FIX: invalid cache for parent category with limit_suggested_to_category

app/services/random_topic_selector.rb

@@ -6,9 +6,6 @@ class RandomTopicSelector
   def self.backfill(category = nil)
     exclude = category&.topic_id
 
-    # don't leak private categories into the "everything" group
-    user = category ? CategoryFeaturedTopic.fake_admin : nil
-
     options = {
       per_page: category ? category.num_featured_topics : 3,
       visible: true,
@@ -16,9 +13,20 @@ class RandomTopicSelector
     }
 
     options[:except_topic_ids] = [category.topic_id] if exclude
-    options[:category] = category.id if category
 
-    query = TopicQuery.new(user, options)
+    if category
+      options[:category] = category.id
+      # NOTE: at the moment this site setting scopes tightly to a category (excluding subcats)
+      # this is done so we don't populate a junk cache
+      if SiteSetting.limit_suggested_to_category
+        options[:no_subcategories] = true
+      end
+
+      # don't leak private categories into the "everything" group
+      options[:guardian] = Guardian.new(CategoryFeaturedTopic.fake_admin)
+    end
+
+    query = TopicQuery.new(nil, options)
 
     results = query.latest_results.order('RANDOM()')
       .where(closed: false, archived: false)

lib/topic_query.rb

@@ -43,6 +43,7 @@ class TopicQuery
          page
          per_page
          visible
+         guardian
          no_definitions)
   end
 
@@ -90,7 +91,7 @@ class TopicQuery
     options.assert_valid_keys(TopicQuery.valid_options)
     @options = options.dup
     @user = user
-    @guardian = Guardian.new(@user)
+    @guardian = options[:guardian] || Guardian.new(@user)
   end
 
   def joined_topic_user(list = nil)