ci.yml

name: CI

on:
  push:
    branches:
      - master
  pull_request:
    branches:
      - master
  workflow_dispatch:

permissions:
  contents: read # to fetch code (actions/checkout)

# Cancel superseded runs of the same pull request; runs on master always finish.
concurrency:
  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
  cancel-in-progress: ${{ github.event_name == 'pull_request' }}

env:
  LATEST_GO_VERSION: "1.27"

  # https://github.com/actions/checkout/commit/df4cb1c069e1874edd31b4311f1884172cec0e10
  CHECKOUT_ACTION: &checkout_action actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6

  # https://github.com/actions/setup-go/commit/924ae3a1cded613372ab5595356fb5720e22ba16
  SETUP_GO_ACTION: &setup_go_action actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6

  # https://github.com/actions/cache/commit/55cc8345863c7cc4c66a329aec7e433d2d1c52a9
  CACHE_RESTORE_ACTION: &cache_restore_action actions/cache/restore@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0
  CACHE_SAVE_ACTION: &cache_save_action actions/cache/save@55cc8345863c7cc4c66a329aec7e433d2d1c52a9 # v6.1.0

  # https://github.com/codecov/codecov-action/commit/fb8b3582c8e4def4969c97caa2f19720cb33a72f
  CODECOV_ACTION: &codecov_action codecov/codecov-action@fb8b3582c8e4def4969c97caa2f19720cb33a72f # v7

jobs:
  test:
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
        # Each major Go release is supported until there are two newer major releases. https://golang.org/doc/devel/release.html#policy
        # Echo tests with last four major releases (unless there are pressing vulnerabilities)
        # As we depend on `golang.org/x/` libraries which only support the last 2 Go releases, we could have situations when
        # we derive from the last four major releases promise.
        go: ["1.25", "1.26", "1.27"]
    name: ${{ matrix.os }} @ Go ${{ matrix.go }}
    runs-on: ${{ matrix.os }}
    steps:
      - name: Checkout Code
        uses: *checkout_action

      - name: Set up Go ${{ matrix.go }}
        uses: *setup_go_action
        with:
          go-version: ${{ matrix.go }}
          cache: false

      # setup-go's built-in cache is keyed on go.sum only, so its entry is never refreshed and
      # soon holds little of the current build. Restore the latest cache saved for this job
      # instead, and save a new one after runs other than pull requests, which only restore.
      - name: Find Go Cache
        id: go-cache
        shell: bash
        run: |
          {
            echo "build=$(go env GOCACHE)"
            echo "mod=$(go env GOMODCACHE)"
            echo "key=go-${{ runner.os }}-${{ runner.arch }}-$(go env GOVERSION)-${{ github.job }}"
          } >> "$GITHUB_OUTPUT"

      - name: Restore Go Cache
        id: go-cache-restore
        uses: *cache_restore_action
        with:
          path: |
            ${{ steps.go-cache.outputs.build }}
            ${{ steps.go-cache.outputs.mod }}
          key: ${{ steps.go-cache.outputs.key }}-${{ github.sha }}
          restore-keys: ${{ steps.go-cache.outputs.key }}-

      - name: Run Tests
        run: go test -race --coverprofile=coverage.coverprofile --covermode=atomic ./...

      - name: Save Go Cache
        if: github.event_name != 'pull_request' && steps.go-cache-restore.outputs.cache-hit != 'true'
        uses: *cache_save_action
        with:
          path: |
            ${{ steps.go-cache.outputs.build }}
            ${{ steps.go-cache.outputs.mod }}
          key: ${{ steps.go-cache.outputs.key }}-${{ github.sha }}

      - name: Upload coverage to Codecov
        if: success() && matrix.go == env.LATEST_GO_VERSION && matrix.os == 'ubuntu-latest'
        uses: *codecov_action
        with:
          token:
          fail_ci_if_error: false

  benchmark:
    # Compares the pull request against its base branch. github.base_ref is only set for
    # pull_request events, so on other events both checkouts would be the same commit.
    if: github.event_name == 'pull_request'
    needs: test
    name: Benchmark comparison
    runs-on: ubuntu-latest
    steps:
      - name: Checkout Code (Previous)
        uses: *checkout_action
        with:
          ref: ${{ github.base_ref }}
          path: previous

      - name: Checkout Code (New)
        uses: *checkout_action
        with:
          path: new

      - name: Set up Go
        uses: *setup_go_action
        with:
          go-version: ${{ env.LATEST_GO_VERSION }}
          cache: false

      - name: Install Dependencies
        run: go install golang.org/x/perf/cmd/benchstat@latest

      # -benchtime=100ms instead of the default 1s keeps the job to a few minutes. The
      # comparison is advisory: it reports differences but never fails the build.
      - name: Run Benchmark (Previous)
        run: |
          cd previous
          go test -run="-" -bench=".*" -benchtime=100ms -count=8 ./... > benchmark.txt

      - name: Run Benchmark (New)
        run: |
          cd new
          go test -run="-" -bench=".*" -benchtime=100ms -count=8 ./... > benchmark.txt

      - name: Run Benchstat
        run: |
          benchstat previous/benchmark.txt new/benchmark.txt