add scoping overrides by active enrollment

Add scoping overrides by active enrollment to prevent
unenrolled students with overrides from preventing
assignments from saving.

fixes CNVS-21655

test plan:
- Create an assignment
- Assign a due date to a particular student
- Remove that user from the course
- Edit that assignment.
- Assignments override should no longer show.
- Save the assignment should now work.

Change-Id: If08da7119172c7918b15238195e39e07ae75ea16
Reviewed-on: https://gerrit.instructure.com/71305
Tested-by: Jenkins
Reviewed-by: Davis McClellan <dmcclellan@instructure.com>
QA-Review: Michael Hargiss <mhargiss@instructure.com>
Product-Review: Jason Sparks <jsparks@instructure.com>

Author: Michael Nomitch

app/controllers/assignments_controller.rb

@@ -422,7 +422,7 @@ def edit
         }),
         :ASSIGNMENT_OVERRIDES =>
           (assignment_overrides_json(
-            @assignment.overrides_for(@current_user)
+            @assignment.overrides_for(@current_user, ensure_set_not_empty: true)
             )),
         :ASSIGNMENT_INDEX_URL => polymorphic_url([@context, :assignments]),
         :DIFFERENTIATED_ASSIGNMENTS_ENABLED => @context.feature_enabled?(:differentiated_assignments),

app/controllers/discussion_topics_controller.rb

@@ -402,7 +402,7 @@ def edit
       if @topic.assignment.present?
         hash[:ATTRIBUTES][:assignment][:assignment_overrides] =
           (assignment_overrides_json(
-            @topic.assignment.overrides_for(@current_user)
+            @topic.assignment.overrides_for(@current_user, ensure_set_not_empty: true)
             ))
         hash[:ATTRIBUTES][:assignment][:has_student_submissions] = @topic.assignment.has_student_submissions?
       end

app/controllers/quizzes/quizzes_controller.rb

@@ -279,7 +279,7 @@ def edit
 
       hash = {
         :ASSIGNMENT_ID => @assignment.present? ? @assignment.id : nil,
-        :ASSIGNMENT_OVERRIDES => assignment_overrides_json(@quiz.overrides_for(@current_user)),
+        :ASSIGNMENT_OVERRIDES => assignment_overrides_json(@quiz.overrides_for(@current_user, ensure_set_not_empty: true)),
         :DIFFERENTIATED_ASSIGNMENTS_ENABLED => @context.feature_enabled?(:differentiated_assignments),
         :QUIZ => quiz_json(@quiz, @context, @current_user, session),
         :SECTION_LIST => sections.map { |section|

app/models/assignment_override.rb

@@ -69,6 +69,12 @@ class AssignmentOverride < ActiveRecord::Base
   after_save :update_cached_due_dates
   after_save :touch_assignment, :if => :assignment
 
+  def set_not_empty?
+    overridable = assignment? ? assignment : quiz
+    ['CourseSection', 'Group'].include?(self.set_type) ||
+    set.any? && overridable.context.current_enrollments.where(user_id: set).exists?
+  end
+
   def update_cached_due_dates
     return unless assignment?
     if due_at_overridden_changed? ||

lib/dates_overridable.rb

@@ -27,8 +27,13 @@ def overridden_for(user)
   end
 
   # All overrides, not just dates
-  def overrides_for(user)
-    AssignmentOverrideApplicator.overrides_for_assignment_and_user(self, user)
+  def overrides_for(user, opts={})
+    overrides = AssignmentOverrideApplicator.overrides_for_assignment_and_user(self, user)
+    if opts[:ensure_set_not_empty] 
+      overrides.select(&:set_not_empty?) 
+    else
+      overrides
+    end
   end
 
   def overridden_for?(user)

spec/lib/dates_overridable_spec.rb

@@ -59,6 +59,45 @@
     end
   end
 
+  describe "assignment overrides_for" do
+    before do
+      student_in_course(:course => course)
+    end
+
+    context "with adhoc" do
+      before do
+        override.override_due_at(7.days.from_now)
+        override.set_type = "ADHOC"
+        override.save!
+
+      end
+
+      it "returns adhoc overrides when active students enrolled in adhoc set" do
+        override_student = override.assignment_override_students.build
+        override_student.user = @student
+        override_student.save!
+
+        expect(overridable.overrides_for(@student, ensure_set_not_empty: true).size).to eq 1
+      end
+
+      it "returns nothing when no active students enrolled in adhoc set" do
+        expect(overridable.overrides_for(@student, ensure_set_not_empty: true)).to be_empty
+      end
+
+      it "returns nothing when active students enrolled in adhoc set removed" do
+        override_student = override.assignment_override_students.build
+        override_student.user = @student
+        override_student.save!
+
+        expect(overridable.overrides_for(@student, ensure_set_not_empty: true).size).to eq 1
+
+        override_student.user.enrollments.delete_all
+
+        expect(overridable.overrides_for(@student, ensure_set_not_empty: true)).to be_empty
+      end
+    end
+  end
+
   describe "has_overrides?" do
     subject { overridable.has_overrides? }
 

spec/models/assignment_override_spec.rb

@@ -662,4 +662,38 @@ def fancy_midnight(opts={})
       expect(@override.applies_to_students).to eq [@student]
     end
   end
+
+  describe "assignment_edits" do
+    before do
+      @override = assignment_override_model
+    end
+
+    it "returns false if no students who are active in course for ADHOC" do
+      @override.stubs(:set_type).returns "ADHOC"
+      @override.stubs(:set).returns []
+
+      expect(@override.set_not_empty?).to eq false
+    end
+
+    it "returns true if no students who are active in course and CourseSection or Group" do
+      @override.stubs(:set_type).returns "CourseSection"
+      @override.stubs(:set).returns []
+
+      expect(@override.set_not_empty?).to eq true
+
+      @override.stubs(:set_type).returns "Group"
+
+      expect(@override.set_not_empty?).to eq true
+    end
+
+    it "returns true if has students who are active in course for ADHOC" do
+      student = student_in_course(course: @override.assignment.context)
+      @override.set_type = "ADHOC"
+      @override_student = @override.assignment_override_students.build
+      @override_student.user = student.user
+      @override_student.save!
+
+      expect(@override.set_not_empty?).to eq true
+    end
+  end
 end