Fix transfering groups to root for EE

changelogs/unreleased/fix-group-transfer.yml

+---
+title: Fix transferring groups to root when EE features are enabled
+merge_request: 21915
+author:
+type: fixed

ee/app/services/ee/groups/transfer_service.rb

@@ -17,7 +17,7 @@ module EE
         return unless group.packages_feature_available?
 
         npm_packages = Packages::GroupPackagesFinder.new(current_user, group, package_type: :npm).execute
-        if !new_parent_group_has_same_root_ancestor? && npm_packages.exists?
+        if different_root_ancestor? && npm_packages.exists?
           raise_ee_transfer_error(:group_contains_npm_packages)
         end
       end
@@ -44,8 +44,8 @@ module EE
         raise ::Groups::TransferService::TransferError, EE_ERROR_MESSAGES[message]
       end
 
-      def new_parent_group_has_same_root_ancestor?
-        group.root_ancestor == new_parent_group.root_ancestor
+      def different_root_ancestor?
+        group.root_ancestor != new_parent_group&.root_ancestor
       end
     end
   end

ee/spec/services/groups/transfer_service_spec.rb

@@ -12,7 +12,7 @@ describe Groups::TransferService, '#execute' do
   before do
     stub_licensed_features(packages: true)
     group.add_owner(user)
-    new_group.add_owner(user)
+    new_group&.add_owner(user)
   end
 
   context 'with an npm package' do
@@ -50,6 +50,25 @@ describe Groups::TransferService, '#execute' do
           expect(group.parent).to eq(new_group)
         end
       end
+
+      context 'when transferring a group into a root group' do
+        let(:new_group) { nil }
+
+        it_behaves_like 'transfer not allowed'
+      end
+    end
+  end
+
+  context 'without an npm package' do
+    context 'when transferring a group into a root group' do
+      let(:group) { create(:group, parent: create(:group)) }
+
+      it 'allows transfer' do
+        transfer_service.execute(nil)
+
+        expect(transfer_service.error).not_to be
+        expect(group.parent).to be_nil
+      end
     end
   end