name: Check for modules that should use `prelude`

on: [pull_request]

jobs:
  check-prelude:
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v4
        with:
          # the default is to use a virtual merge commit between the PR and master: just use the PR
          ref: ${{ github.event.pull_request.head.sha }}
          sparse-checkout: src/Lean
      - name: Check Prelude
        run: |
          failed_files=""
          while IFS= read -r -d '' file; do
            if ! grep -q "^prelude$" "$file"; then
              failed_files="$failed_files$file\n"
            fi
          done < <(find src/Lean -name '*.lean' -print0)
          if [ -n "$failed_files" ]; then
            echo -e "The following files should use 'prelude':\n$failed_files"
            exit 1
          fi