FEATURE: apply pinning to hot topic lists (#25690)

pinned topics should be pinned even on hot lists so it can be used as a
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app/models/topic_hot_score.rb

@@ -48,7 +48,9 @@ class TopicHotScore < ActiveRecord::Base
         AND topics.deleted_at IS NULL
         AND topics.archetype <> :private_message
         AND topics.created_at <= :now
-      ORDER BY topics.bumped_at desc
+      ORDER BY
+        CASE WHEN topics.pinned_at IS NOT NULL THEN 0 ELSE 1 END ASC,
+        topics.bumped_at desc
       LIMIT :max
     SQL
 

lib/topic_query.rb

@@ -339,7 +339,7 @@ class TopicQuery
   end
 
   def list_hot
-    create_list(:hot, unordered: true) do |topics|
+    create_list(:hot, unordered: true, prioritize_pinned: true) do |topics|
       topics = remove_muted_topics(topics, user)
       topics = remove_muted_categories(topics, user, exclude: options[:category])
       TopicQuery.remove_muted_tags(topics, user, options)
@@ -506,10 +506,12 @@ class TopicQuery
       DiscoursePluginRegistry.apply_modifier(:topic_query_create_list_topics, topics, options, self)
 
     options = options.merge(@options)
-    if %w[activity default].include?(options[:order] || "activity") && !options[:unordered] &&
+
-         filter != :private_messages
+    apply_pinning = filter != :private_messages
-      topics = prioritize_pinned_topics(topics, options)
+    apply_pinning &&= %w[activity default].include?(options[:order] || "activity")
-    end
+    apply_pinning &&= !options[:unordered] || options[:prioritize_pinned]
+
+    topics = prioritize_pinned_topics(topics, options) if apply_pinning
 
     topics = topics.to_a
 

spec/lib/topic_query_spec.rb

@@ -76,6 +76,25 @@ RSpec.describe TopicQuery do
   end
 
   describe "#list_hot" do
+    it "keeps pinned topics on top" do
+      pinned_topic =
+        Fabricate(
+          :topic,
+          created_at: 1.hour.ago,
+          pinned_at: 1.hour.ago,
+          pinned_globally: true,
+          like_count: 1,
+        )
+      _topic = Fabricate(:topic, created_at: 5.minute.ago, like_count: 100)
+      topic = Fabricate(:topic, created_at: 1.minute.ago, like_count: 100)
+
+      # pinned topic is older so generally it would not hit the batch without
+      # extra special logic
+      TopicHotScore.update_scores(2)
+
+      expect(TopicQuery.new(nil).list_hot.topics.map(&:id)).to eq([pinned_topic.id, topic.id])
+    end
+
     it "excludes muted categories and topics" do
       muted_category = Fabricate(:category)
       muted_topic = Fabricate(:topic, category: muted_category)