nixpkgs/pkgs/applications/window-managers/xmonad/wrapper.nix

{ stdenv, ghcWithPackages, xmessage, makeWrapper, packages }:

let
xmonadEnv = ghcWithPackages (self: [ self.xmonad ] ++ packages self);
in stdenv.mkDerivation {
  pname = "xmonad-with-packages";
  inherit (xmonadEnv) version;

  nativeBuildInputs = [ makeWrapper ];

  buildCommand = ''
    install -D ${xmonadEnv}/share/man/man1/xmonad.1.gz $out/share/man/man1/xmonad.1.gz
    makeWrapper ${xmonadEnv}/bin/xmonad $out/bin/xmonad \
      --set XMONAD_GHC "${xmonadEnv}/bin/ghc" \
      --set XMONAD_XMESSAGE "${xmessage}/bin/xmessage"
  '';

  # trivial derivation
  preferLocalBuild = true;
  allowSubstitutes = false;
}