title: Angular injects "string:" before value in ng-options
body: <p>I have a <code>ng-options</code> list defined with a HTML select element such as:</p>
  
  <pre><code>&lt;select
      required="required"
      ng-model="vm.selectedOption"
      ng-options="item.name as item.label for item in vm.options"&gt;
  
      &lt;option value=""&gt;Select an option&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>This however results in the following HTML:</p>
  
  <pre><code>&lt;option value="string:VALUE" label="Option Name"&gt;Option Name&lt;/option&gt;
  </code></pre>
  
  <p>I am using Angular version 1.4.8, does anyone have a solution how to solve the <code>string:</code> issue or at least can explain to me why this is occurring? </p>
  
  <p>The <code>vm.options</code> array looks like this:</p>
  
  <pre><code>[
    {
      "name": "INFILL_AUTOMATIC",
      "label": "Automatic"
    },
    {
      "name": "INFILL_GRID",
      "label": "Grid"
    }
  ]
  </code></pre>
  
  <p>//EDIT:</p>
  
  <p>When logging <code>vm.selectedOption</code> I just see the correct value. So the <code>ng-model</code> does in fact have the correct value. But why is Angular giving the default <code>value</code> then this prefix, is it using this prefix to define the "type" for the <code>ng-model</code> or something?</p>