Resolve "Error 500 for /api/v4/projects/ID/services/jira"

app/models/project_services/data_fields.rb

@@ -50,7 +50,7 @@ module DataFields
     end
 
     def data_fields_present?
-      data_fields.persisted?
+      data_fields.present?
     rescue NotImplementedError
       false
     end

changelogs/unreleased/34770-error-500-for-api-v4-projects-id-services-jira-nomethoderror-undefi.yml

+---
+title: Fix project service API 500 error
+merge_request: 19367
+author:
+type: fixed

spec/models/project_services/data_fields_spec.rb

@@ -74,6 +74,12 @@ describe DataFields do
         expect(service.url_changed?).to be_falsy
       end
     end
+
+    describe 'data_fields_present?' do
+      it 'returns true from the issue tracker service' do
+        expect(service.data_fields_present?).to be true
+      end
+    end
   end
 
   context 'when data are stored in data_fields' do
@@ -92,6 +98,18 @@ describe DataFields do
     end
   end
 
+  context 'when service and data_fields are not persisted' do
+    let(:service) do
+      JiraService.new
+    end
+
+    describe 'data_fields_present?' do
+      it 'returns true' do
+        expect(service.data_fields_present?).to be true
+      end
+    end
+  end
+
   context 'when data are stored in properties' do
     let(:service) { create(:jira_service, :without_properties_callback, properties: properties) }
 

spec/requests/api/services_spec.rb

@@ -102,7 +102,7 @@ describe API::Services do
         expect(json_response['properties'].keys).to match_array(service_instance.api_field_names)
       end
 
-      it "returns empty hash if properties and data fields are empty" do
+      it "returns empty hash or nil values if properties and data fields are empty" do
         # deprecated services are not valid for update
         initialized_service.update_attribute(:properties, {})
 
@@ -114,7 +114,7 @@ describe API::Services do
         get api("/projects/#{project.id}/services/#{dashed_service}", user)
 
         expect(response).to have_gitlab_http_status(200)
-        expect(json_response['properties'].keys).to be_empty
+        expect(json_response['properties'].values.compact).to be_empty
       end
 
       it "returns error when authenticated but not a project owner" do