Merge pull request #2801 from thaJeztah/18.09_backport_change_error_m…

…essage

[18.09 backport] Include old error-message for backward compatibility

manager/controlapi/service.go

@@ -682,7 +682,10 @@ func (s *Server) CreateService(ctx context.Context, request *api.CreateServiceRe
 	})
 	switch err {
 	case store.ErrNameConflict:
-		return nil, status.Errorf(codes.AlreadyExists, "service %s already exists", request.Spec.Annotations.Name)
+		// Enhance the name-confict error to include the service name. The original
+		// `ErrNameConflict` error-message is included for backward-compatibility
+		// with older consumers of the API performing string-matching.
+		return nil, status.Errorf(codes.AlreadyExists, "%s: service %s already exists", err.Error(), request.Spec.Annotations.Name)
 	case nil:
 		return &api.CreateServiceResponse{Service: service}, nil
 	default:

manager/controlapi/service_test.go

@@ -623,6 +623,10 @@ func TestCreateService(t *testing.T) {
 	r, err = ts.Client.CreateService(context.Background(), &api.CreateServiceRequest{Spec: spec})
 	assert.Error(t, err)
 	assert.Equal(t, codes.AlreadyExists, testutils.ErrorCode(err))
+
+	// Make sure the error contains "name conflicts with an existing object" for
+	// backward-compatibility with older clients doing string-matching...
+	assert.Contains(t, err.Error(), "name conflicts with an existing object")
 }
 
 func TestSecretValidation(t *testing.T) {