[Nix-dev] ghc-mod depends on Wayland

[Andreas Herrmann]

Hello everyone,

Recently, I tried to install the ghc-mod package. I was surprised to see that nix-env intended to install a _large_ amount of dependencies down to quite unexpected ones such as Wayland.

I dug into the dependency tree:

    nix-store -qR --tree $(nix-instantiate -A haskellPackages.ghcMod '<nixpkgs>')

    /nix/store/0b7bmyslyidn7iq7bcmxzgxqa0wcd786-haskell-ghc-mod-ghc7.8.3-5.1.1.0-shared.drv
    +---/nix/store/gzgrizf2xw537hnnbycbnpbxzrwddxjw-emacs-24.4.drv
    |   +---/nix/store/lp9z54f5snvrdnvlih815m28lxb5080l-librsvg-2.36.4.drv
    |   |   +---/nix/store/l89khlm6piiilivpnx618w13cfqqj223-cairo-1.12.16.drv
    |   |   |   +---/nix/store/ib90dbdwvijmv44v7ij7ghs1md5nfrf2-mesa-noglu-10.2.6.drv
    |   |   |   |   +---/nix/store/gl09hmxv11fvsz2dkr6s6i5xsbvp2c55-wayland-1.6.0.drv


As it turns out this comes from Emacs and the problem is fixed with a simple package override:

    { pkgs }: {
      packageOverrides = self: with pkgs; {
        emacs = self.emacs.override { withX = false; withGTK = false; };
      }
    }


However, I'm wondering if this really is the intended default behavior for that package. Wouldn't it be better to have ghc-mod depend on a nox-emacs by default?

Best, Andreas