Category descriptions should not appear in digests

app/models/topic.rb

@@ -5,6 +5,7 @@ require_dependency 'rate_limiter'
 require_dependency 'text_sentinel'
 require_dependency 'text_cleaner'
 require_dependency 'trashable'
+require_dependency 'archetype'
 
 class Topic < ActiveRecord::Base
   include ActionView::Helpers::SanitizeHelper
@@ -228,14 +229,21 @@ class Topic < ActiveRecord::Base
 
   # Returns hot topics since a date for display in email digest.
   def self.for_digest(user, since)
-    Topic
-      .visible
-      .secured(Guardian.new(user))
-      .where(closed: false, archived: false)
-      .created_since(since)
-      .listable_topics
-      .order(:percent_rank)
-      .limit(100)
+    topics = Topic
+              .visible
+              .secured(Guardian.new(user))
+              .where(closed: false, archived: false)
+              .created_since(since)
+              .listable_topics
+              .order(:percent_rank)
+              .limit(100)
+
+    category_topic_ids = Category.pluck(:topic_id).compact!
+    if category_topic_ids.present?
+      topics = topics.where("id NOT IN (?)", category_topic_ids)
+    end
+
+    topics
   end
 
   def update_meta_data(data)

spec/models/topic_spec.rb

@@ -1116,6 +1116,25 @@ describe Topic do
     end
   end
 
+  describe 'for_digest' do
+    let(:user) { Fabricate.build(:user) }
+
+    it "returns none when there are no topics" do
+      Topic.for_digest(user, 1.year.ago).should be_blank
+    end
+
+    it "doesn't return category topics" do
+      Fabricate(:category)
+      Topic.for_digest(user, 1.year.ago).should be_blank
+    end
+
+    it "returns regular topics" do
+      topic = Fabricate(:topic)
+      Topic.for_digest(user, 1.year.ago).should == [topic]
+    end
+
+  end
+
   describe 'secured' do
     it 'can remove secure groups' do
       category = Fabricate(:category, read_restricted: true)
@@ -1127,7 +1146,7 @@ describe Topic do
       # for_digest
 
       Topic.for_digest(Fabricate(:user), 1.year.ago).count.should == 0
-      Topic.for_digest(Fabricate(:admin), 1.year.ago).count.should == 2
+      Topic.for_digest(Fabricate(:admin), 1.year.ago).count.should == 1
     end
   end