anchor.diff:  , withRiak ? false
   , withElixir ? false, elixir
   , withIconv ? true
  -, withLager ? true
   , withTools ? false
   , withRedis ? false
   }:
  
positive.code:       (lib.enableFeature withRiak "riak")
        (lib.enableFeature withElixir "elixir")
        (lib.enableFeature withIconv "iconv")
        (lib.enableFeature withLager "lager")
        (lib.enableFeature withTools "tools")
        (lib.enableFeature withRedis "redis")
      ] ++ lib.optional withSqlite "--with-sqlite3=${sqlite}";
  
negative.code: 
    meta = {
      description = "Open-source XMPP application server written in Erlang";
      license = lib.licenses.gpl2;
      homepage = http://www.ejabberd.im;
      platforms = lib.platforms.linux;
      maintainers = [ lib.maintainers.sander lib.maintainers.abbradar ];
    };
  }
  