Debug-action-cache

The silent failures are the most dangerous. Consider these scenarios:

Standard logs just show Received 0 of 0 artifacts. That is useless. To see the truth, you need step-level debug logging, specifically for the cache action.

GitHub doesn’t let you browse caches directly, but you can list them via API:

gh api \
  -H "Accept: application/vnd.github+json" \
  /repos/:owner/:repo/actions/caches

Look at:

This explains why a key isn’t matching.

Problem: Cache restored only 20% of the time.

Logs show: Cache not found for key: linux-npm-xyz123 debug-action-cache

Check key generation:

- name: Debug cache key
  run: |
    echo "key: $ runner.os -npm-$ hashFiles('**/package-lock.json') "
    ls -la **/package-lock.json

Output shows:
package-lock.json changes every build (e.g., due to npm install --package-lock-only differences).

Fix:

key: $ runner.os -npm-$ hashFiles('package-lock.json') 
restore-keys: |
  $ runner.os -npm-

Now even if exact key misses, it restores the most recent linux-npm-* cache.

True mastery of debug-action-cache is not reactive—it is proactive. Implement these strategies:

- name: Report cache metrics
  run: |
    if [ -d "node_modules" ]; then
      echo "cache_status=hit" >> $GITHUB_OUTPUT
    else
      echo "cache_status=miss" >> $GITHUB_OUTPUT
    fi