name: Cache npm package downloads
description: Restore npm's download cache. Trusted default-branch jobs that opt in may save it.
inputs:
  save:
    description: Save the shared download cache when this event is allowed to write it.
    required: false
    default: "false"
outputs:
  can-save:
    description: Whether this run may update the shared npm download cache.
    value: ${{ steps.context.outputs.can-save }}
  path:
    description: The npm download-cache directory.
    value: ${{ steps.context.outputs.path }}
runs:
  using: composite
  steps:
    - id: context
      shell: bash
      env:
        DEFAULT_BRANCH: ${{ github.event.repository.default_branch }}
        LOCKFILES_HASH: ${{ hashFiles('package-lock.json', 'npm-shrinkwrap.json', '.npmrc') }}
      run: |
        cache_path="$(npm config get cache)"
        runtime_arch="$(node -p 'process.arch')"
        can_save=false
        if [[ -n "${DEFAULT_BRANCH}" && "${GITHUB_REF}" == "refs/heads/${DEFAULT_BRANCH}" && ( "${GITHUB_EVENT_NAME}" == "push" || "${GITHUB_EVENT_NAME}" == "schedule" || "${GITHUB_EVENT_NAME}" == "workflow_dispatch" ) ]]; then
          can_save=true
        fi
        cache_key="npm-download-${RUNNER_OS}-${runtime_arch}-${LOCKFILES_HASH}"
        # Same platform only. A lockfile change can reuse tarballs from the previous key.
        restore_key="npm-download-${RUNNER_OS}-${runtime_arch}-"
        {
          printf 'can-save=%s\n' "${can_save}"
          printf 'path=%s\n' "${cache_path}"
          printf 'key=%s\n' "${cache_key}"
          printf 'restore-key=%s\n' "${restore_key}"
        } >> "${GITHUB_OUTPUT}"
    - name: Restore and save npm package downloads
      if: steps.context.outputs.can-save == 'true' && inputs.save == 'true'
      uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
      with:
        path: ${{ steps.context.outputs.path }}
        key: ${{ steps.context.outputs.key }}
        restore-keys: ${{ steps.context.outputs.restore-key }}
    - name: Restore npm package downloads without saving
      if: steps.context.outputs.can-save != 'true' || inputs.save != 'true'
      uses: actions/cache/restore@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
      with:
        path: ${{ steps.context.outputs.path }}
        key: ${{ steps.context.outputs.key }}
        restore-keys: ${{ steps.context.outputs.restore-key }}