Force summary mode when user enters at the top of megalodoon topics.

app/assets/javascripts/discourse/lib/transform-post.js.es6

@@ -177,9 +177,9 @@ export default function transformPost(
 
     const postStream = topic.get("postStream");
     postAtts.userFilters = postStream.userFilters;
-    postAtts.topicSummaryEnabled = postStream.summary;
+    postAtts.topicSummaryEnabled = postStream.summary || topic.force_summary_mode;
     postAtts.topicWordCount = topic.word_count;
-    postAtts.hasTopicSummary = topic.has_summary;
+    postAtts.hasTopicSummary = topic.has_summary || topic.force_summary_mode;
   }
 
   if (postAtts.isDeleted) {

app/serializers/topic_view_serializer.rb

@@ -68,6 +68,7 @@ class TopicViewSerializer < ApplicationSerializer
              :participant_count,
              :destination_category_id,
              :pm_with_non_human_user,
+             :force_summary_mode,
 
   # TODO: Split off into proper object / serializer
   def details
@@ -299,6 +300,10 @@ class TopicViewSerializer < ApplicationSerializer
       object.topic.shared_draft.present?
   end
 
+  def force_summary_mode
+    object.force_summary_mode?
+  end
+
   private
 
   def private_message?(topic)

lib/topic_view.rb

@@ -405,6 +405,11 @@ class TopicView
       end
   end
 
+  def force_summary_mode?
+    @force_summary_mode ||=
+      (@topic.closed? && @topic.posts_count >= (MEGA_TOPIC_POSTS_COUNT * 2))
+  end
+
   protected
 
   def read_posts_set
@@ -482,7 +487,7 @@ class TopicView
     @filtered_posts = unfiltered_posts
 
     # Filters
-    if @filter == 'summary' || force_summary_mode?
+    if @filter == 'summary' || ((@post_number.blank? || @post_number.to_i == 1) && force_summary_mode?)
       @filtered_posts = @filtered_posts.summary(@topic.id)
       @contains_gaps = true unless force_summary_mode?
     end
@@ -572,9 +577,4 @@ class TopicView
   def is_mega_topic?
     @topic.posts_count >= MEGA_TOPIC_POSTS_COUNT
   end
-
-  def force_summary_mode?
-    @force_summary_mode ||=
-      (@topic.closed? && @topic.posts_count >= (MEGA_TOPIC_POSTS_COUNT * 2))
-  end
 end

spec/components/topic_view_spec.rb

@@ -365,22 +365,31 @@ describe TopicView do
     end
 
     describe 'when a megalodon topic is closed' do
+      before do
+        @original_const = TopicView::MEGA_TOPIC_POSTS_COUNT
+        TopicView.send(:remove_const, "MEGA_TOPIC_POSTS_COUNT")
+        TopicView.const_set("MEGA_TOPIC_POSTS_COUNT", 1)
+        topic.update!(closed: true)
+        SiteSetting.summary_max_results = 2
+      end
+
+      after do
+        TopicView.send(:remove_const, "MEGA_TOPIC_POSTS_COUNT")
+        TopicView.const_set("MEGA_TOPIC_POSTS_COUNT", @original_const)
+      end
+
       it 'should be forced into summary mode without gaps' do
-        begin
-          original_const = TopicView::MEGA_TOPIC_POSTS_COUNT
-          TopicView.send(:remove_const, "MEGA_TOPIC_POSTS_COUNT")
-          TopicView.const_set("MEGA_TOPIC_POSTS_COUNT", 1)
-          SiteSetting.summary_max_results = 2
-          topic.update!(closed: true)
+        topic_view = TopicView.new(topic.id, evil_trout, post_number: 1)
 
-          topic_view = TopicView.new(topic.id, evil_trout)
+        expect(topic_view.contains_gaps?).to eq(false)
+        expect(topic_view.posts).to eq([p5])
+      end
 
-          expect(topic_view.contains_gaps?).to eq(false)
-          expect(topic_view.posts).to eq([p5])
-        ensure
-          TopicView.send(:remove_const, "MEGA_TOPIC_POSTS_COUNT")
-          TopicView.const_set("MEGA_TOPIC_POSTS_COUNT", original_const)
-        end
+      it 'should not be forced into summary mode if post_number is not blank' do
+        topic_view = TopicView.new(topic.id, evil_trout, post_number: 2)
+
+        expect(topic_view.contains_gaps?).to eq(false)
+        expect(topic_view.posts).to eq([p1, p2, p3])
       end
     end