benchmarks.yml

name: benchmarks

on:
  push:
    branches: [main]
  pull_request: {}

permissions:
  contents: read
  pull-requests: write

concurrency:
  group: benchmarks-${{ github.head_ref || github.run_id }}
  cancel-in-progress: true

jobs:
  bench:
    runs-on: ubuntu-latest
    timeout-minutes: 20
    steps:
      - uses: actions/checkout@v6
      - uses: extractions/setup-just@v4
      - uses: astral-sh/setup-uv@v8.2.0
      # uv.lock is git-ignored (repo convention), so a clean checkout lacks it.
      # `just bench-report` builds the compose `application` image, whose Dockerfile
      # does `COPY uv.lock` + `uv sync --frozen`; regenerate the lock first.
      - run: uv lock
      - name: Run the gate and capture the markdown report
        shell: bash
        run: |
          # `docker compose run` leaks buildkit image-build output onto stdout in
          # CI, so a naive capture mixes it into the comment. The report always
          # begins with the `## Benchmark gate` sentinel and the container prints
          # it last, so slice from that heading to EOF -- independent of how
          # compose routes its own noise. Own the exit code manually: `set +e`
          # (shell: bash runs with -e) so a failing gate still lets us post the
          # report, then re-exit with the gate's status so the build still fails.
          set +e
          just bench-report > "$RUNNER_TEMP/raw.log"
          status=$?
          sed -n '/^## Benchmark gate/,$p' "$RUNNER_TEMP/raw.log" \
            | tee "$GITHUB_STEP_SUMMARY" "$RUNNER_TEMP/bench-report.md"
          exit "$status"
      - name: Comment the report on the PR
        # always(): comment even when the gate failed -- that is when it matters most.
        # continue-on-error: fork PRs get a read-only token and cannot comment; the
        # gate above already decided the build, and the run Summary still has the table.
        if: always() && github.event_name == 'pull_request'
        continue-on-error: true
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
        run: |
          gh pr comment "${{ github.event.pull_request.number }}" \
            --edit-last --create-if-none \
            --body-file "$RUNNER_TEMP/bench-report.md"