FIX: Category description topics shouldn't auto-close

app/models/category.rb

@@ -151,6 +151,7 @@ SQL
   def create_category_definition
     t = Topic.new(title: I18n.t("category.topic_prefix", category: name), user: user, pinned_at: Time.now, category_id: id)
     t.skip_callbacks = true
+    t.auto_close_days = nil
     t.save!
     update_column(:topic_id, t.id)
     t.posts.create(raw: post_template, user: user)

app/models/topic.rb

@@ -605,7 +605,7 @@ class Topic < ActiveRecord::Base
   # TODO: change this method, along with category's auto_close_days. Use hours.
   def auto_close_days=(num_days)
     @ignore_category_auto_close = true
-    set_auto_close(num_days * 24)
+    set_auto_close( num_days ? num_days * 24 : nil)
   end
 
   def self.auto_close

spec/models/category_spec.rb

@@ -210,6 +210,11 @@ describe Category do
       @category.topic_url.should be_present
     end
 
+    it "should not set its description topic to auto-close" do
+      category = Fabricate(:category, name: 'Closing Topics', auto_close_days: 1)
+      category.topic.auto_close_at.should be_nil
+    end
+
     describe "creating a new category with the same slug" do
       it "should have a blank slug" do
         Fabricate(:category, name: "Amazing Categóry").slug.should be_blank

spec/models/topic_spec.rb

@@ -1067,6 +1067,22 @@ describe Topic do
     end
   end
 
+  describe "auto_close_days=" do
+    subject(:topic) { Fabricate.build(:topic) }
+
+    it 'can take a number' do
+      Timecop.freeze(Time.zone.now) do
+        topic.auto_close_days = 2
+        topic.auto_close_at.should be_within_one_second_of(2.days.from_now)
+      end
+    end
+
+    it 'can take nil' do
+      topic.auto_close_days = nil
+      topic.auto_close_at.should be_nil
+    end
+  end
+
   describe 'set_auto_close' do
     let(:topic)         { Fabricate.build(:topic) }
     let(:closing_topic) { Fabricate.build(:topic, auto_close_days: 5) }