assign-milestone-on-close.yml

name: Assign Milestone on Close

env:
  MILESTONE_ID: ${{ vars.MILESTONE_ID }}

on:
  pull_request_target:
    types: [closed]

permissions:
  issues: write
  pull-requests: write
  actions: write

jobs:
  assign-milestone:
    runs-on: ubuntu-latest
    steps:
      - name: Early exit
        run: |
          if [ -z "$MILESTONE_ID" ]; then
            echo "MILESTONE_ID is not set. Exiting workflow."
            gh run cancel ${{ github.run_id }}
            gh run watch ${{ github.run_id }}
          fi
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
          GH_REPO: ${{ github.repository }}

      - name: Check if milestone is set
        id: check-milestone
        uses: actions/github-script@v7
        with:
          github-token: ${{secrets.GITHUB_TOKEN}}
          script: |
            const pr = context.payload.pull_request;
            if (!pr.milestone) {
              core.setOutput('milestoneNotSet', 'true');
            } else {
              core.setOutput('milestoneNotSet', 'false');
            }

      - name: Check merged
        id: check-done
        uses: actions/github-script@v7
        with:
          github-token: ${{secrets.GITHUB_TOKEN}}
          script: |
            if (context.payload.pull_request.merged === true) {
              core.setOutput('isDone', 'true');
            } else {
              core.setOutput('isDone', 'false');
            }

      - name: Assign default milestone
        if: steps.check-milestone.outputs.milestoneNotSet == 'true' && steps.check-done.outputs.isDone == 'true'
        uses: actions/github-script@v7
        with:
          github-token: ${{secrets.GITHUB_TOKEN}}
          script: |
            const prNumber = context.payload.pull_request.number;
            const repository = context.repo;
            await github.rest.issues.update({
              ...repository,
              issue_number: prNumber,
              milestone: process.env.MILESTONE_ID
            });