release-milestone.yaml

name: 'Release Milestone Check'
on:
  pull_request_target:
    types:
    - opened
    - reopened
    - synchronize
    - labeled
    - unlabeled

jobs:
  check-release-milestone:
    name: Check Release Milestone
    runs-on: ubuntu-latest
    steps:
    - uses: actions/checkout@v2
      with:
        path: './'

    - id: version
      run: |
        echo "::set-output name=version::$(cat ./VERSION)"

    - name: Block merge if release milestone is missing
      uses: actions/github-script@v4
      with:
        github-token: ${{ secrets.GITHUB_TOKEN }}
        script: |
          const nextMinorRegex = /^(v[0-9]+\.[0-9]+)\.0-dev/gmi;

          let match = nextMinorRegex.exec('${{ steps.version.outputs.version }}');
          if (match == null) {
            core.info('VERSION does not indicate that the next version is a new minor release - skipping check');
            return;
          }
          const nextMinorVersion = match[1];

          const milestones = await github.issues.listMilestones({
            owner: context.repo.owner,
            repo: context.repo.repo,
            state: 'open',
            sort: 'due_on',
            direction: 'desc'
          });

          let milestoneForNextMinorReleaseFound = false;

          for (const milestone of milestones.data) {
            if (milestone.title != nextMinorVersion) {
              continue;
            }

            // milestone found, check if PR is associated
            milestoneForNextMinorReleaseFound = true;

            if (context.payload.pull_request.milestone == null) {
              core.setFailed('Milestone for next minor release ' + nextMinorVersion + ' found, however, PR is not milestoned for it. Merge is not allowed.');
              return
            }
          }

          if (milestoneForNextMinorReleaseFound) {
            core.info('Milestone for next minor release ' + nextMinorVersion + ' found and PR is milestoned for it. Merge is allowed.');
          } else {
            core.info('Milestone for next minor release ' + nextMinorVersion + ' not found. Merge is allowed.');
          }