treefmt.yml

name: Check formatting with treefmt

on:
  [push, pull_request]

jobs:
  treefmt:
    runs-on: ubuntu-latest
    steps:
    - uses: cachix/install-nix-action@v22
    - uses: actions/checkout@v3
    - id: files
      uses: tj-actions/changed-files@v44
    - name: Run treefmt
      run: nix fmt
    - name: Check diff
      run: |
        unformatted_touched=()
        unformatted_untouched=()
        while IFS= read -r unformatted_file; do
          matched=
          for changed_file in ${{ steps.files.outputs.all }}; do
            if [[ "$changed_file" == "$unformatted_file" ]]; then
              unformatted_touched+=("$unformatted_file")
              matched=1
              break
            fi
          done
          if [[ -z "$matched" ]]; then
            unformatted_untouched+=("$unformatted_file")
          fi
        done <<< "$(git diff --name-only)"

        if (( ${#unformatted_untouched[@]} )); then
          echo "These files are not formatted, but out of scope of this PR:"
          printf '%s\n' "${unformatted_untouched[@]}"
        fi

        if (( ${#unformatted_touched[@]} )); then
          echo "These files are created/edited but not formatted:"
          printf '%s\n' "${unformatted_touched[@]}"
          exit 1
        fi