pr-title-checker.yml

name: PR Title Checker

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

permissions:
  contents: read # allow checkout of the repo config by default
  pull-requests: read # allow PR metadata reads by default

jobs:
  check:
    runs-on: ubuntu-latest
    name: pr-title-checker
    permissions:
      contents: read # checkout .github/pr-title-checker-config.json
      pull-requests: read # read PR title metadata from the event/CLI
      issues: write # create/update the Invalid PR Title label on the PR issue
    steps:
      - name: Checkout repository
        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # pinned from v6.0.2
        with:
          persist-credentials: false

      - name: Validate PR title
        env:
          GH_TOKEN: ${{ github.token }}
          PR_NUMBER: ${{ github.event.pull_request.number }}
          PR_TITLE: ${{ github.event.pull_request.title }}
        run: |
          set -euo pipefail

          config=.github/pr-title-checker-config.json
          if [ ! -f "$config" ]; then
            echo "::error::PR title checker config is missing at $config."
            exit 1
          fi

          read_config_value() {
            local query=$1
            local name=$2
            local value
            if ! value=$(jq -er "$query" "$config"); then
              echo "::error::Failed to read $name from $config."
              exit 1
            fi
            if [ -z "$value" ] || [ "$value" = "null" ]; then
              echo "::error::$name in $config must be non-empty."
              exit 1
            fi
            printf '%s' "$value"
          }

          regexp=$(read_config_value '.CHECKS.regexp' 'CHECKS.regexp')
          label=$(read_config_value '.LABEL.name' 'LABEL.name')
          color=$(read_config_value '.LABEL.color' 'LABEL.color')
          failure=$(read_config_value '.MESSAGES.failure' 'MESSAGES.failure')

          if [[ "$PR_TITLE" =~ $regexp ]]; then
            gh pr edit "$PR_NUMBER" --remove-label "$label" >/dev/null 2>&1 || true
            exit 0
          fi

          gh label create "$label" --color "$color" --force >/dev/null 2>&1 || true
          gh pr edit "$PR_NUMBER" --add-label "$label" >/dev/null 2>&1 || true
          echo "::error::$failure"
          exit 1