fixes #2731: Expunged posts should clear favorite groups

app/models/favorite_group.rb

@@ -18,6 +18,11 @@ class FavoriteGroup < ActiveRecord::Base
       where("favorite_groups.creator_id = ?", user_id)
     end
 
+    def for_post(post_id)
+      regexp = "(^#{post_id}$|^#{post_id} | #{post_id}$| #{post_id} )"
+      where("favorite_groups.post_ids ~ ?", regexp)
+    end
+
     def named(name)
       where("lower(name) = ?", name.to_s.mb_chars.downcase.strip)
     end

app/models/post.rb

@@ -959,6 +959,12 @@ class Post < ActiveRecord::Base
         groups.uniq
       end
     end
+
+    def remove_from_fav_groups
+      FavoriteGroup.for_post(id).find_each do |group|
+        group.remove!(self)
+      end
+    end
   end
 
   module UploaderMethods
@@ -1313,6 +1319,7 @@ class Post < ActiveRecord::Base
         update_children_on_destroy
         decrement_tag_post_counts
         remove_from_all_pools
+        remove_from_fav_groups
         destroy
         update_parent_on_destroy
       end