python-bench-regression.yml

name: CI / Benchmarks / Regression

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

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

jobs:
  head:
    name: "Bench head"
    uses: ./.github/workflows/python-bench.yml
    with:
      suffix: head
      quick: true
      repeats: "5"
      warmup_loops: "1"
      artifact_name: pathable-bench-pr-head

  compare:
    name: "Bench compare (PR vs baseline)"
    runs-on: ubuntu-latest
    needs: head
    env:
      BENCH_TOLERANCE: "0.20"
    steps:
      - uses: actions/checkout@v6

      - name: Download head benchmark results
        uses: actions/download-artifact@v8
        with:
          name: pathable-bench-pr-head
          path: reports

      - name: Restore baseline cache
        id: baseline-cache
        uses: actions/cache/restore@v5
        with:
          path: |
            reports/bench-parse.baseline.json
            reports/bench-lookup.baseline.json
          key: bench-baseline-py3.12-${{ github.event.pull_request.base.sha }}
          restore-keys: |
            bench-baseline-py3.12-

      - name: Ensure baseline exists
        shell: bash
        run: |
          set -euo pipefail
          if [[ -f reports/bench-parse.baseline.json && -f reports/bench-lookup.baseline.json ]]; then
            exit 0
          fi
          echo "Baseline benchmark cache not found for this repository." >&2
          echo "Run the baseline workflow on master at least once to populate cache." >&2
          exit 1

      - name: Compare parse benchmark
        shell: bash
        run: |
          python tests/benchmarks/compare_results.py \
            --baseline reports/bench-parse.baseline.json \
            --candidate reports/bench-parse.head.json \
            --tolerance "$BENCH_TOLERANCE"

      - name: Compare lookup benchmark
        shell: bash
        run: |
          python tests/benchmarks/compare_results.py \
            --baseline reports/bench-lookup.baseline.json \
            --candidate reports/bench-lookup.head.json \
            --tolerance "$BENCH_TOLERANCE"

      - name: Upload comparison inputs
        uses: actions/upload-artifact@v7
        with:
          name: pathable-bench-pr-results
          path: reports/bench-*.json