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@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
        with:
          # pull_request_target checks out the base branch by default
          ref: refs/pull/${{ github.event.pull_request.number }}/merge
      - name: Get Nixpkgs revision for nixfmt
        run: |
          # pin to a commit from nixpkgs-unstable to avoid e.g. building nixfmt
          # from staging
          # This should not be a URL, because it would allow PRs to run arbitrary code in CI!
          rev=$(jq -r .rev ci/pinned-nixpkgs.json)
          echo "url=https://github.com/NixOS/nixpkgs/archive/$rev.tar.gz" >> "$GITHUB_ENV"
      - uses: cachix/install-nix-action@8887e596b4ee1134dae06b98d573bd674693f47c # v26
        with:
          # explicitly enable sandbox
          extra_nix_config: sandbox = true
          nix_path: nixpkgs=${{ env.url }}
      - name: Install nixfmt
        run: "nix-env -f '<nixpkgs>' -iAP nixfmt-rfc-style"
      - name: Check that Nix files are formatted according to the RFC style
        # Each environment variable beginning with NIX_FMT_PATHS_ is a list of
        # paths to check with nixfmt.
        env:
          NIX_FMT_PATHS_BSD: pkgs/os-specific/bsd
          NIX_FMT_PATHS_MPVSCRIPTS: pkgs/applications/video/mpv/scripts
          # Format paths related to the Nixpkgs CUDA ecosystem.
          NIX_FMT_PATHS_CUDA: |-
            pkgs/development/cuda-modules
            pkgs/test/cuda
            pkgs/top-level/cuda-packages.nix
          NIX_FMT_PATHS_MAINTAINERS: |-
            maintainers/maintainer-list.nix
            maintainers/team-list.nix
          NIX_FMT_PATHS_K3S: |-
            nixos/modules/services/cluster/k3s
            nixos/tests/k3s
            pkgs/applications/networking/cluster/k3s
          NIX_FMT_PATHS_VSCODE_EXTS: pkgs/applications/editors/vscode/extensions
          NIX_FMT_PATHS_PHP_PACKAGES: pkgs/development/php-packages
          NIX_FMT_PATHS_BUILD_SUPPORT_PHP: pkgs/build-support/php
        # Iterate over all environment variables beginning with NIX_FMT_PATHS_.
        run: |
          unformattedPaths=()
          for env_var in "${!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
              unformattedPaths+=("${paths[@]}")
            fi
          done
          if (( "${#unformattedPaths[@]}" > 0 )); then
            echo "Some required Nix files are not properly formatted"
            echo "Please run the following in \`nix-shell\`:"
            echo "nixfmt ${unformattedPaths[*]@Q}"
            exit 1
          fi