Ember.computed.apply() shared getter/setter

Beginning with Ember 1.12, the below code block generates a deprecation warning because of changes to encourage using distinct getters and setters. I understand the concept, but I'm not sure how to refactor something that uses Ember.computed.apply() in such a way that these deprecation warning are resolved.

var args = this.constructor.primaryKeys.concat(function(_, setValue) {
  var keyNames = this.constructor.primaryKeys;
  if (setValue === undefined) {
    var key, value;
    for (var i = 0; i < keyNames.length; i++) {
      key   = keyNames[i];
      value = this.get(key);

      if (!Ember.isNone(value)) {
        return value;
      }
    }
  } else {
    if (this.get('primaryKey') !== setValue) {
      this.set(keyNames[0], setValue);
    }
    return setValue;
  }
});
var primaryKey = Ember.computed.apply(Ember, args);

Twiddle demonstrating the problem