default.nix

{ mkDerivation, aeson, base, bytestring, directory, either
, engine-io, engine-io-wai, http-types, js-jquery, lucid, random
, servant, servant-client, servant-docs, servant-jquery
, servant-lucid, servant-server, socket-io, stdenv, text, time
, transformers, wai, wai-extra, warp
}:
mkDerivation {
  pname = "servant-examples";
  version = "0.4.1";
  src = ./.;
  isLibrary = false;
  isExecutable = true;
  buildDepends = [
    aeson base bytestring directory either engine-io engine-io-wai
    http-types js-jquery lucid random servant servant-client
    servant-docs servant-jquery servant-lucid servant-server socket-io
    text time transformers wai wai-extra warp
  ];
  homepage = "http://haskell-servant.github.io/";
  description = "Example programs for servant";
  license = stdenv.lib.licenses.bsd3;
}

error

error: anonymous function at /Users/bmartin/Work/opensrc/servant/servant-examples/default.nix:1:1 called without required argument ‘engine-io-wai’, at /usr/local/nix/nixpkgs/lib/customisation.nix:58:12
(use ‘--show-trace’ to show detailed location information)

shell.nix

let
  pkgs = import <nixpkgs> {};

  haskellPackages = pkgs.haskell-ng.packages.ghc7101.override {
    overrides = self: super: {
      servant-examples = self.callPackage ./. {};
    };
  };

in haskellPackages.servant-examples.env