add duedatecacher run when adhoc overrides changed via api

This patchset adds a call to DueDateCacher.recompute to
Assignment#run_if_overrides_changed! to avoid situations where either
cleanup callbacks are skipped or other due date changes that would
change the cached due date.

fixes GRADE-677

test plan:
 - Create a course with at least 2 users
 - Create an assignment and assign it to just 2 of the users
 - Visit the gradebook and note both students are able to be graded
 - Return to the assignment settings and remove one of those users
   from the override
 - Visit the gradebook and note only the still assigned student is
   able to be graded

Change-Id: I3cedd13ecedcc1cb785e2a70589fd79bef48802d
Reviewed-on: https://gerrit.instructure.com/134028
Tested-by: Jenkins
Reviewed-by: Shahbaz Javeed <sjaveed@instructure.com>
Reviewed-by: Spencer Olson <solson@instructure.com>
QA-Review: Indira Pai <ipai@instructure.com>
Product-Review: Keith T. Garner <kgarner@instructure.com>

app/models/assignment.rb

@@ -2551,7 +2551,9 @@ class Assignment < ActiveRecord::Base
   def run_if_overrides_changed!(student_ids=nil)
     relocked_modules = []
     self.relock_modules!(relocked_modules, student_ids)
-    each_submission_type { |submission| submission.relock_modules!(relocked_modules, student_ids) if submission }
+    each_submission_type { |submission| submission&.relock_modules!(relocked_modules, student_ids)}
+
+    DueDateCacher.recompute(self)
 
     if only_visible_to_overrides?
       Rails.logger.info "GRADES: recalculating because assignment overrides on #{global_id} changed."

lib/api/v1/assignment_override.rb

@@ -301,6 +301,7 @@ module Api::V1::AssignmentOverride
         override.changed_student_ids.merge(defunct_student_ids)
         override.assignment_override_students.
           where(:user_id => defunct_student_ids.to_a).
+          in_batches.
           delete_all
       end
     end

spec/apis/v1/assignment_overrides_spec.rb

@@ -805,6 +805,20 @@ describe AssignmentOverridesController, type: :request do
 
       end
 
+      it "runs DueDateCacher after changing overrides" do
+        always_override_student = @student
+        remove_override_student = student_in_course(:course => @course).user
+        @override.assignment_override_students.create!(user: remove_override_student)
+        @override.reload
+
+        expect(DueDateCacher).to receive(:recompute).with(@assignment)
+        api_update_override(@course, @assignment, @override,
+          :assignment_override => { :student_ids => [always_override_student.id] })
+
+        @override.reload
+        expect(@override.assignment_override_students.map(&:user_id)).to eq([always_override_student.id])
+      end
+
       it "should allow changing the title" do
         @new_title = "new #{@title}"
         api_update_override(@course, @assignment, @override, :assignment_override => { :title => @new_title })