GDExtension: Allow directly getting ObjectID from Variant

Author: dsnopek

core/extension/gdextension_interface.cpp

@@ -507,6 +507,14 @@ static GDExtensionBool gdextension_variant_has_key(GDExtensionConstVariantPtr p_
 	return ret;
 }
 
+static GDObjectInstanceID gdextension_variant_get_object_instance_id(GDExtensionConstVariantPtr p_self) {
+	const Variant *self = (const Variant *)p_self;
+	if (likely(self->get_type() == Variant::OBJECT)) {
+		return self->operator ObjectID();
+	}
+	return 0;
+}
+
 static void gdextension_variant_get_type_name(GDExtensionVariantType p_type, GDExtensionUninitializedVariantPtr r_ret) {
 	String name = Variant::get_type_name((Variant::Type)p_type);
 	memnew_placement(r_ret, String(name));
@@ -1610,6 +1618,7 @@ void gdextension_setup_interface() {
 	REGISTER_INTERFACE_FUNC(variant_has_method);
 	REGISTER_INTERFACE_FUNC(variant_has_member);
 	REGISTER_INTERFACE_FUNC(variant_has_key);
+	REGISTER_INTERFACE_FUNC(variant_get_object_instance_id);
 	REGISTER_INTERFACE_FUNC(variant_get_type_name);
 	REGISTER_INTERFACE_FUNC(variant_can_convert);
 	REGISTER_INTERFACE_FUNC(variant_can_convert_strict);

core/extension/gdextension_interface.h

@@ -1307,6 +1307,21 @@ typedef GDExtensionBool (*GDExtensionInterfaceVariantHasMember)(GDExtensionVaria
  */
 typedef GDExtensionBool (*GDExtensionInterfaceVariantHasKey)(GDExtensionConstVariantPtr p_self, GDExtensionConstVariantPtr p_key, GDExtensionBool *r_valid);
 
+/**
+ * @name variant_get_object_instance_id
+ * @since 4.4
+ *
+ * Gets the object instance ID from a variant of type GDEXTENSION_VARIANT_TYPE_OBJECT.
+ *
+ * If the variant isn't of type GDEXTENSION_VARIANT_TYPE_OBJECT, then zero will be returned.
+ * The instance ID will be returned even if the object is no longer valid - use `object_get_instance_by_id()` to check if the object is still valid.
+ *
+ * @param p_self A pointer to the Variant.
+ *
+ * @return The instance ID for the contained object.
+ */
+typedef GDObjectInstanceID (*GDExtensionInterfaceVariantGetObjectInstanceId)(GDExtensionConstVariantPtr p_self);
+
 /**
  * @name variant_get_type_name
  * @since 4.1