pr-title.yml

name: Pull Request Title

on:
  pull_request_target:
    types: [opened, edited, reopened, synchronize]
    branches:
      - "master"

concurrency:
  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
  cancel-in-progress: true

jobs:
  conventional-commit:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: write
    env:
      # Shared between both steps. Must stay portable across bash ERE and JS
      # regex (no lookarounds, named groups, or other JS-only features).
      # Revert PRs always get semver-patch regardless of the original change's type.
      PR_TITLE_PATTERN: '^(revert(!)?: .+|(feat|fix|docs|style|refactor|perf|test|bench|build|ci|chore)(\(([^)]+)\))?(!)?: .+)'
    steps:
      - name: Checkout base revision
        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
        with:
          ref: ${{ github.event.pull_request.base.sha }}
          persist-credentials: false

      - name: Auto-rename GitHub revert title to Conventional Commit
        id: rename
        if: startsWith(github.event.pull_request.title, 'Revert "')
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          script: |
            const title = context.payload.pull_request.title
            const m = title.match(/^Revert "(.+)"$/)
            if (!m) return
            const newTitle = `revert: ${m[1]}`
            core.notice(`Auto-renaming PR title to: ${newTitle}`)
            await github.rest.pulls.update({
              ...context.repo,
              pull_number: context.payload.pull_request.number,
              title: newTitle,
            })
            core.setOutput('renamed', 'true')

      - name: Validate PR title and release-note context
        if: >-
          steps.rename.outputs.renamed != 'true' &&
          (github.event.action != 'edited' || github.event.changes.title != null)
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          script: |
            const pullRequest = context.payload.pull_request
            const title = pullRequest.title || ''
            const match = title.match(new RegExp(process.env.PR_TITLE_PATTERN))
            if (!match) {
              core.setFailed('PR title does not follow Conventional Commits format.')
              return
            }
            core.info(`PR title OK: ${title}`)

            const type = match[3]
            const changedFiles = await github.paginate(github.rest.pulls.listFiles, {
              ...context.repo,
              pull_number: pullRequest.number,
              per_page: 100,
            })
            const files = []
            const { appendChangedPaths, isInternalOnly } = require('./scripts/release/changelog')
            appendChangedPaths(files, changedFiles)
            if (/^(?:feat|fix|perf|docs)$/.test(type) && isInternalOnly(files)) {
              core.setFailed(`PR title type "${type}" is public, but every changed file is internal. ` +
                'Use test, bench, ci, or chore.')
            }

      - name: Sync labels with PR title
        if: steps.rename.outputs.renamed != 'true'
        uses: actions/github-script@3a2844b7e9c422d3c10d287c895573f7108da1b3 # v9.0.0
        with:
          script: |
            const pattern = new RegExp(process.env.PR_TITLE_PATTERN)
            const parse = (title) => {
              const m = (title || '').match(pattern)
              if (!m) return {}
              const isRevert = !m[3]
              return {
                type: isRevert ? 'revert' : m[3],
                scope: isRevert ? undefined : m[5],
                breaking: isRevert ? m[2] === '!' : m[6] === '!',
              }
            }

            // Reverts are always semver-patch regardless of the original change's type.
            const semverFor = ({ type, breaking }) => {
              if (!type) return undefined
              if (breaking) return 'semver-major'
              if (type === 'feat') return 'semver-minor'
              return 'semver-patch'
            }

            const pr = context.payload.pull_request
            const next = parse(pr.title)

            // Prefetch all existing repo labels once to avoid per-label API calls.
            const repoLabels = new Set()
            for await (const page of github.paginate.iterator(github.rest.issues.listLabelsForRepo, { ...context.repo, per_page: 100 })) {
              for (const label of page.data) repoLabels.add(label.name)
            }

            // Returns the set of labels derived from a parsed title.
            // Type and scope are only added if they exist in the repo.
            const titledLabels = (parsed) => {
              const labels = new Set()
              if (!parsed.type) return labels
              if (repoLabels.has(parsed.type)) labels.add(parsed.type)
              if (parsed.scope && repoLabels.has(parsed.scope)) labels.add(parsed.scope)
              const semver = semverFor(parsed)
              if (semver) labels.add(semver)
              return labels
            }

            const nextLabels = titledLabels(next)
            const current = new Set((pr.labels || []).map(l => l.name))

            // When the title changes, remove labels from the old title that no
            // longer apply so stale type/scope/semver labels don't linger.
            const titleChanged = context.payload.action === 'edited' &&
              context.payload.changes?.title?.from != null
            const toRemove = new Set()
            if (titleChanged) {
              const prev = parse(context.payload.changes.title.from)
              for (const label of titledLabels(prev)) {
                if (!nextLabels.has(label)) toRemove.add(label)
              }
            }

            const desired = new Set([...current].filter(l => !toRemove.has(l)))
            for (const label of nextLabels) desired.add(label)

            const unchanged = current.size === desired.size && [...current].every(l => desired.has(l))
            if (!unchanged) {
              await github.rest.issues.setLabels({
                ...context.repo,
                issue_number: pr.number,
                labels: [...desired],
              })
            }