Fix incorrect date for graded discussions with todo dates

A graded discussion can have a todo date if it was converted
from an ungraded discussion to a graded discussion. In that
case we should not show to todo date on the modules page.

fixes LX-1964
flag=none

test plan:
- create an ungraded discussion and check the 'add to student
  to do' box and add a date
- create a module and add the ungraded discussion to it
- expect to see the to do date on the module item
- go back to the discussion and change it from ungraded
  to graded
- check the modules page, expect to see no date on the
  discussion module item
- add a due date to the discussion and return to the module
  page
- expect to see the due date on the discussion module item

Change-Id: If32c99af3aa5c49137a2e99593b090d30360dd8c
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/355009
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Robin Kuss <rkuss@instructure.com>
QA-Review: Robin Kuss <rkuss@instructure.com>
Product-Review: Sarah Gerard <sarah.gerard@instructure.com>

spec/selenium/context_modules/context_modules_spec.rb

@@ -216,6 +216,16 @@ describe "context modules" do
       expect(f(".due_date_display").text).to eq date_string(todo_date, :no_words)
     end
 
+    it "does not show the todo date on an graded discussion in a module", priority: "2" do
+      due_at = 3.days.from_now
+      todo_date = 3.days.from_now
+      @assignment = @course.assignments.create!(name: "assignemnt", due_at:)
+      @discussion = @course.discussion_topics.create!(title: "Graded Discussion", assignment: @assignment, todo_date:)
+      @mod.add_item(type: "discussion_topic", id: @discussion.id)
+      go_to_modules
+      expect(f(".due_date_display").text).to eq date_string(due_at, :no_words)
+    end
+
     it "edits available/until dates on a ungraded discussion in a module", priority: "2" do
       available_from = 2.days.from_now
       available_until = 4.days.from_now

ui/shared/context-modules/jquery/index.jsx

@@ -302,7 +302,7 @@ window.modules = (function () {
               }
               if (ENV.IN_PACED_COURSE && !ENV.IS_STUDENT) {
                 $context_module_item.find('.due_date_display').remove()
-              } else if (info.todo_date != null) {
+              } else if (info.todo_date != null && info.points_possible == null) {
                 data.due_date_display = dateString(info.todo_date)
               } else if (info.due_date != null) {
                 if (info.past_due != null) {