Rare $animate RTE issue

[ThomasBurleson]

Discovered a RTE in angular-animate.js:

TypeError: Cannot read property 'add' of undefined
    at resolveElementClasses (http://localhost:8200/js/angular-animate.js:480:22)
    at http://localhost:8200/js/angular-animate.js:1028:27
    at http://localhost:8200/js/angular-animate.js:469:22
    at Scope.$get.Scope.$digest (http://ajax.googleapis.com/ajax/libs/angularjs/1.3.0-rc.4/angular.js:13391:36)
    at Scope.$get.Scope.$apply (http://ajax.googleapis.com/ajax/libs/angularjs/1.3.0-rc.4/angular.js:13603:24)
    at http://ajax.googleapis.com/ajax/libs/angularjs/1.3.0-rc.4/angular.js:15334:36
    at completeOutstandingRequest (http://ajax.googleapis.com/ajax/libs/angularjs/1.3.0-rc.4/angular.js:4544:10)
    at http://ajax.googleapis.com/ajax/libs/angularjs/1.3.0-rc.4/angular.js:4849:7 angular.js:10734(anonymous function) angular.js:10734$get angular.js:7909$get.Scope.$digest angular.js:13393$get.Scope.$apply angular.js:13603(anonymous function) angular.js:15334completeOutstandingRequest angular.js:4544(anonymous function)

The argument cache === null in the call to resolveElementClasses(element, cache, state.active).

Can be fixed with || { add : [] , remove : [] } as shown below:

return cache.promise = runAnimationPostDigest(function(done) {
            var cache = element.data(STORAGE_KEY) || { add : [] , remove : [] };
            element.removeData(STORAGE_KEY);

            var state = element.data(NG_ANIMATE_STATE) || {};
            var classes = resolveElementClasses(element, cache, state.active);
            return !classes
              ? done()
              : performAnimation('setClass', classes, element, null, null, function() {
                  $delegate.setClass(element, classes[0], classes[1]);
                }, done);
          });

[ThomasBurleson]

The above fix is IMHO a bandaid the hides the real issue of why the incoming cache value is undefined.

[matsko]

There's a fix ready to go into angular master: angular/angular.js#8958

[ThomasBurleson]

@matsko - what about the safety check I have above. This idea is also mentioned in angular/angular.js#9049

[ThomasBurleson]

So this error manifests in Angular Material within Tabs.

Prior to this above fix mentioned my @matsko, here is the reasoning: if the element is removed before the digest kicks off then it leads to an error when a class based animation is run. This fix ensures that the animation will not run at all if the element does not have a parent element.