custom_elixir.nix

{ mkDerivation }:

mkDerivation rec {
  version = "custom";
  rev = "e2c78e8ba948739768a335999e35a06d5eb5ad4b";
  sha256 = "0fl49cznksscb1m0n87h3bpfknxg5hxvwgny69r5f7lgvlzzd3k3";
  minimumOTPVersion = "20";
}

shell.nix

with import <nixpkgs> {};

let
  lib = pkgs.callPackage <nixpkgs/pkgs/development/beam-modules/lib.nix> {};

  elixir = lib.callElixir ./custom_elixir.nix { inherit rebar erlang; };

in

stdenv.mkDerivation {
  name = "libfoo-1.2.3";
  src = ./.;
  buildInputs = [ elixir ];
}