add text to anonymous grading box

also disables the box if the assignment is a new quiz and already
anonymous

closes EVAL-3390
flag=anonymous_marking

test plan:
- create/edit a new quiz
- notice the new text under the anonymous grading checkbox
- edit a new quiz where anonymous grading is already enabled
- notice the checkbox is disabled and cannot be turned off

Change-Id: Ibc0e872c89ad6e932da55e93c93026e4dc492f11
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/324649
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Kai Bjorkman <kbjorkman@instructure.com>
QA-Review: Kai Bjorkman <kbjorkman@instructure.com>
Product-Review: Jody Sailor

spec/coffeescripts/views/assignments/EditViewSpec.jsx

@@ -1674,6 +1674,13 @@ QUnit.module('EditView: anonymous grading', hooks => {
     strictEqual(view.$el.find('input#assignment_anonymous_grading').length, 1)
   })
 
+  test('shows warning text under checkbox when assignment is Quiz LTI', () => {
+    ENV.ANONYMOUS_GRADING_ENABLED = true
+    const view = editView({is_quiz_lti_assignment: true})
+    strictEqual(view.toJSON().anonymousGradingEnabled, true)
+    strictEqual(view.$el.find('#anonymous-lti-text').length, 1)
+  })
+
   test('is disabled when group assignment is enabled', () => {
     ENV.ANONYMOUS_GRADING_ENABLED = true
     ENV.GROUP_CATEGORIES = [{id: '1', name: 'Group Category #1'}]
@@ -1684,6 +1691,15 @@ QUnit.module('EditView: anonymous grading', hooks => {
 
     strictEqual(anonymousGradingCheckbox.prop('disabled'), true)
   })
+
+  test('is disabled when editing a quiz lti assignment with anonymous grading turned on', () => {
+    ENV.ANONYMOUS_GRADING_ENABLED = true
+    const view = editView({is_quiz_lti_assignment: true, anonymous_grading: true})
+    view.$el.appendTo($('#fixtures'))
+    view.afterRender()
+    const anonymousGradingCheckbox = view.$el.find('input#assignment_anonymous_grading')
+    strictEqual(anonymousGradingCheckbox.prop('disabled'), true)
+  })
 })
 
 QUnit.module('EditView: Anonymous Instructor Annotations', hooks => {

ui/features/assignment_edit/backbone/views/EditView.jsx

@@ -1130,6 +1130,7 @@ EditView.prototype.toJSON = function () {
       (typeof ENV !== 'undefined' && ENV !== null
         ? ENV.ANONYMOUS_INSTRUCTOR_ANNOTATIONS_ENABLED
         : void 0) || false,
+    anonymousGradingCheckboxDisabled: !this.assignment.isNew() && this.assignment.isQuizLTIAssignment() && this.assignment.anonymousGrading(),
   })
 }
 

ui/features/assignment_edit/jst/EditView.handlebars

@@ -206,8 +206,12 @@
                 class="GradeAnonymously__Checkbox"
                 id="assignment_anonymous_grading"
                 name="anonymous_grading"
+                disabled="{{anonymousGradingCheckboxDisabled}}"
               }}
               {{#t}}Graders cannot view student names{{/t}}
+              <div id="anonymous-lti-text" style="{{hiddenUnless isQuizLTIAssignment}};font-size: 0.9em">
+                {{#t}}Once enabled for New Quizzes, anonymous grading will not be able to be toggled off.{{/t}}
+              </div>
             </label>
 
             <label class="checkbox" for="assignment_graders_anonymous_to_graders" style="{{hiddenUnless showGradersAnonymousToGradersCheckbox}}">