set-target-milestone.yml

name: Add milestone to pull requests
on:
  # Only run when a PR is closed
  pull_request:
    types:
      - closed

jobs:
  add_milestone_to_pr:
    # Only run if the PR was closed due to a merge
    if: github.event.pull_request.merged == true
    name: Add milestone to merged pull requests
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v3
        # Include all history and tags
        with:
          fetch-depth: 0
      - uses: actions/setup-python@v4
        name: Install Python
        with:
          python-version: '3.8'
      - name: Get target milestone
        id: milestones
        run: |
          pip install -U pip
          pip install packaging
          scripts/get-target-milestone.py
      - name: Update Pull Request
        if: steps.milestones.outputs.milestone != null
        uses: actions/github-script@v6.4.1
        with:
          github-token: ${{secrets.GITHUB_TOKEN}}
          script: |
            const title = "${{ steps.milestones.outputs.milestone }}";

            const milestones = await github.rest.issues.listMilestones({
              owner: context.repo.owner,
              repo: context.repo.repo,
              state: "open",
            });

            let milestone = milestones.data.find( (m) => m.title == title );
            if (milestone === undefined) {
              milestone = await github.rest.issues.createMilestone({
                owner: context.repo.owner,
                repo: context.repo.repo,
                title: title,
              });
            }

            await github.rest.issues.update({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: ${{ github.event.pull_request.number }},
              milestone: milestone.number,
            });