benchmark.yml

name: 'Benchmarks'

# Perf numbers are noisy on shared runners, so benchmarks never gate PRs. They run on each
# published release (and on demand) to refresh the Benchmarks section of the README.
on:
  release:
    types: [published]
  workflow_dispatch:
    inputs:
      version:
        description: 'Version label to record (defaults to package.json version)'
        required: false
        type: string
      open_pr:
        description: 'Open a PR with the refreshed README'
        required: false
        default: true
        type: boolean

permissions:
  contents: write
  pull-requests: write

jobs:
  benchmark:
    name: 'Run benchmarks (Node 20)'
    runs-on: ubuntu-latest
    steps:
      - name: Checkout default branch
        uses: actions/checkout@v4
        with:
          ref: ${{ github.event.repository.default_branch }}

      - name: Set up Node
        uses: actions/setup-node@v4
        with:
          node-version: '20'
          cache: 'npm'

      - name: Resolve version label
        id: ver
        run: |
          RAW="${{ github.event.release.tag_name || inputs.version }}"
          echo "value=${RAW#v}" >> "$GITHUB_OUTPUT"

      # The benchmark adapter loads lambda-api from the working tree via require('../../'),
      # which resolves through the root package's "main" (./dist/cjs/index.js). That path
      # only exists after a build, so the root package must be installed and built first.
      - name: Install root dependencies
        run: npm ci --ignore-scripts

      - name: Build dist (CJS + ESM)
        run: npm run build

      - name: Install benchmark dependencies
        working-directory: benchmarks
        run: npm ci

      - name: Run benchmarks and refresh README
        working-directory: benchmarks
        env:
          LAMBDA_API_VERSION: ${{ steps.ver.outputs.value }}
        run: node run.js --md results/RESULTS.md --json results/raw.json --update-readme

      # Keep the committed README Prettier-clean so the PR doesn't fail main's CI.
      - name: Format README
        run: npx --yes prettier@2 --write README.md

      - name: Upload raw results
        uses: actions/upload-artifact@v4
        with:
          name: benchmark-results
          path: benchmarks/results/

      - name: Add results to job summary
        run: cat benchmarks/results/RESULTS.md >> "$GITHUB_STEP_SUMMARY"

      # The default branch doesn't accept direct pushes, so the refreshed README goes
      # through a PR. Each run gets its own branch so concurrent or repeated runs never
      # clobber one another.
      - name: Open PR with refreshed README
        if: ${{ github.event_name == 'release' || inputs.open_pr }}
        env:
          GH_TOKEN: ${{ github.token }}
          BASE: ${{ github.event.repository.default_branch }}
          VERSION: ${{ steps.ver.outputs.value }}
        run: |
          if git diff --quiet -- README.md; then
            echo 'README.md unchanged — no PR needed'
            exit 0
          fi

          LABEL="${VERSION:-manual}"
          BRANCH="benchmarks/refresh-${LABEL}-${GITHUB_RUN_ID}"

          git config user.name 'github-actions[bot]'
          git config user.email 'github-actions[bot]@users.noreply.github.com'
          git switch -c "$BRANCH"
          git add README.md
          git commit -m "docs: update benchmark results for ${LABEL}"
          git push origin "$BRANCH"

          {
            echo "Automated refresh of the Benchmarks section of the README, generated by [this run](${GITHUB_SERVER_URL}/${GITHUB_REPOSITORY}/actions/runs/${GITHUB_RUN_ID})."
            echo
            echo "Version label: \`${LABEL}\` · Trigger: \`${GITHUB_EVENT_NAME}\`"
            echo
            echo "Perf numbers come from a shared GitHub-hosted runner and are noisy between runs, so treat"
            echo "movement within a few percent as noise rather than a regression."
            echo
            echo '<details><summary>Full results</summary>'
            echo
            cat benchmarks/results/RESULTS.md
            echo
            echo '</details>'
          } > /tmp/pr-body.md

          gh pr create \
            --base "$BASE" \
            --head "$BRANCH" \
            --title "docs: refresh benchmark results for ${LABEL}" \
            --body-file /tmp/pr-body.md