feat: add ErrorWithDetail

errors.go

@@ -14,6 +14,11 @@ type ErrorWithStatus interface {
 	StatusCode() int
 }
 
+type ErrorWithDetail interface {
+	error
+	DetailMsg() string
+}
+
 // HTTPError is the error response used by the serialization part of the framework.
 type HTTPError struct {
 	Err      error       `json:"-" xml:"-"`                                                                                                                   // Developer readable error message. Not shown to the user to avoid security leaks.
@@ -40,7 +45,7 @@ func (e HTTPError) Error() string {
 			title = "HTTP Error"
 		}
 	}
-	return fmt.Sprintf("%d %s: %s", code, title, e.Detail)
+	return fmt.Sprintf("%d %s: %s", code, title, e.DetailMsg())
 }
 
 func (e HTTPError) StatusCode() int {
@@ -50,6 +55,10 @@ func (e HTTPError) StatusCode() int {
 	return e.Status
 }
 
+func (e HTTPError) DetailMsg() string {
+	return e.Detail
+}
+
 func (e HTTPError) Unwrap() error { return e.Err }
 
 // BadRequestError is an error used to return a 400 status code.
@@ -123,7 +132,7 @@ func (e NotAcceptableError) Unwrap() error { return HTTPError(e) }
 
 // ErrorHandler is the default error handler used by the framework.
 // It transforms any error into the unified error type [HTTPError],
-// Using the [ErrorWithStatus] interface.
+// Using the [ErrorWithStatus] and [ErrorWithDetail] interface.
 func ErrorHandler(err error) error {
 	errResponse := HTTPError{
 		Err: err,
@@ -141,11 +150,17 @@ func ErrorHandler(err error) error {
 		errResponse.Status = errorStatus.StatusCode()
 	}
 
+	// Check for detail
+	var errorDetail ErrorWithDetail
+	if errors.As(err, &errorDetail) {
+		errResponse.Detail = errorDetail.DetailMsg()
+	}
+
 	if errResponse.Title == "" {
 		errResponse.Title = http.StatusText(errResponse.Status)
 	}
 
-	slog.Error("Error "+errResponse.Title, "status", errResponse.StatusCode(), "detail", errResponse.Detail, "error", errResponse.Err)
+	slog.Error("Error "+errResponse.Title, "status", errResponse.StatusCode(), "detail", errResponse.DetailMsg(), "error", errResponse.Err)
 
 	return errResponse
 }

errors_test.go

@@ -10,12 +10,17 @@ import (
 
 type myError struct {
 	status int
+	err    HTTPError
+	detail string
 }
 
 var _ ErrorWithStatus = myError{}
+var _ ErrorWithDetail = myError{}
 
-func (e myError) Error() string   { return "test error" }
-func (e myError) StatusCode() int { return e.status }
+func (e myError) Error() string     { return "test error" }
+func (e myError) StatusCode() int   { return e.status }
+func (e myError) DetailMsg() string { return e.detail }
+func (e myError) Unwrap() error     { return HTTPError(e.err) }
 
 func TestErrorHandler(t *testing.T) {
 	t.Run("basic error", func(t *testing.T) {
@@ -39,7 +44,7 @@ func TestErrorHandler(t *testing.T) {
 		require.Equal(t, http.StatusNotFound, errResponse.(HTTPError).StatusCode())
 	})
 
-	t.Run("error with status ", func(t *testing.T) {
+	t.Run("error with status", func(t *testing.T) {
 		err := myError{
 			status: http.StatusNotFound,
 		}
@@ -50,6 +55,18 @@ func TestErrorHandler(t *testing.T) {
 		require.Equal(t, http.StatusNotFound, errResponse.(HTTPError).StatusCode())
 	})
 
+	t.Run("error with detail", func(t *testing.T) {
+		err := myError{
+			detail: "my detail",
+		}
+		errResponse := ErrorHandler(err)
+		require.ErrorAs(t, errResponse, &HTTPError{})
+		require.Contains(t, errResponse.Error(), "Internal Server Error")
+		require.Contains(t, errResponse.Error(), "500")
+		require.Contains(t, errResponse.Error(), "my detail")
+		require.Equal(t, http.StatusInternalServerError, errResponse.(HTTPError).StatusCode())
+	})
+
 	t.Run("conflict error", func(t *testing.T) {
 		err := ConflictError{
 			Err: errors.New("Conflict"),

examples/basic/main.go

@@ -22,6 +22,22 @@ type MyResponse struct {
 	BestFramework string `json:"best"`
 }
 
+type MyError struct {
+	Err     error  `json:"error"`
+	Message string `json:"message"`
+}
+
+var _ fuego.ErrorWithStatus = MyError{}
+var _ fuego.ErrorWithDetail = MyError{}
+
+func (e MyError) Error() string { return e.Err.Error() }
+
+func (e MyError) StatusCode() int { return http.StatusTeapot }
+
+func (e MyError) DetailMsg() string {
+	return strings.Split(e.Error(), " ")[1]
+}
+
 func main() {
 	s := fuego.NewServer(
 		fuego.WithAddr("localhost:8088"),
@@ -59,6 +75,10 @@ func main() {
 		w.Write([]byte("Hello, World!"))
 	})
 
+	fuego.Get(s, "/custom-err", func(c *fuego.ContextNoBody) (string, error) {
+		return "hello", MyError{Err: errors.New("my error")}
+	})
+
 	s.Run()
 }