ensure conversations with deleted users load correctly

fixes regression from #7471

test plan:
1. start a conversation with another one or more users
2. delete one of the users
3. ensure the conversation still loads (you should see all participants
   and messages)

Change-Id: Ic0e567f22010864054f7396553b43173110be317
Reviewed-on: https://gerrit.instructure.com/9211

Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Cameron Matheson <cameron@instructure.com>

app/models/conversation_participant.rb

@@ -124,7 +124,7 @@ class ConversationParticipant < ActiveRecord::Base
     end
     return participants unless options[:include_context_info]
     # we do this to find out the contexts they share with the user
-    user.messageable_users(:ids => participants.map(&:id), :no_check_context => true).each { |user|
+    user.messageable_users(:ids => participants.map(&:id), :skip_visibility_checks => true).each { |user|
       context_info[user.id] = user
     }
     participants.each { |user|

app/models/user.rb

@@ -1999,7 +1999,8 @@ class User < ActiveRecord::Base
     # bother doing a query that's guaranteed to return no results.
     return [] if options[:ids] && options[:ids].empty?
 
-    user_conditions = [messageable_user_clause]
+    user_conditions = []
+    user_conditions << [messageable_user_clause] unless options[:skip_visibility_checks] && options[:ids]
     user_conditions << "users.id IN (#{options[:ids].map(&:to_i).join(', ')})" if options[:ids].present?
     user_conditions << "users.id NOT IN (#{options[:exclude_ids].map(&:to_i).join(', ')})" if options[:exclude_ids].present?
     if options[:search] && (parts = options[:search].strip.split(/\s+/)).present?
@@ -2072,7 +2073,7 @@ class User < ActiveRecord::Base
             AND conversation_participants.conversation_id = #{options[:conversation_id].to_i}
             #{user_condition_sql}
         SQL
-      elsif options[:no_check_context]
+      elsif options[:skip_visibility_checks] # we don't care about the contexts, we've passed in ids
         user_sql << <<-SQL
           SELECT #{MESSAGEABLE_USER_COLUMN_SQL}, NULL AS course_id, NULL AS group_id, NULL AS roles
           FROM users

spec/models/conversation_participant_spec.rb

@@ -153,6 +153,53 @@ describe ConversationParticipant do
     end
   end
 
+  context "participants" do
+    before do
+      @me = course_with_student(:active_all => true).user
+      @u1 = student_in_course(:active_all => true).user
+      @u2 = student_in_course(:active_all => true).user
+      @u3 = student_in_course(:active_all => true).user
+      @convo = @me.initiate_conversation([@u1.id, @u2.id, @u3.id])
+      @convo.add_message "ohai"
+      @u3.destroy
+      @u4 = student_in_course(:active_all => true).user
+
+      other_convo = @u4.initiate_conversation([@me.id])
+      message = other_convo.add_message "just between you and me"
+      @convo.add_message("haha i forwarded it", :forwarded_message_ids => [message.id])
+    end
+
+    it "should include shared contexts by default" do
+      users = @convo.reload.participants
+      users.each do |user|
+        user.common_groups.should == {}
+        if [@me.id, @u3.id].include? user.id
+          user.common_courses.should == {}
+        else
+          user.common_courses.should == {@course.id => ["StudentEnrollment"]}
+        end
+      end
+    end
+
+    it "should not include forwarded participants by default" do
+      users = @convo.reload.participants
+      users.map(&:id).sort.should eql [@me.id, @u1.id, @u2.id, @u3.id]
+    end
+
+    it "should not include shared contexts if asked not to" do
+      users = @convo.reload.participants(:include_context_info => false)
+      users.each do |user|
+        user.common_groups.should be_nil
+        user.common_courses.should be_nil
+      end
+    end
+
+    it "should include include forwarded participants if requested" do
+      users = @convo.reload.participants(:include_indirect_participants => true)
+      users.map(&:id).sort.should eql [@me.id, @u1.id, @u2.id, @u3.id, @u4.id]
+    end
+  end
+
   context "move_to_user" do
     before do
       @user1 = user_model

spec/models/user_spec.rb

@@ -708,6 +708,14 @@ describe User do
       set_up_course_with_users
       @student.messageable_users.map(&:id).should_not include(@deleted_user.id)
       @student.messageable_users(:search => @deleted_user.name).map(&:id).should be_empty
+      @student.messageable_users(:ids => [@deleted_user.id]).map(&:id).should be_empty
+      @student.messageable_users(:skip_visibility_checks => true).map(&:id).should_not include(@deleted_user.id)
+      @student.messageable_users(:skip_visibility_checks => true, :search => @deleted_user.name).map(&:id).should be_empty
+    end
+
+    it "should include deleted iff skip_visibility_checks=true && ids are given" do
+      set_up_course_with_users
+      @student.messageable_users(:skip_visibility_checks => true, :ids => [@deleted_user.id]).map(&:id).should == [@deleted_user.id]
     end
 
     it "should only include users from the specified section" do