable resolution is equivalent — only the case-insensitivity is lost, which is intentional and fully documented. All "case-insensitive" language is consistently removed from the README with no stale mentions remaining.

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