expose poll_choice#is_correct to students when available

fixes CNVS-13474
This commit exposes the is_correct attribute on poll_choices when a
student has submitted their answer to the latest poll_session, and that
poll_session has been closed.

Test plan
- As a teacher, create a poll, relevant poll choices, and a poll session
- Publish the poll session
- As a student, at this point is_correct should not be viewable on poll
  choices
- As a student, submit a poll submission
- As a student, at this point is_correct should not be viewable on poll
  choices
- As a teacher, close the poll session
- As a student, at this point is_correct should be viewable on poll
  choices

Change-Id: I20a8bb534affe5e1a23c1dddbb727043535dd23d
Reviewed-on: https://gerrit.instructure.com/36031
Reviewed-by: Jason Madsen <jmadsen@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Trevor deHaan <tdehaan@instructure.com>
Product-Review: Josh Simpson <jsimpson@instructure.com>

app/controllers/polling/poll_choices_controller.rb

@@ -85,7 +85,6 @@ module Polling
     #
     def show
       @poll_choice = @poll.poll_choices.find(params[:id])
-
       if authorized_action(@poll, @current_user, :read)
         render json: serialize_jsonapi(@poll_choice)
       end

app/controllers/polling/polls_controller.rb

@@ -70,7 +70,7 @@ module Polling
     #   }
     #
     def index
-      @polls = @current_user.polls
+      @polls = @current_user.polls.order('created_at DESC')
       @polls = Api.paginate(@polls, self, api_v1_polls_url)
 
       render json: serialize_jsonapi(@polls)

app/models/polling/poll.rb

@@ -45,6 +45,24 @@ module Polling
       can :read
     end
 
+    def closed_and_viewable_for?(user)
+      results = poll_sessions.with_each_shard do |scope|
+        scope
+        .joins(:poll_submissions)
+        .where(["polling_poll_submissions.user_id = ? AND is_published=? AND course_id IN (?) AND (course_section_id IS NULL OR course_section_id IN (?))",
+                user,
+                false,
+                user.enrollments.map(&:course_id).compact,
+                user.enrollments.map(&:course_section_id).compact]
+              )
+        .order('polling_poll_sessions.created_at DESC')
+        .limit(1)
+        .exists?
+      end
+
+       results.any?
+    end
+
     def total_results
       poll_sessions.reduce(Hash.new(0)) do |poll_results, session|
         poll_results = poll_results.merge(session.results) do |key, poll_result_value, session_result_value|

app/serializers/polling/poll_choice_serializer.rb

@@ -31,7 +31,9 @@ module Polling
     end
 
     def student_keys
-      [:id, :text]
+      keys = [:id, :text]
+      keys << :is_correct if poll.closed_and_viewable_for?(current_user)
+      keys
     end
   end
 end

spec/apis/v1/polling/poll_choices_api_spec.rb

@@ -114,14 +114,31 @@ describe Polling::PollChoicesController, type: :request do
         response.code.should == '200'
       end
 
-      it "doesn't display is_correct within poll choices" do
+      context "with opened sessions" do
-        Polling::PollSession.create!(course: @course, poll: @poll)
+        it "doesn't display is_correct within poll choices" do
+          Polling::PollSession.create!(course: @course, poll: @poll).publish!
 
-        json = get_show
+          json = get_show
-        poll_choice_json = json['poll_choices'].first
+          poll_choice_json = json['poll_choices'].first
 
-        poll_choice_json.should_not have_key('is_correct')
+          poll_choice_json.should_not have_key('is_correct')
+        end
       end
+
+      context "with closed, available sessions" do
+        it "displays is_correct within poll choices" do
+          session = Polling::PollSession.create!(course: @course, poll: @poll)
+          session.publish!
+          session.poll_submissions.create!(user: @student, poll: @poll, poll_choice: @poll_choice)
+          session.close!
+
+          json = get_show
+          poll_choice_json = json['poll_choices'].first
+
+          poll_choice_json.should have_key('is_correct')
+        end
+      end
+
     end
   end
 

spec/models/polling/poll_spec.rb

@@ -42,6 +42,44 @@ describe Polling::Poll do
     end
   end
 
+  describe "#closed_and_viewable_for?" do
+    it "returns false if the latest poll session available to the user is opened" do
+      student = student_in_course(active_user:true).user
+      poll = @teacher.polls.create!(question: 'A Test Poll')
+      session = poll.poll_sessions.create(course: @course)
+      session.publish!
+
+      poll.closed_and_viewable_for?(student).should be_false
+    end
+
+    context "the latest poll session available to the user is closed" do
+      before(:each) do
+        @student = student_in_course(active_user:true).user
+        @poll = @teacher.polls.create!(question: 'A Test Poll')
+        @choice = @poll.poll_choices.create!(text: 'Choice A', is_correct: true)
+        @session = @poll.poll_sessions.create(course: @course)
+      end
+
+      it "returns true if the user has submitted" do
+        @session.publish!
+        @session.poll_submissions.create!(
+          poll: @poll,
+          user: @student,
+          poll_choice: @choice
+        )
+        @session.close!
+
+        @poll.closed_and_viewable_for?(@student).should be_true
+      end
+
+      it "returns false if the user hasn't submitted" do
+        @session.publish!
+        @session.close!
+        @poll.closed_and_viewable_for?(@student).should be_false
+      end
+    end
+  end
+
   describe "#total_results" do
     def create_submission(session, choice)
       student = student_in_course(active_user:true).user