enforce-semver.yml

name: Check if SemVer label is set

on:
  pull_request:
    # cf: https://github.com/yogevbd/enforce-label-action#enforce-pr-labels
    types: [labeled, unlabeled, opened, edited, synchronize]

env:
  # see: https://github.com/pixiv/charcoal/issues/labels
  SEMVER_LABELS: '["major", "minor", "patch", "beta"]'

jobs:
  enforce-semver:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/github-script@v6
        with:
          script: |
            const { issue, repo } = context

            const { data: pull } = await github.rest.issues.get({
              issue_number: issue.number,
              owner: repo.owner,
              repo: repo.repo,
            })

            const labels = pull.labels.map(({ name }) => name)
            const SEMVER_LABELS = JSON.parse(process.env.SEMVER_LABELS)

            const result = new Set()
            for (const label of labels) {
              for (const semver of SEMVER_LABELS) {
                if (label !== semver) {
                  continue
                }

                result.add(semver)
              }
            }

            switch (result.size) {
              case 1: {
                const [next] = result.values()
                console.log(`Merging this PR will be a ${next} release`)
                break
              }

              case 0: {
                throw new Error(`One of semver labels (${SEMVER_LABELS}) must be set`)
              }

              default: {
                throw new Error(`Do not set multiple semver labels: ${labels}`)
              }
            }