bench-compare.yml

name: Benchmark Comparison

on:
  pull_request:
    types: [opened, synchronize, reopened]

concurrency:
  group: bench-${{ github.head_ref }}
  cancel-in-progress: true

jobs:
  bench-compare:
    name: 'Benchmark Comparison'
    runs-on: ubuntu-latest
    permissions:
      pull-requests: write
      contents: read

    steps:
      - uses: actions/checkout@v6
        id: checkout
        with:
          # Full history so the script can git-archive the base branch.
          fetch-depth: 0
          # Use the PR head SHA so fork PRs resolve correctly
          # (github.head_ref is a branch name that only exists on the fork remote).
          ref: ${{ github.event.pull_request.head.sha }}

      - uses: wyvox/action-setup-pnpm@v3

      - name: Run benchmark comparison
        env:
          BENCH_JSON_OUTPUT: ${{ runner.temp }}/bench-results.json
        run: |
          set -o pipefail
          pnpm bench:compare | sed 's/\x1b\[[0-9;]*m//g' > "$RUNNER_TEMP/bench-output.txt"

      - name: Format PR comment
        if: always() && steps.checkout.outcome == 'success'
        env:
          BENCH_OUTPUT_FILE: ${{ runner.temp }}/bench-output.txt
          BENCH_JSON_OUTPUT: ${{ runner.temp }}/bench-results.json
          BENCH_JOB_SUCCESS: ${{ job.status == 'success' }}
        run: node scripts/format-bench-comment.mjs > "$RUNNER_TEMP/bench-comment.md"

      - name: Write job summary
        if: always() && steps.checkout.outcome == 'success'
        run: cat "$RUNNER_TEMP/bench-comment.md" >> "$GITHUB_STEP_SUMMARY"

      - name: Post PR comment
        if: always() && steps.checkout.outcome == 'success'
        uses: actions/github-script@v9
        with:
          script: |
            const fs = require('fs');
            const marker = '<!-- bench-compare -->';

            const body = fs.readFileSync(process.env.RUNNER_TEMP + '/bench-comment.md', 'utf8');

            const headFullName = context.payload.pull_request?.head?.repo?.full_name;
            const isFork = !headFullName || headFullName !== context.repo.owner + '/' + context.repo.repo;

            if (isFork) {
              core.info('PR is from a fork — skipping PR comment (results are in the job summary).');
              core.info('--- Comment body start ---');
              core.info(body);
              core.info('--- Comment body end ---');
            } else {
              const { data: comments } = await github.rest.issues.listComments({
                owner: context.repo.owner,
                repo: context.repo.repo,
                issue_number: context.issue.number,
              });

              const existing = comments.find(c => c.body.includes(marker));

              if (existing) {
                await github.rest.issues.updateComment({
                  owner: context.repo.owner,
                  repo: context.repo.repo,
                  comment_id: existing.id,
                  body,
                });
              } else {
                await github.rest.issues.createComment({
                  owner: context.repo.owner,
                  repo: context.repo.repo,
                  issue_number: context.issue.number,
                  body,
                });
              }
            }