asynchronous validator to return a promise but got 'undefined' instead - inside mddialog angular material

Question

I am using Anggular Material mdDialog to show a small Form inside a Dialog Box. I am calling a directive username-available to do asynchronous validation inside it.

dialog.tmpl.html:

<md-dialog aria-label="Save Scenario">
<form name="userForm" novalidate >

 <input style="display:inline-block" name="Name"  ng-model="SaveScenario.ScenarioName" ng-pattern="pattern"  
                   required  username-available ng-model-options="{ updateOn: 'blur' }">

</form>
</md-dialog>

app.js:

module.directive('usernameAvailable', function($timeout, $q,UserService) {
  return {
    restrict: 'A',
    require: 'ngModel',
    link: function(scope, elm, attr, ngModel) { 
      ngModel.$asyncValidators.usernameExists = function(modelValue, viewValue) {


        var currentValue = modelValue || viewValue;

        UserService.checkifScenarioNameExists(currentValue)
        .then(
                        function (d) 
                        {                            
                            console.log("the data object from promise is", d.data);
                            if ( d.data == true)
                            {
                                console.log("username exists");
                           //        deferred.resolve(d.data); 
                                   return $q.resolve(d.data);
                            }
                            else
                            {
                                console.log("username does not exist");
                                ngModel.$setValidity('usernameExists', false); 

                                  return $q.reject(d.data);
                            }


                        },
                        function (errResponse) {
                            console.error('The Promise was unsuccessfull');
                        }

                );

      };
    }
  } 
});

Here is how my Dialog Box looks like and the error are also displayed:

I think my syntax for returning a promise inside the directive is correct. I am not sure if it could be something with md-dialog. Can someone please help out why this error is happening??

Answer 1

As error states, expected asynchronous validator to return a promise. Inside validator, you missed return statement in front of your UserService usage.

return UserService.checkifScenarioNameExists(currentValue).then(...)