未添加重复芯片时触发验证事件

Question

当我尝试添加重复的芯片时，该组件会自动删除新添加的芯片，因为它不允许添加重复的芯片。

我需要触发一个事件，我可以依靠该事件查看用户无法添加重复筹码的验证消息

---

<div ng-controller="BasicDemoCtrl as ctrl" layout="column"
     ng-cloak="" class="chipsdemoBasicUsage" ng-app="MyApp">

  <md-content class="md-padding" layout="column">

     <h2 class="md-title">Make chips editable.</h2>

       <md-chips ng-model="ctrl.editableFruitNames" readonly="ctrl.readonly"
                 md-removable="ctrl.removable" md-enable-chip-edit="true"
                 input-aria-label="Fruit names">
       </md-chips>
       <em ng-if="if chips duplicated(the condition which I need)">You have 
        added a duplicated chip</em>

尝试添加重复的芯片..重复的芯片将被自动删除，而没有任何验证消息https://codepen.io/aRagabCs/pen/OYXwEx