anonymous grading setting cannot be removed

anonymous grading cannot be disabled when editing an existing
anonymous assignment

closes EVAL-3449
flag=anonymous_marking

test plan:
- create an anonymous assignment
- edit the anonymous assignment and verify that the anonymous grading
  checkbox can be toggled off

Change-Id: Ie2028614a2e2f8e135e4cafc2be5c8a5e511ccb6
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/326551
QA-Review: Cameron Ray <cameron.ray@instructure.com>
Product-Review: Cameron Ray <cameron.ray@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Derek Williams <derek.williams@instructure.com>

spec/coffeescripts/views/assignments/EditViewSpec.jsx

@@ -1694,12 +1694,21 @@ QUnit.module('EditView: anonymous grading', hooks => {
 
   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})
+    const view = editView({id: '1', is_quiz_lti_assignment: true, anonymous_grading: true})
     view.$el.appendTo($('#fixtures'))
     view.afterRender()
     const anonymousGradingCheckbox = view.$el.find('input#assignment_anonymous_grading')
     strictEqual(anonymousGradingCheckbox.prop('disabled'), true)
   })
+
+  test('is enabled when creating a quiz lti assignment with anonymous grading turned on', () => {
+    ENV.ANONYMOUS_GRADING_ENABLED = true
+    const view = editView({id: null, is_quiz_lti_assignment: true, anonymous_grading: true})
+    view.$el.appendTo($('#fixtures'))
+    view.afterRender()
+    const anonymousGradingCheckbox = view.$el.find('input#assignment_anonymous_grading')
+    strictEqual(anonymousGradingCheckbox.prop('disabled'), false)
+  })
 })
 
 QUnit.module('EditView: Anonymous Instructor Annotations', hooks => {

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

@@ -1130,7 +1130,10 @@ 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(),
+    anonymousGradingCheckboxDisabled:
+      !this.assignment.isNew() &&
+      this.assignment.isQuizLTIAssignment() &&
+      this.assignment.anonymousGrading(),
   })
 }
 

ui/features/assignment_edit/jst/EditView.handlebars

@@ -206,7 +206,7 @@
                 class="GradeAnonymously__Checkbox"
                 id="assignment_anonymous_grading"
                 name="anonymous_grading"
-                disabled="{{anonymousGradingCheckboxDisabled}}"
+                disabled=anonymousGradingCheckboxDisabled
               }}
               {{#t}}Graders cannot view student names{{/t}}
               <div id="anonymous-lti-text" style="{{hiddenUnless isQuizLTIAssignment}};font-size: 0.9em">