validate-frontmatter.yml

name: Validate-Frontmatter

on:
  pull_request:
    branches: [ main ]

  workflow_dispatch:

jobs:
  validate-frontmatter:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      issues: write
      repository-projects: read
      pull-requests: write

    steps:
      # Step 1: Check out the source code of the pull request.
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0
          token: ${{ secrets.GITHUB_TOKEN }}
          ref: ${{ github.event.pull_request.head.ref }}
          repository: ${{ github.event.pull_request.head.repo.full_name }}

      # Step 2: Set up the Node.js environment.
      - uses: actions/setup-node@v4

      # Step 3: Get the list of changed files in the PR
      - name: Get changed files
        id: get_changed
        if: ${{ github.event_name == 'pull_request' }}
        run: |
          echo "changed=$(git diff --name-only $(git merge-base origin/main HEAD) HEAD)" | paste -sd "," - >> $GITHUB_ENV
          echo "pr_owner=${{ github.event.pull_request.user.login }}" >> $GITHUB_ENV

      # Step 4: Check Markdown files for valid frontmatter
      - name: Lint Frontmatter
        uses: mathiasvr/command-output@v1
        id: check_markdown
        with:
          run: |
            cd scripts/frontmatter-validator
            npm install --silent
            node frontmatter-validator.js '${{ env.changed }}'

      # Step 5: Write workflow job summary if the previous step failed
      - name: Add Job Summary
        if: failure()
        run: |
          echo "Hi @$pr_owner," >> $GITHUB_STEP_SUMMARY
          echo "${{ steps.check_markdown.outputs.stdout }}" >> $GITHUB_STEP_SUMMARY

      # Step 6: Leave a comment if the validation has failed and if it's not a PR from a fork
      - name: Comment on PR
        if: failure() && github.event.pull_request.head.repo.fork == false
        uses: mshick/add-pr-comment@v2
        with:
          message: |
            Hi @${{ env.pr_owner }},
            ${{ steps.check_markdown.outputs.stdout }}
            Please fix the Frontmatter in your Markdown files.
          repo-token: ${{ secrets.GITHUB_TOKEN }}
          repo-token-user-login: "github-actions[bot]"
          allow-repeats: true