anchor.diff:  # Require the optional to be enabled until upstream fixes or removes the configure flag
   assert expat != null;
   
  +with stdenv.lib;
   stdenv.mkDerivation rec {
     name = "wayland-${version}";
     version = "1.7.0";
  
positive.code:   meta = {
      description = "Reference implementation of the wayland protocol";
      homepage    = http://wayland.freedesktop.org/;
      license     = lib.licenses.mit;
      platforms   = lib.platforms.linux;
      maintainers = with lib.maintainers; [ codyopel wkennington ];
    };
  
    passthru.version = version;
  
negative.code: { stdenv, fetchurl, pkgconfig
  , libffi, docbook_xsl, doxygen, graphviz, libxslt, xmlto
  , expat ? null # Build wayland-scanner (currently cannot be disabled as of 1.7.0)
  }:
  