correct random suggested topic selection

app/services/random_topic_selector.rb

@@ -4,7 +4,6 @@ class RandomTopicSelector
   BACKFILL_LOW_WATER_MARK = 500
 
   def self.backfill(category=nil)
-
     exclude = category.try(:topic_id)
 
     # don't leak private categories into the "everything" group
@@ -20,8 +19,11 @@ class RandomTopicSelector
     options[:category] = category.id if category
 
     query = TopicQuery.new(user, options)
+
+
     results = query.latest_results.order('RANDOM()')
                    .where(closed: false, archived: false)
+                   .where("topics.created_at > ?", SiteSetting.suggested_topics_max_days_old.days.ago)
                    .limit(BACKFILL_SIZE)
                    .reorder('RANDOM()')
                    .pluck(:id)

lib/suggested_topics_builder.rb

@@ -25,10 +25,6 @@ class SuggestedTopicsBuilder
     if @category_id && SiteSetting.limit_suggested_to_category?
       results = results.where(category_id: @category_id)
     end
-
-    # Suggested topics should not be more than n days old
-    results = results.where("topics.created_at > ?", SiteSetting.suggested_topics_max_days_old.days.ago)
-
     results = results.to_a.reject { |topic| @category_topic_ids.include?(topic.id) }
 
     unless results.empty?

spec/components/suggested_topics_builder_spec.rb

@@ -95,21 +95,6 @@ describe SuggestedTopicsBuilder do
       end
     end
 
-    context "adding topics that are more than n days old" do
-      let!(:new_topic) { Fabricate(:topic, created_at: 2.days.ago) }
-      let!(:old_topic) { Fabricate(:topic, created_at: 3.years.ago) }
-
-      it "adds topics based on suggested_topics_max_days_old setting" do
-        SiteSetting.suggested_topics_max_days_old = 365
-
-        builder.add_results(Topic)
-        expect(builder.size).to eq(1)
-        expect(builder).not_to be_full
-        expect(builder.excluded_topic_ids.include?(old_topic.id)).to eq(false)
-        expect(builder.excluded_topic_ids.include?(new_topic.id)).to eq(true)
-      end
-    end
-
     context "category definition topics" do
       let!(:category) { Fabricate(:category) }
 

spec/components/topic_query_spec.rb

@@ -620,6 +620,26 @@ describe TopicQuery do
         expect(suggested_topics).to be_blank
       end
 
+      context 'random suggested' do
+
+        let!(:new_topic) { Fabricate(:topic, created_at: 2.days.ago) }
+        let!(:old_topic) { Fabricate(:topic, created_at: 3.years.ago) }
+
+        it 'respects suggested_topics_max_days_old' do
+          SiteSetting.suggested_topics_max_days_old = 1365
+          tt = topic
+
+          RandomTopicSelector.clear_cache!
+          expect(topic_query.list_suggested_for(tt).topics.length).to eq(2)
+
+          SiteSetting.suggested_topics_max_days_old = 365
+          RandomTopicSelector.clear_cache!
+
+          expect(topic_query.list_suggested_for(tt).topics.length).to eq(1)
+        end
+
+      end
+
       context 'with some existing topics' do
         let!(:partially_read) { Fabricate(:post, user: creator).topic }
         let!(:new_topic) { Fabricate(:post, user: creator).topic }