title: AngularJS field validation expressions don't seem to work in ng-show
body: <p>I'm struggling with AngularJS validation. Here's my <a href="http://sscce.org/" rel="nofollow">SSCCE</a> in HTML 5 (which, due to my server-side framework, is required to be valid XML):</p>
  
  <p><strong><a href="http://jsfiddle.net/abbDA/" rel="nofollow">View in JSFiddle</a></strong></p>
  
  <p><strong>HTML</strong></p>
  
  <pre><code>&lt;div ng-app=""&gt;
      &lt;form name="myForm" ng-controller="ValidationTest" novalidate="novalidate"&gt;
          &lt;input name="email" ng-model="myForm.email" type="email" required="required" /&gt;
          &lt;div&gt;
              Field:
              &lt;span ng-show="myForm.email.$valid"&gt;valid&lt;/span&gt;
              &lt;span ng-show="myForm.email.$invalid"&gt;invalid&lt;/span&gt;
              &lt;span ng-show="myForm.email.$pristine"&gt;pristine&lt;/span&gt;
              &lt;span ng-show="myForm.email.$dirty"&gt;dirty&lt;/span&gt;
          &lt;/div&gt;
          &lt;div&gt;
              Form:
              &lt;span ng-show="myForm.$valid"&gt;valid&lt;/span&gt;
              &lt;span ng-show="myForm.$invalid"&gt;invalid&lt;/span&gt;
              &lt;span ng-show="myForm.$pristine"&gt;pristine&lt;/span&gt;
              &lt;span ng-show="myForm.$dirty"&gt;dirty&lt;/span&gt;
          &lt;/div&gt;
      &lt;/form&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p><strong>CSS</strong></p>
  
  <pre><code>input.ng-valid {
      border-color: #0f0;
  }
  input.ng-invalid {
      border-color: #f00;
  }
  input.ng-pristine {
      background-color: #eef;
  }
  input.ng-dirty {
      background-color: #fee;
  }
  </code></pre>
  
  <p><strong>JavaScript</strong></p>
  
  <pre><code>function ValidationTest($scope) {}
  </code></pre>
  
  <p>When I run this scenario, the CSS classes applied to the form element correctly reflect its validation status, as do the ng-show directives for the form. However, the ng-show directives for the field start out correct (showing "invalid" and "pristine") but all disappear once I start typing in the field. As far as I can tell, I'm doing this as the <a href="http://docs.angularjs.org/guide/forms" rel="nofollow">documentation</a> indicates, so what's wrong?</p>