fix locked discussions before due date

fixes VICE-4515
flag=discussion_create

test plan:
- create an UNgraded discussion with an
"available until" field
- edit the discussion to be graded
- set a new available until date
- the discussion's available until date should
match the assignment's

Change-Id: Ie385f9ec2c71d02cfa1ccf9a4a4aeeed9231db0c
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/355570
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Product-Review: Tamás Balogh <tamas.balogh@instructure.com>
Reviewed-by: Daniel Matyas Vincze <daniel.vincze@instructure.com>
QA-Review: Theo Sorriaux <theo.sorriaux@instructure.com>

app/graphql/mutations/update_discussion_topic.rb

@@ -101,6 +101,7 @@ class Mutations::UpdateDiscussionTopic < Mutations::DiscussionBase
           # Instantiate and execute UpdateAssignment mutation
           assignment_mutation = Mutations::UpdateAssignment.new(object: nil, context:, field: nil)
           assignment_result = assignment_mutation.resolve(input: updated_assignment_args)
+          discussion_topic.lock_at = input[:assignment][:lock_at] if input[:assignment][:lock_at]
 
           if assignment_result[:errors]
             return { errors: assignment_result[:errors] }

spec/graphql/mutations/update_discussion_topic_spec.rb

@@ -156,6 +156,7 @@ RSpec.describe Mutations::UpdateDiscussionTopic do
     args << peer_reviews_str(assignment[:peerReviews]) if assignment[:peerReviews]
     args << assignment_overrides_str(assignment[:assignmentOverrides]) if assignment[:assignmentOverrides]
     args << "forCheckpoints: #{assignment[:forCheckpoints]}" if assignment[:forCheckpoints]
+    args << "lockAt: \"#{assignment[:lockAt]}\"" if assignment[:lockAt]
 
     "assignment: { #{args.join(", ")} }"
   end
@@ -619,6 +620,14 @@ RSpec.describe Mutations::UpdateDiscussionTopic do
 
       expect(result["errors"]).to be_nil
     end
+
+    it "syncs the discussion and assignment lock_at field when the assignment date changes" do
+      lock_at = 6.months.from_now.iso8601
+      expect(@topic.lock_at).to be_nil
+      result = run_mutation(id: @topic.id, assignment: { lockAt: lock_at.to_s })
+      expect(result["errors"]).to be_nil
+      expect(@topic.reload.lock_at).to eq lock_at.to_s
+    end
   end
 
   context "discussion checkpoints" do