building EM

Gemfile

source 'https://rubygems.org' do
  gem 'eventmachine'
end

shell.nix

with (import (fetchGit {
  url = https://github.com/NixOS/nixpkgs-channels;
  ref = "nixpkgs-unstable";
  rev = "255a833e841628c0b834575664eae373e28cdc27";
}) {});
let
  ruby = ruby_2_5;
  bundler = pkgs.bundler.override { inherit ruby; };
  bundix = pkgs.bundix.override { inherit bundler; };
  env = if builtins.pathExists ./gemset.nix
          then
            let gems = bundlerEnv {
              inherit ruby;
              name = "test-gems";
              gemdir = ./.;
            }; in [ gems.wrappedRuby (lowPrio gems) ]
          else builtins.trace "to get your gems, please run bundix -l" [];
in stdenv.mkDerivation {
  name = "test-shell";
  buildInputs = [
    bundler
    bundix
  ] ++ env;
}