Preload ancestors for subgroups matching filter

Otherwise we'd only preload the ancestors that would fit the
page. That way, when a search result was on the first page, but the
ancestor didn't fit the page anymore. We would not have the preloaded
ancestor when rendering the hierarchy.

2 files changed, 36 insertions, 1 deletions

diff --git a/spec/controllers/groups/children_controller_spec.rb b/spec/controllers/groups/children_controller_spec.rb
index cb1b460fc0e..22d3076c269 100644
--- a/spec/controllers/groups/children_controller_spec.rb
+++ b/spec/controllers/groups/children_controller_spec.rb
@@ -160,6 +160,30 @@ describe Groups::ChildrenController do
           expect(json_response).to eq([])
         end
 
+        it 'succeeds if multiple pages contain matching subgroups' do
+          create(:group, parent: group, name: 'subgroup-filter-1')
+          create(:group, parent: group, name: 'subgroup-filter-2')
+
+          # Creating the group-to-nest first so it would be loaded into the
+          # relation first before it's parents, this is what would cause the
+          # crash in: https://gitlab.com/gitlab-org/gitlab-ce/issues/40785.
+          #
+          # If we create the parent groups first, those would be loaded into the
+          # collection first, and the pagination would cut off the actual search
+          # result. In this case the hierarchy can be rendered without crashing,
+          # it's just incomplete.
+          group_to_nest = create(:group, parent: group, name: 'subsubgroup-filter-3')
+          subgroup = create(:group, parent: group)
+          3.times do |i|
+            subgroup = create(:group, parent: subgroup)
+          end
+          group_to_nest.update!(parent: subgroup)
+
+          get :index, group_id: group.to_param, filter: 'filter', per_page: 3, format: :json
+
+          expect(response).to have_gitlab_http_status(200)
+        end
+
         it 'includes pagination headers' do
           2.times { |i| create(:group, :public, parent: public_subgroup, name: "filterme#{i}") }
 
diff --git a/spec/finders/group_descendants_finder_spec.rb b/spec/finders/group_descendants_finder_spec.rb
index 9cadd9a6000..375bcc9087e 100644
--- a/spec/finders/group_descendants_finder_spec.rb
+++ b/spec/finders/group_descendants_finder_spec.rb
@@ -73,7 +73,7 @@ describe GroupDescendantsFinder do
     end
 
     context 'with a filter' do
-      let(:params) { { filter: 'tes' } }
+      let(:params) { { filter: 'test' } }
 
       it 'includes only projects matching the filter' do
         _other_project = create(:project, namespace: group)
@@ -198,6 +198,17 @@ describe GroupDescendantsFinder do
             expect(finder.execute).to contain_exactly(subgroup, matching_project)
           end
 
+          context 'with a small page size' do
+            let(:params) { { filter: 'test', per_page: 1 } }
+
+            it 'contains all the ancestors of a matching subgroup regardless the page size' do
+              subgroup = create(:group, :private, parent: group)
+              matching = create(:group, :private, name: 'testgroup', parent: subgroup)
+
+              expect(finder.execute).to contain_exactly(subgroup, matching)
+            end
+          end
+
           it 'does not include the parent itself' do
             group.update!(name: 'test')