1 files changed, 44 insertions, 0 deletions
diff --git a/app/services/merge_requests/update_reviewers_service.rb b/app/services/merge_requests/update_reviewers_service.rb
new file mode 100644
index 00000000000..8e974d75676
--- /dev/null
+++ b/app/services/merge_requests/update_reviewers_service.rb
@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+module MergeRequests
+  class UpdateReviewersService < UpdateService
+    def execute(merge_request)
+      return merge_request unless current_user&.can?(:update_merge_request, merge_request)
+
+      old_reviewers = merge_request.reviewers.to_a
+      old_ids = old_reviewers.map(&:id)
+      new_ids = new_user_ids(merge_request, update_attrs[:reviewer_ids], :reviewers)
+
+      return merge_request if merge_request.errors.any?
+      return merge_request if new_ids.size != update_attrs[:reviewer_ids].size
+      return merge_request if old_ids.to_set == new_ids.to_set # no-change
+
+      merge_request.update!(update_attrs.merge(reviewer_ids: new_ids))
+      handle_reviewers_change(merge_request, old_reviewers)
+      resolve_todos_for(merge_request)
+      execute_reviewers_hooks(merge_request, old_reviewers)
+
+      merge_request
+    end
+
+    private
+
+    def reviewer_ids
+      filter_sentinel_values(params.fetch(:reviewer_ids)).first(1)
+    end
+
+    def update_attrs
+      @attrs ||= { updated_by: current_user, reviewer_ids: reviewer_ids }
+    end
+
+    def execute_reviewers_hooks(merge_request, old_reviewers)
+      execute_hooks(
+        merge_request,
+        'update',
+        old_associations: { reviewers: old_reviewers }
+      )
+    end
+  end
+end
+
+MergeRequests::UpdateReviewersService.prepend_mod