Restrict anonymize_students to active enrollments

With post policies, ignore submissions belonging to concluded or
inactive enrollments when considering whether an anonymously graded
assignment should anonymize students, rather than simply checking the
assignment's muted attribute (which does not take students' enrollment
states into consideration).

fixes TALLY-151
flag=none

Test plan:
- Have a course with New Gradebook and Post Policies enabled
- Enroll at least three students (S1, S2, S3)
- Set up an anonymous assignment (A1)
- Conclude S2's enrollment in the course
- Deactivate S3's enrollment in the course
- In Gradebook:
  - Check that A1 appears as anonymous and grades are concealed
  - Post grades for A1
  - Reload the page
  - Check that grades for A1 are unconcealed after reload, and that
    "Hide grades" is now possible but posting grades isn't
- Repeat the above in SpeedGrader

Change-Id: I4ae69c088376fe6ba1acc5e8c04dc5abd1706c82
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/222155
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Spencer Olson <solson@instructure.com>
Reviewed-by: Jeremy Neander <jneander@instructure.com>
QA-Review: Robin Kuss <rkuss@instructure.com>
Product-Review: Jonathan Fenton <jfenton@instructure.com>

app/models/assignment.rb

@@ -57,7 +57,7 @@ class Assignment < ActiveRecord::Base
     anonymous_instructor_annotations
   ].freeze
 
-  attr_accessor :previous_id, :copying, :user_submitted, :grade_posting_in_progress
+  attr_accessor :previous_id, :copying, :user_submitted, :grade_posting_in_progress, :unposted_anonymous_submissions
   attr_reader :assignment_changed, :posting_params_for_notifications
   attr_writer :updating_user
 
@@ -1430,6 +1430,23 @@ class Assignment < ActiveRecord::Base
     ])
   end
 
+  def self.preload_unposted_anonymous_submissions(assignments)
+    assignment_ids_with_unposted_anonymous_submissions = Assignment.
+      where(id: assignments, anonymous_grading: true).
+      where(
+        "EXISTS (?)", Submission.active.unposted.joins(user: :enrollments).
+          where("submissions.user_id = users.id").
+          where("submissions.assignment_id = assignments.id").
+          where("enrollments.course_id = assignments.context_id").
+          where(Enrollment.active_student_conditions)
+      ).
+      pluck(:id).to_set
+
+    assignments.each do |assignment|
+      assignment.unposted_anonymous_submissions = assignment_ids_with_unposted_anonymous_submissions.include?(assignment.id)
+    end
+  end
+
   def touch_on_unlock_if_necessary
     if self.unlock_at && Time.zone.now < self.unlock_at && (Time.zone.now + 1.hour) > self.unlock_at
       Shackles.activate(:master) do
@@ -3166,15 +3183,28 @@ class Assignment < ActiveRecord::Base
     end
   end
 
+  # If you're going to be checking this for multiple assignments, you may want
+  # to call .preload_unposted_anonymous_submissions on the lot of them first
   def anonymize_students?
     return false unless anonymous_grading?
 
     # Only anonymize students for moderated assignments if grades have not been published.
-    # Only anonymize students for non-moderated assignments if the assignment is muted.
-    moderated_grading? ? !grades_published? : muted?
+    return !grades_published? if moderated_grading?
+
+    # If Post Policies isn't enabled, we can just check whether the assignment is muted.
+    return muted? unless course.post_policies_enabled?
+
+    # Otherwise, only anonymize students if there's at least one active student with
+    # an unposted submission.
+    unposted_anonymous_submissions?
   end
   alias anonymize_students anonymize_students?
 
+  def unposted_anonymous_submissions?
+    Assignment.preload_unposted_anonymous_submissions([self]) unless defined? @unposted_anonymous_submissions
+    @unposted_anonymous_submissions
+  end
+
   def can_view_student_names?(user)
     return false if anonymize_students?
 

lib/api/v1/assignment_group.rb

@@ -43,6 +43,7 @@ module Api::V1::AssignmentGroup
       # Preload assignments' post policies for Assignment#assignment_json.
       if assignments.present? && assignments.first.context.post_policies_enabled?
         ActiveRecord::Associations::Preloader.new.preload(assignments, :post_policy)
+        Assignment.preload_unposted_anonymous_submissions(assignments)
       end
 
       user_content_attachments = opts[:preloaded_user_content_attachments]

spec/models/assignment_spec.rb

@@ -872,7 +872,7 @@ describe Assignment do
 
   describe '#anonymize_students?' do
     before(:once) do
-      @assignment = @course.assignments.build
+      @assignment = @course.assignments.create!
     end
 
     it 'returns false when the assignment is not graded anonymously' do
@@ -881,27 +881,69 @@ describe Assignment do
 
     context 'when the assignment is anonymously graded' do
       before(:once) do
-        @assignment.anonymous_grading = true
+        @assignment.update!(anonymous_grading: true)
       end
 
-      it 'returns true when the assignment is muted' do
-        @assignment.muted = true
-        expect(@assignment).to be_anonymize_students
+      context "when the assignment is moderated" do
+        before(:each) do
+          @assignment.moderated_grading = true
+        end
+
+        it 'returns true when the assignment is moderated and grades are unpublished' do
+          expect(@assignment).to be_anonymize_students
+        end
+
+        it 'returns false when the assignment is moderated and grades are published' do
+          @assignment.grades_published_at = Time.zone.now
+          expect(@assignment).not_to be_anonymize_students
+        end
       end
 
-      it 'returns false when the assignment is unmuted' do
-        expect(@assignment).not_to be_anonymize_students
-      end
+      context "when the assignment is unmoderated" do
+        context "when Post Policies is not enabled" do
+          it 'returns true when the assignment is muted' do
+            @assignment.mute!
+            expect(@assignment).to be_anonymize_students
+          end
 
-      it 'returns true when the assignment is moderated and grades are unpublished' do
-        @assignment.moderated_grading = true
-        expect(@assignment).to be_anonymize_students
-      end
+          it 'returns false when the assignment is unmuted' do
+            @assignment.unmute!
+            expect(@assignment).not_to be_anonymize_students
+          end
+        end
 
-      it 'returns false when the assignment is moderated and grades are published' do
-        @assignment.moderated_grading = true
-        @assignment.grades_published_at = Time.zone.now
-        expect(@assignment).not_to be_anonymize_students
+        context "when Post Policies is enabled" do
+          let(:course) { @assignment.course }
+          let(:active_student) { User.create! }
+          let(:student2) { User.create! }
+          let(:student3) { User.create! }
+
+          before(:each) do
+            course.enable_feature!(:new_gradebook)
+            PostPolicy.enable_feature!
+
+            course.enroll_student(active_student, workflow_state: :active)
+            course.enroll_student(student2, workflow_state: :active)
+            course.enroll_student(student3, workflow_state: :active)
+          end
+
+          it "returns true when at least one active student has an unposted submission" do
+            expect(@assignment).to be_anonymize_students
+          end
+
+          it "returns false when all active submissions are posted" do
+            student2.enrollments.find_by(course: course).conclude
+            student3.enrollments.find_by(course: course).deactivate
+
+            @assignment.post_submissions
+            expect(@assignment).not_to be_anonymize_students
+          end
+
+          it "returns false when all submissions are posted" do
+            @assignment.post_submissions
+            expect(@assignment).not_to be_anonymize_students
+          end
+        end
       end
     end
   end