WithError return Error and add ToError to return error

http/statuscode/error.go

@@ -67,11 +67,13 @@ func (e Error) Error() string {
 	return e.Err.Error()
 }
 
-// WithError returns a new error.
-func (e Error) WithError(err error) error {
+// WithError returns a new Error.
+//
+// If err is nil, Code of the returned error is equal to 200.
+func (e Error) WithError(err error) Error {
 	switch _err := err.(type) {
 	case nil:
-		return nil
+		return Error{Code: 200}
 
 	case Error:
 		return _err
@@ -93,6 +95,13 @@ func (e Error) WithMessage(msg string, args ...interface{}) Error {
 	return e
 }
 
+func (e Error) ToError(err error) error {
+	if err != nil {
+		err = e.WithError(err)
+	}
+	return err
+}
+
 // ServeHTTP implements the interface http.Handler.
 func (e Error) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	switch err := e.Err.(type) {

result/code/error.go

@@ -64,11 +64,13 @@ func (e Error[T]) WithCtx(ctx any) Error[T] {
 	return e
 }
 
-// WithError returns a new error, which inspects the error code and message from err.
-func (e Error[T]) WithError(err error) error {
+// WithError returns a new Error, which inspects the error code and message from err.
+//
+// If err is nil, return an empty Error ZERO.
+func (e Error[T]) WithError(err error) Error[T] {
 	switch _e := err.(type) {
 	case nil:
-		return nil
+		return Error[T]{}
 
 	case Error[T]:
 		return _e
@@ -96,6 +98,13 @@ func (e Error[T]) WithMessage(msgfmt string, msgargs ...interface{}) Error[T] {
 	return e
 }
 
+func (e Error[T]) ToError(err error) error {
+	if err != nil {
+		err = e.WithError(err)
+	}
+	return err
+}
+
 // Respond sends the error as result.Response by the responder.
 func (e Error[T]) Respond(responder any) {
 	result.Err(e).Respond(responder)

result/code/error_test.go

@@ -20,7 +20,7 @@ import (
 )
 
 func TestError(t *testing.T) {
-	e := NewError("Ok", "").WithError(errors.New("test")).(Error[string]).
+	e := NewError("Ok", "").WithError(errors.New("test")).
 		WithCtx(200).WithMessage("").WithMessage("%s", "msg")
 
 	expect := "Ok: msg"