nixpkgs/.github/workflows/check-nix-format.yml

# This file was copied mostly from check-maintainers-sorted.yaml.
# NOTE: Formatting with the RFC-style nixfmt command is not yet stable. See
# https://github.com/NixOS/rfcs/pull/166.
# Because of this, this action is not yet enabled for all files -- only for
# those who have opted in.
name: Check that Nix files are formatted

on:
  pull_request_target:
permissions:
  contents: read

jobs:
  nixos:
    runs-on: ubuntu-latest
    if: github.repository_owner == 'NixOS'
    steps:
      - uses: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b # v4.1.4
        with:
          # pull_request_target checks out the base branch by default
          ref: refs/pull/${{ github.event.pull_request.number }}/merge
      - uses: cachix/install-nix-action@8887e596b4ee1134dae06b98d573bd674693f47c # v26
        with:
          # explicitly enable sandbox
          extra_nix_config: sandbox = true
          # fix a commit from nixpkgs-unstable to avoid e.g. building nixfmt
          # from staging
          nix_path: nixpkgs=https://github.com/NixOS/nixpkgs/archive/4b455dc2048f73a79eb3713f342369ff58f93e0b.tar.gz
      - name: Install nixfmt
        run: "nix-env -f '<nixpkgs>' -iAP nixfmt-rfc-style"
      - name: Check that Nix files are formatted according to the RFC style
        # Each environment variable beginning with NIX_FMT_PATHS_ is a list of
        # paths to check with nixfmt.
        env:
          NIX_FMT_PATHS_BSD: pkgs/os-specific/bsd
          NIX_FMT_PATHS_MPVSCRIPTS: pkgs/applications/video/mpv/scripts
          # Format paths related to the Nixpkgs CUDA ecosystem.
          NIX_FMT_PATHS_CUDA: |
            pkgs/development/cuda-modules
            pkgs/test/cuda
            pkgs/top-level/cuda-packages.nix
          NIX_FMT_PATHS_VSCODE_EXTS: pkgs/applications/editors/vscode/extensions
          NIX_FMT_PATHS_PHP_PACKAGES: pkgs/development/php-packages
          NIX_FMT_PATHS_BUILD_SUPPORT_PHP: pkgs/build-support/php
        # Iterate over all environment variables beginning with NIX_FMT_PATHS_.
        run: |
          for env_var in "${!NIX_FMT_PATHS_@}"; do
            readarray -t paths <<< "${!env_var}"
            if [[ "${paths[*]}" == "" ]]; then
              echo "Error: $env_var is empty."
              exit 1
            fi
            echo "Checking paths: ${paths[@]}"
            if ! nixfmt --check "${paths[@]}"; then
              echo "Error: nixfmt failed."
              exit 1
            fi
          done