Added more error handling and necessary functions

extensionElement.go

@@ -11,14 +11,25 @@ type ExtensionElement struct {
 }
 
 // NewExtensionElement creates a new ExtensionElement. It returns a
-// *ExtensionElement.
-func NewExtensionElement(name string, value any) *ExtensionElement {
-	return &ExtensionElement{XMLName: xml.Name{Local: name}, Value: value}
+// *ExtensionElement and an error.
+func NewExtensionElement(name string, value any) (*ExtensionElement, error) {
+	if name == "" {
+		return nil, errors.New("error adding extension attribute: name string empty")
+	}
+	if value == "" {
+		return nil, errors.New("error adding extension attribute: value string empty")
+	}
+
+	return &ExtensionElement{XMLName: xml.Name{Local: name}, Value: value}, nil
 }
 
 // Check checks the ExtensionElement for incompatibilities with RFC4287. It
 // returns an error.
 func (e *ExtensionElement) Check() error {
+	if e.XMLName.Local == "" {
+		return errors.New("xml name of extension empty")
+	}
+
 	if e.Value == nil {
 		return errors.New("value element of extension empty")
 	}