nixos-servers/formatter.nix

{
  self,
  nixpkgs,
  treefmt-nix,
  flake-utils,
  pre-commit-hooks,
  ...
}:
flake-utils.lib.eachDefaultSystem (
  system: let
    pkgs = nixpkgs.legacyPackages.${system};
    treefmtEval = treefmt-nix.lib.evalModule pkgs ./treefmt.nix;
    treefmtWrapper = treefmtEval.config.build.wrapper;
  in {
    packages.formatter = treefmtWrapper;
    formatter = self.packages.${system}.formatter;
    checks.pre-commit-check = pre-commit-hooks.lib.${system}.run {
      src = ./.;
      hooks = {
        treefmt = {
          enable = true;
          package = treefmtWrapper;
        };
      };
    };
  }
)