feat(qmetaobject): add null and undefined functions to QJSValue

Author: Mikhail Zolotukhin

qmetaobject/src/qtdeclarative.rs

@@ -937,6 +937,18 @@ pub enum QJSValueSpecialValue {
 }
 
 impl QJSValue {
+    pub fn null() -> Self {
+        cpp!(unsafe [] -> QJSValue as "QJSValue" {
+            return QJSValue(QJSValue::SpecialValue::NullValue);
+        })
+    }
+
+    pub fn undefined() -> Self {
+        cpp!(unsafe [] -> QJSValue as "QJSValue" {
+            return QJSValue(QJSValue::SpecialValue::UndefinedValue);
+        })
+    }
+
     pub fn is_bool(&self) -> bool {
         cpp!(unsafe [self as "const QJSValue *"] -> bool as "bool" {
             return self->isBool();
@@ -1008,6 +1020,12 @@ impl QJSValue {
     }
 }
 
+impl Default for QJSValue {
+    fn default() -> Self {
+        QJSValue::undefined()
+    }
+}
+
 impl From<QString> for QJSValue {
     fn from(a: QString) -> QJSValue {
         cpp!(unsafe [a as "QString"] -> QJSValue as "QJSValue" {