Show 100% complete if 0 expected documents

Changelog: fixed
EE: true

ee/app/views/admin/application_settings/_elasticsearch_form.html.haml

@@ -240,7 +240,7 @@
                 - processed_documents = subtask.documents_count_target
                 %p= _('Expected documents: %{expected_documents}') % { expected_documents: expected_documents }
                 - if processed_documents && expected_documents
-                  - percentage = ((processed_documents / expected_documents.to_f) * 100).round(2)
+                  - percentage = expected_documents > 0 ? ((processed_documents / expected_documents.to_f) * 100).round(2) : 100
                   %p= _('Documents reindexed: %{processed_documents} (%{percentage}%%)') % { processed_documents: processed_documents, percentage: percentage }
                   .progress
                     .progress-bar{ "aria-valuemax" => "100", "aria-valuemin" => "0", "aria-valuenow" => percentage, :role => "progressbar", :style => "width: #{percentage}%" }

ee/spec/views/admin/application_settings/_elasticsearch_form.html.haml_spec.rb

@@ -177,6 +177,18 @@
         expect(rendered).not_to include("Documents reindexed:")
       end
     end
+
+    context 'when there are 0 documents expected' do
+      let_it_be(:task) { create(:elastic_reindexing_task, state: :reindexing) }
+      let_it_be(:subtask) { create(:elastic_reindexing_subtask, elastic_reindexing_task: task, documents_count_target: 0, documents_count: 0) }
+
+      it 'renders 100% completed progress' do
+        render
+
+        expect(rendered).to include('Expected documents: 0')
+        expect(rendered).to include('Documents reindexed: 0 (100%)')
+      end
+    end
   end
 
   context 'when there are elasticsearch indexed namespaces' do