FIX: hide category column in topic list only when the current category has no children

app/assets/javascripts/discourse/models/topic-list.js.es6

@@ -163,10 +163,9 @@ TopicList.reopenClass({
     return this.find(filter);
   },
 
-  // Sets `hideCategory` if all topics in the last have a particular category
+  // hide the category when it has no children
   hideUniformCategory(list, category) {
-    const hideCategory = !list.get('topics').any(function (t) { return t.get('category') !== category; });
-    list.set('hideCategory', hideCategory);
+    list.set('hideCategory', !category.get("has_children"));
   }
 
 });

app/models/category.rb

@@ -79,7 +79,7 @@ class Category < ActiveRecord::Base
 
   # permission is just used by serialization
   # we may consider wrapping this in another spot
-  attr_accessor :displayable_topics, :permission, :subcategory_ids, :notification_level
+  attr_accessor :displayable_topics, :permission, :subcategory_ids, :notification_level, :has_children
 
   def self.last_updated_at
     order('updated_at desc').limit(1).pluck(:updated_at).first.to_i

app/models/site.rb

@@ -30,7 +30,7 @@ class Site
   end
 
   def groups
-    @groups ||= Group.order(:name).map { |g| {:id => g.id, :name => g.name}}
+    @groups ||= Group.order(:name).map { |g| { id: g.id, name: g.name } }
   end
 
   def user_fields
@@ -41,7 +41,7 @@ class Site
     @categories ||= begin
       categories = Category
         .secured(@guardian)
-        .includes(:topic_only_relative_url)
+        .includes(:topic_only_relative_url, :subcategories)
         .order(:position)
 
       unless SiteSetting.allow_uncategorized_topics
@@ -62,10 +62,11 @@ class Site
       categories.each do |category|
         category.notification_level = category_user[category.id]
         category.permission = CategoryGroup.permission_types[:full] if allowed_topic_create.include?(category.id)
+        category.has_children = category.subcategories.present?
         by_id[category.id] = category
       end
 
-      categories.reject! {|c| c.parent_category_id && !by_id[c.parent_category_id]}
+      categories.reject! { |c| c.parent_category_id && !by_id[c.parent_category_id] }
       categories
     end
   end

app/serializers/basic_category_serializer.rb

@@ -17,7 +17,8 @@ class BasicCategorySerializer < ApplicationSerializer
              :logo_url,
              :background_url,
              :can_edit,
-             :topic_template
+             :topic_template,
+             :has_children
 
   def include_parent_category_id?
     parent_category_id