Remember assignee when moving an issue

app/services/issues/move_service.rb

@@ -48,7 +48,8 @@ module Issues
       new_params = { id: nil, iid: nil, label_ids: cloneable_label_ids,
                      milestone_id: cloneable_milestone_id,
                      project: @new_project, author: @old_issue.author,
-                     description: rewrite_content(@old_issue.description) }
+                     description: rewrite_content(@old_issue.description),
+                     assignee_ids: @old_issue.assignee_ids }
 
       new_params = @old_issue.serializable_hash.symbolize_keys.merge(new_params)
       CreateService.new(@new_project, @current_user, new_params).execute

changelogs/unreleased/41949-move.yml

+---
+title: Remember assignee when moving an issue
+merge_request:
+author:
+type: fixed

spec/services/issues/move_service_spec.rb

@@ -232,6 +232,28 @@ describe Issues::MoveService do
           end
         end
 
+        context 'issue with assignee' do
+          let(:assignee) { create(:user) }
+
+          before do
+            old_issue.assignees = [assignee]
+          end
+
+          it 'preserves assignee with access to the new issue' do
+            new_project.add_reporter(assignee)
+
+            new_issue = move_service.execute(old_issue, new_project)
+
+            expect(new_issue.assignees).to eq([assignee])
+          end
+
+          it 'ignores assignee without access to the new issue' do
+            new_issue = move_service.execute(old_issue, new_project)
+
+            expect(new_issue.assignees).to be_empty
+          end
+        end
+
         context 'notes with references' do
           before do
             create(:merge_request, source_project: old_project)