stackoverflow ng-message custom validation

<!-- begin snippet: js hide: false -->

<!-- language: lang-js -->

    var app = angular.module('app', ['ngMessages']);

    app.controller('myController', function($scope) {
      $scope.data = {};
    });

    app.directive('passwordFormatValidator', function() {
      return {
        require : 'ngModel',
        link : function(scope, element, attrs, ngModel) {
          ngModel.$parsers.push(function(value) {
            if(!value || value.length == 0) return;
            ngModel.$setValidity('digit', /[0-9]/.test(value)); 
            ngModel.$setValidity('case', /[A-Z]/.test(value) && /[a-z]/.test(value)); 
            ngModel.$setValidity('special', /[^a-z0-9 ]/i.test(value)); 
            return value;
          });
        }
      };
    });

<!-- language: lang-css -->

    .errors {
      color: red;
      font-size: 0.75em;
    }


<!-- language: lang-html -->

    <script src="//ajax.googleapis.com/ajax/libs/angularjs/1.4.7/angular.min.js"></script>
    <script src="//cdnjs.cloudflare.com/ajax/libs/angular.js/1.4.7/angular-messages.js"></script>

    <div ng-app='app' ng-controller="myController">
      <form name="form" novalidation>
        <div class="field">
          <label for="password">Enter new password:</label>
          <input type="password"
                 name="password"
                 ng-model="data.password"
                 ng-minlength="5"
                 ng-maxlength="30"
                 password-format-validator
                 required />

          <ng-messages for="form.password.$error" ng-show="form.password.$touched" multiple class="errors">
            <div ng-message="required">Password is required</div>
            <div ng-message-exp="['minlength', 'maxlength']">Password must be between 5 and 30 characters in length</div>
            <div ng-message="digit">Password must include a digit</div>
            <div ng-message="case">Password must include both upper and lower case characters</div>
            <div ng-message="special">Password must include a special character</div>
          </ng-messages>
        </div>
      </form>
    </div>

<!-- end snippet -->