Custom angular form validation (Angular 1.2 vs 1.3)

userCtrl.js

/**
 * Angular 1.2
 * Helper method for Signup and Update. Checks if email or username of user exists per GET request.
 * Sets custom validation: 'exists' to true or false.
 * @example
 *   <input type="email" name="email" ng-model="user.email" ng-change="checkIfExists(form.email)" />
 */
var timeout = false;
$scope.checkIfExists = function(input) {
  if(!input.$viewValue) { return; }
  var params = {};
  params[input.$name] = input.$viewValue;

  input.$setValidity('exists', true);

  if(timeout) {
    $timeout.cancel(timeout);
  }
  timeout = $timeout(function () {
    User.exists(params, function(data) {
      if(data.exists) {
        input.$setValidity('exists', false);
      }
    });
  }, 500);
};

userValidatorDrct.js

/**
 * Angular 1.3
 * Helper method for Signup and Update. Checks if email or username of user exists per GET request.
 * Sets custom validation: 'exists' to true or false.
 * @example
 *   <input type="email" name="email" ng-model="user.email" user-exists-validator />
 */
app.directive('userExistsValidator', function($q, User) {
  return {
    require : 'ngModel',
    link: function($scope, element, attrs, ngModel) {
      ngModel.$asyncValidators.exists = function(value) {
        var defer = $q.defer();
        var params = {};
        params[attrs.name] = value;

        User.exists(params, function(data) {
          if(data.exists) {
            defer.reject();
          } else {
            defer.resolve();
          }
        });
        return defer.promise;
      };
    }
  };
});