don't show discussion stream items to students in an unpublished course

Test Plan:
 * Create a course and don't publish it
 * Add a student to that course
 * Create a discussion topic as the teacher
 * Make sure there is no item for the topic in the student's stream
   ( make sure the student as at least one other active enrollment though because stream items don't show at all if a user has no enrollments at all)

closes #6200 #5432

Change-Id: Ib993edf139d3c971197c7876a01e9f9592583704
Reviewed-on: https://gerrit.instructure.com/7221
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>

app/models/discussion_entry.rb

@@ -88,13 +88,13 @@ class DiscussionEntry < ActiveRecord::Base
       # If the topic has been going for more than two weeks and it suddenly
       # got "popular" again, move it back up in user streams
       if !self.discussion_topic.for_assignment? && self.created_at && self.created_at > self.discussion_topic.created_at + 2.weeks && recent_entries.select{|e| e.created_at && e.created_at > 24.hours.ago }.length > 10
-        self.discussion_topic.participants
+        self.discussion_topic.active_participants
       # If the topic has beeng going for more than two weeks, only show
       # people who have been participating in the topic
       elsif self.created_at > self.discussion_topic.created_at + 2.weeks
         recent_entries.map(&:user_id).uniq
       else
-        self.discussion_topic.participants
+        self.discussion_topic.active_participants
       end
     else
       []

app/models/discussion_topic.rb

@@ -240,13 +240,13 @@ class DiscussionTopic < ActiveRecord::Base
   
   on_create_send_to_streams do
     if should_send_to_stream
-      self.participants
+      self.active_participants
     end
   end
   
   on_update_send_to_streams do
     if should_send_to_stream && (@delayed_just_posted || @content_changed || changed_state(:active, :post_delayed))
-      self.participants
+      self.active_participants
     end
   end
   
@@ -419,7 +419,7 @@ class DiscussionTopic < ActiveRecord::Base
 
   set_broadcast_policy do |p|
     p.dispatch :new_discussion_topic
-    p.to { participants - [user] }
+    p.to { active_participants - [user] }
     p.whenever { |record|
       record.context.available? and
       ((record.just_created and not record.post_delayed?) || record.changed_state(:active, :post_delayed))
@@ -433,6 +433,14 @@ class DiscussionTopic < ActiveRecord::Base
     ([self.user] + context.participants).uniq.select{|u| u}
   end
   
+  def active_participants
+    if !self.context.available? && self.context.respond_to?(:participating_admins)
+      self.context.participating_admins
+    else
+      self.participants
+    end
+  end
+  
   def posters
     users = self.discussion_entries.find(:all, :include => [:user]).map(&:user)
     users << self.user

spec/models/discussion_topic_spec.rb

@@ -317,6 +317,23 @@ describe DiscussionTopic do
       @parent_topic.should_send_to_stream.should be_true
       @subtopic.should_send_to_stream.should be_false
     end
+    
+    it "should not send stream items to students if course isn't published'" do
+      course
+      course_with_teacher(:course => @course, :active_all => true)
+      student_in_course(:course => @course, :active_all => true)
+      
+      topic = @course.discussion_topics.create(:title => "secret topic", :user => @teacher)
+      
+      StreamItem.for_user(@student).count.should == 0
+      StreamItem.for_user(@teacher).count.should == 1
+
+      topic.discussion_entries.create!
+
+      StreamItem.for_user(@student).count.should == 0
+      StreamItem.for_user(@teacher).count.should == 1
+    end
+    
   end
   
   context "posting first to view" do