inverted-mixin-proposal.js

//app-config.js
define(function() {
  return {
    protos: {
      movieLister: {
        module: "movies/movie-lister",
        args: [
          "*movieFinder"
        ]
        mixin: {
          ref: "movieViewer",
          override: false
        }
      },
      movieViewer: {
        module: "movie/movie-"
      }
    }
  };
});

mixin-function.js

//mixin function
var mixin = function(toMix, mixWith, toMixId, override) {

  override = typeof override === "boolean" ? override : true;       
  
  for(var fn in mixWith) {
    if(typeof mixWith[fn] === "function" && 
      (!(fn in toMix) || (fn in toMix && override))) {
      (function(fn) {
        toMix[fn] = function() {
					return mixWith[fn].apply(mixWith, arguments);
				};
			})(fn);
		}
	}
	toMix["__" + toMixId + "__"] = mixWith;
};