shell.nix

let
  pkgs = import <nixpkgs> {};
  stdenv = pkgs.stdenv;
  top-level = import ./top-level.nix { haskellPackages = pkgs.haskellPackages;
                                       dontCheck = pkgs.haskell.lib.dontCheck;
                                       testTopLevel = false; };
in {
  haskellEnv = stdenv.mkDerivation {
    name = "haskell-env";
    version = "1.1.1.1";
    src = ./.;
    buildInputs = [ pkgs.cabal-install top-level.frank.env ];
  };
}

top-level.nix

let pkgs = import <nixpkgs> { };
in
{ haskellPackages ? pkgs.haskellPackages,
  dontCheck ? pkgs.haskell.lib.dontCheck,
  testTopLevel ? false, }:
let deps = import ../deps/deps.nix { inherit haskellPackages; inherit dontCheck; };
    test = if testTopLevel then x: x else dontCheck;
in rec {
  frank = test (haskellPackages.callPackage ../frank/frank.nix deps);
  backend-service = test (haskellPackages.callPackage ../backend/service/service.nix (deps // { inherit frank; }));
}