check-pr-labels.yml

name: PR needs one allowed label

on:
  pull_request:
    types: [opened, synchronize, labeled, unlabeled]

jobs:
  check-pr-labels:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout code
        uses: actions/checkout@v4

      - name: Install dependencies
        run: |
          sudo apt-get install -y jq
          pip install yq # Tool to parse YAML files

      - name: Read allowed labels from .github/release.yml
        id: read_labels
        run: |
          # Will read allowed PR labels from .github/release.yml file.
          allowed_labels=$(yq '.changelog.categories[].labels[] | select(. != "*")' .github/release.yml)
          allowed_labels=$(echo "$allowed_labels" | tr -d '"')

          if [ -z "$allowed_labels" ]; then
            echo "Error: No allowed labels found in .github/release.yml."
            exit 1
          fi

          echo "Allowed labels from release.yml:"
          echo "$allowed_labels"
          echo "---"

          # Convert to an array of strings
          allowed_labels=$(echo "$allowed_labels" | tr '\n' ';')

          # set the allowed labels in the GITHUB_OUTPUT
          echo "ALLOWED_LABELS=${allowed_labels}" >> "$GITHUB_OUTPUT"

      - name: Check PR Labels
        id: check_labels
        env:
          ALLOWED_LABELS: ${{ steps.read_labels.outputs.ALLOWED_LABELS }}
        run: |
          # Will check that PR has exactly one of the allowed labels.
          if [ -z "$ALLOWED_LABELS" ]; then
            echo "Error: No allowed labels found from .github/release.yml. Configuration issue."
            exit 1
          fi

          pr_labels=$(jq -r '.pull_request.labels[].name' $GITHUB_EVENT_PATH)

          if [ -z "$pr_labels" ]; then
            echo "Error: PR has no labels. Please add one of the allowed labels: $ALLOWED_LABELS"
            exit 1
          fi

          echo "Labels on PR:"
          echo "$pr_labels"
          echo "---"

          # Convert the string an to an array of strings
          IFS=';' read -r -a allowed_labels_list <<< "$ALLOWED_LABELS"

          count=0
          for label in "${allowed_labels_list[@]}"; do
            echo "Checking allowed label \"$label\" in PR labels."
            if echo "$pr_labels" | grep -q "^$label$"; then
              count=$((count + 1))
            fi
          done

          echo "Allowed label count: $count"

          if [ "$count" -ne 1 ]; then
            echo "Error: PR must have exactly one of the allowed labels: $ALLOWED_LABELS"
            exit 1
          fi