FIX: N+1 query on /categories page

app/models/category_list.rb

@@ -55,7 +55,7 @@ class CategoryList
     # Find a list of all categories to associate the topics with
     def find_categories
       @categories = Category
-                        .includes(:featured_users, subcategories: [:topic_only_relative_url])
+                        .includes(:featured_users, :topic_only_relative_url, subcategories: [:topic_only_relative_url])
                         .secured(@guardian)
 
       if @options[:parent_category_id].present?

app/serializers/basic_category_serializer.rb

@@ -28,6 +28,7 @@ class BasicCategorySerializer < ApplicationSerializer
   def can_edit
     true
   end
+
   def include_can_edit?
     scope && scope.can_edit?(object)
   end

app/serializers/category_detailed_serializer.rb

@@ -26,7 +26,7 @@ class CategoryDetailedSerializer < BasicCategorySerializer
   end
 
   def include_displayable_topics?
-    return displayable_topics.present?
+    displayable_topics.present?
   end
 
   def description_excerpt

app/serializers/listable_topic_serializer.rb

@@ -23,6 +23,7 @@ class ListableTopicSerializer < BasicTopicSerializer
              :notification_level
 
   has_one :last_poster, serializer: BasicUserSerializer, embed: :objects
+
   def include_last_poster?
     object.include_last_poster
   end