show quiz descriptions to observers

test plan:
* be an observer
* should be able to see quiz descriptions (if published)

closes #CNVS-31029

Change-Id: I5f77d379c9540698fc8ee4d3f6066c846aaacccc
Reviewed-on: https://gerrit.instructure.com/90985
Tested-by: Jenkins
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
QA-Review: Heath Hales <hhales@instructure.com>
Product-Review: James Williams  <jamesw@instructure.com>

app/controllers/quizzes/quizzes_controller.rb

@@ -176,7 +176,8 @@ class Quizzes::QuizzesController < ApplicationController
       if session[:quiz_id] == @quiz.id && !request.xhr?
         session.delete(:quiz_id)
       end
-      @locked_reason = @quiz.locked_for?(@current_user, :check_policies => true, :deep_check_if_needed => true)
+      is_observer = @context_enrollment && @context_enrollment.observer?
+      @locked_reason = @quiz.locked_for?(@current_user, :check_policies => true, :deep_check_if_needed => true, :is_observer => is_observer)
       @locked = @locked_reason && !can_preview?
 
       @context_module_tag = ContextModuleItem.find_tag_with_preferred([@quiz, @quiz.assignment], params[:module_item_id])

app/models/quizzes/quiz.rb

@@ -748,7 +748,7 @@ class Quizzes::Quiz < ActiveRecord::Base
         locked = assignment_lock
       elsif (module_lock = locked_by_module_item?(user, opts[:deep_check_if_needed]))
         locked = lock_info.merge({ context_module: module_lock.context_module.attributes })
-      elsif !context.try_rescue(:is_public) && !context.grants_right?(user, :participate_as_student)
+      elsif !context.try_rescue(:is_public) && !context.grants_right?(user, :participate_as_student) && !opts[:is_observer]
         locked = lock_info.merge({ missing_permission: :participate_as_student.to_s })
       end
 

spec/selenium/quizzes/quizzes_student_spec.rb

@@ -235,4 +235,21 @@ describe 'quizzes' do
     take_and_answer_quiz
     expect(f("#section-tabs .grades .nav-badge").text).to eq "1"
   end
+
+  it "should show quiz descriptions to observers" do
+    @context = @course
+    quiz = quiz_model
+    description = "some description"
+    quiz.description = description
+    quiz.save!
+
+    @student = @user
+    @observer = user
+    @course.enroll_user(@observer, 'ObserverEnrollment', :enrollment_state => 'active', :associated_user_id => @student.id)
+    user_session(@observer)
+
+    open_quiz_show_page
+    
+    expect(f(".description")).to include_text(description)
+  end
 end