Make thread_type editable.

api/comment_threads.rb

@@ -52,7 +52,7 @@ end
 
 put "#{APIPREFIX}/threads/:thread_id" do |thread_id|
   filter_blocked_content params["body"]
-  thread.update_attributes(params.slice(*%w[title body closed commentable_id group_id]))
+  thread.update_attributes(params.slice(*%w[title body closed commentable_id group_id thread_type]))
 
   if thread.errors.any?
     error 400, thread.errors.full_messages.to_json

models/comment_thread.rb

@@ -53,7 +53,7 @@ class CommentThread < Content
   has_many :comments, dependent: :destroy#, autosave: true# Use destroy to envoke callback on the top-level comments TODO async
   has_many :activities, autosave: true
 
-  attr_accessible :title, :body, :course_id, :commentable_id, :anonymous, :anonymous_to_peers, :closed
+  attr_accessible :title, :body, :course_id, :commentable_id, :anonymous, :anonymous_to_peers, :closed, :thread_type
 
   validates_presence_of :thread_type
   validates_presence_of :title
@@ -64,6 +64,7 @@ class CommentThread < Content
 
   before_create :set_last_activity_at
   before_update :set_last_activity_at, :unless => lambda { closed_changed? }
+  after_update :clear_endorsements
 
   before_destroy :destroy_subscriptions
 
@@ -141,6 +142,18 @@ private
     self.last_activity_at = Time.now.utc unless last_activity_at_changed?
   end
 
+  def clear_endorsements
+    if self.thread_type_changed?
+      # We use 'set' instead of 'update_attributes' because the Comment model has a 'before_update' callback that sets
+      # the last activity time on the thread. Therefore the callbacks would be mutually recursive and we end up with a
+      # 'SystemStackError'. The 'set' method skips callbacks and therefore bypasses this issue.
+      self.comments.each do |comment|
+        comment.set :endorsed, false
+        comment.set :endorsement, nil
+      end
+    end
+  end
+
   def destroy_subscriptions
     subscriptions.delete_all
   end

spec/api/comment_thread_spec.rb

@@ -556,12 +556,20 @@ describe "app" do
       
       it "update information of comment thread" do
         thread = CommentThread.first
-        put "/api/v1/threads/#{thread.id}", body: "new body", title: "new title", commentable_id: "new_commentable_id"
+        comment = thread.comments.first
+        comment.endorsed = true
+        comment.endorsement = {:user_id => "42", :time => DateTime.now}
+        comment.save
+        put "/api/v1/threads/#{thread.id}", body: "new body", title: "new title", commentable_id: "new_commentable_id", thread_type: "question"
         last_response.should be_ok
         changed_thread = CommentThread.find(thread.id)
         changed_thread.body.should == "new body"
         changed_thread.title.should == "new title"
         changed_thread.commentable_id.should == "new_commentable_id"
+        changed_thread.thread_type.should == "question"
+        comment.reload
+        comment.endorsed.should == false
+        comment.endorsement.should == nil
         check_thread_result_json(nil, changed_thread, parse(last_response.body))
       end
       it "returns 400 when the thread does not exist" do