Fix comments-dependent scopes

app/models/bubble.rb

@@ -11,11 +11,16 @@ class Bubble < ApplicationRecord
   scope :reverse_chronologically, -> { order created_at: :desc, id: :desc }
   scope :chronologically, -> { order created_at: :asc, id: :asc }
 
-  scope :ordered_by_activity, -> do
-    left_joins(:messages).merge(Message.comments).group(:id).order(Arel.sql("COUNT(messages.id) + boost_count DESC"))
+  scope :left_joins_comments, -> do
+    left_joins(:messages).merge(Message.left_joins_messageable(:comments))
   end
+
+  scope :ordered_by_activity, -> do
+    left_joins_comments.select("bubbles.*, COUNT(comments.id) + boost_count AS activity").group(:id).order("activity DESC")
+  end
+
   scope :ordered_by_comments, -> do
-    left_joins(:messages).merge(Message.comments).group(:id).order("COUNT(messages.id) DESC")
+    left_joins_comments.select("bubbles.*, COUNT(comments.id) AS comment_count").group(:id).order("comment_count DESC")
   end
 
   scope :with_status, ->(status) do

app/models/message.rb

@@ -4,4 +4,8 @@ class Message < ApplicationRecord
   delegated_type :messageable, types: Messageable::TYPES, inverse_of: :message, dependent: :destroy
 
   scope :chronologically, -> { order created_at: :asc, id: :desc }
+
+  scope :left_joins_messageable, ->(messageable_type) do
+    joins "LEFT OUTER JOIN #{messageable_type} ON messages.messageable_id = #{messageable_type}.id"
+  end
 end

test/models/bubble_test.rb

@@ -24,6 +24,15 @@ class BubbleTest < ActiveSupport::TestCase
     assert_includes Bubble.search("haggis"), bubble
   end
 
+  test "ordering by activity" do
+    bubbles(:layout).update! boost_count: 1_000
+    assert_equal bubbles(:layout, :logo, :shipping, :text), Bubble.ordered_by_activity.to_a
+  end
+
+  test "ordering by comments" do
+    assert_equal bubbles(:logo, :layout, :shipping, :text), Bubble.ordered_by_comments.to_a
+  end
+
   test "mentioning" do
     bubble = buckets(:writebook).bubbles.create! title: "Insufficient haggis", creator: users(:kevin)
     bubbles(:logo).capture Comment.new(body: "I hate haggis")