feat(errors): add ErrorOr for default

Author: searKing

go/errors/decorator.go

@@ -44,3 +44,14 @@ func (hds HandlerDecorators) WrapHandler(next HandlerFunc) HandlerFunc {
 func (hds HandlerDecorators) WrapError(err error) error {
 	return hds.WrapHandler(func(err error) error { return err })(err)
 }
+
+// ErrorOr applies all decorators in the slice, in reverse order, to the error.
+// If the error is not handled, returns the default error.
+func (hds HandlerDecorators) ErrorOr(err error, defaultErr error) error {
+	return hds.WrapHandler(func(err error) error {
+		if err == nil {
+			return nil
+		}
+		return defaultErr
+	})(err)
+}

go/errors/decorator_test.go

@@ -169,3 +169,14 @@ func TestHandlerDecorators_WrapError(t *testing.T) {
 		t.Errorf("Wrapped error does not contain the original error.")
 	}
 }
+
+func TestHandlerDecorators_ErrorOr(t *testing.T) {
+	originalErr := errors.New("test error")
+
+	decorators := errors_.HandlerDecorators{}
+	resultErr := decorators.ErrorOr(originalErr, errors.New("default error"))
+	expectedErr := "default error"
+	if resultErr.Error() != expectedErr {
+		t.Errorf("Expected error '%s', but got '%s'", expectedErr, resultErr.Error())
+	}
+}