Instead of using a "discoveryLoading" action, return true so it can

bubble up itself.

app/assets/javascripts/discourse/controllers/discovery/categories.js.es6

@@ -13,7 +13,10 @@ export default DiscoveryController.extend({
       // Don't refresh if we're still loading
       if (this.get('controllers.discovery.loading')) { return; }
 
-      this.send('discoveryLoading');
+      // If we `send('loading')` here, due to returning true it bubbles up to the
+      // router and ember throws an error due to missing `handlerInfos`.
+      // Lesson learned: Don't call `loading` yourself.
+      this.set('controllers.discovery.loading', true);
       Discourse.CategoryList.list('categories').then(function(list) {
         self.set('model', list);
         self.send('loadingComplete');

app/assets/javascripts/discourse/controllers/discovery/topics.js.es6

@@ -42,7 +42,10 @@ var controllerOpts = {
       // Don't refresh if we're still loading
       if (this.get('controllers.discovery.loading')) { return; }
 
-      this.send('discoveryLoading');
+      // If we `send('loading')` here, due to returning true it bubbles up to the
+      // router and ember throws an error due to missing `handlerInfos`.
+      // Lesson learned: Don't call `loading` yourself.
+      this.set('controllers.discovery.loading', true);
       Discourse.TopicList.find(filter).then(function(list) {
         self.setProperties({ model: list, selected: [] });
 

app/assets/javascripts/discourse/routes/build-category-route.js.es6

@@ -5,10 +5,6 @@ export default function(filter, params) {
   return Discourse.Route.extend({
     queryParams: queryParams,
 
-    beforeModel: function(transition) {
-      transition.send('discoveryLoading');
-    },
-
     model: function(modelParams) {
       return Discourse.Category.findBySlug(modelParams.slug, modelParams.parentSlug);
     },
@@ -89,7 +85,6 @@ export default function(filter, params) {
       });
 
       this.controllerFor('search').set('searchContext', model.get('searchContext'));
-      this.controllerFor('discovery').send('loadingComplete');
       this.set('topics', null);
 
       this.openTopicDraft(topics);

app/assets/javascripts/discourse/routes/build-topic-route.js.es6

@@ -17,8 +17,7 @@ export default function(filter, extras) {
   return Discourse.Route.extend({
     queryParams: queryParams,
 
-    beforeModel: function(transition) {
+    beforeModel: function() {
-      transition.send('discoveryLoading');
       this.controllerFor('navigation/default').set('filterMode', filter);
     },
 
@@ -61,7 +60,6 @@ export default function(filter, extras) {
 
       this.openTopicDraft(model);
       this.controllerFor('navigation/default').set('canCreateTopic', model.get('can_create_topic'));
-      this.controllerFor('discovery').send('loadingComplete');
     },
 
     renderTemplate: function() {

app/assets/javascripts/discourse/routes/discovery_route.js

@@ -19,12 +19,13 @@ Discourse.DiscoveryRoute = Discourse.Route.extend(Discourse.ScrollTop, Discourse
   },
 
   actions: {
-    discoveryLoading: function() {
+    loading: function() {
       var controller = this.controllerFor('discovery');
 
       // If we're already loading don't do anything
       if (controller.get('loading')) { return; }
       controller.set('loading', true);
+      return true;
     },
 
     loadingComplete: function() {