keep default exported script values unless overriden, closes #8127

(cherry picked from commit 475e8b28b28962a24b783597f9a3cabf4a370dee)

core/object.h

@@ -91,6 +91,8 @@ enum PropertyUsageFlags {
 	PROPERTY_USAGE_STORE_IF_NULL = 16384,
 	PROPERTY_USAGE_ANIMATE_AS_TRIGGER = 32768,
 
+	PROPERTY_USAGE_SCRIPT_DEFAULT_VALUE = 1 << 17,
+
 	PROPERTY_USAGE_DEFAULT = PROPERTY_USAGE_STORAGE | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_NETWORK,
 	PROPERTY_USAGE_DEFAULT_INTL = PROPERTY_USAGE_STORAGE | PROPERTY_USAGE_EDITOR | PROPERTY_USAGE_NETWORK | PROPERTY_USAGE_INTERNATIONALIZED,
 	PROPERTY_USAGE_NOEDITOR = PROPERTY_USAGE_STORAGE | PROPERTY_USAGE_NETWORK,

core/script_language.cpp

@@ -277,8 +277,23 @@ ScriptDebugger::ScriptDebugger() {
 bool PlaceHolderScriptInstance::set(const StringName &p_name, const Variant &p_value) {
 
 	if (values.has(p_name)) {
+		Variant defval;
+		if (script->get_property_default_value(p_name, defval)) {
+			if (defval == p_value) {
+				values.erase(p_name);
+				return true;
+			}
+		}
 		values[p_name] = p_value;
 		return true;
+	} else {
+		Variant defval;
+		if (script->get_property_default_value(p_name, defval)) {
+			if (defval != p_value) {
+				values[p_name] = p_value;
+			}
+			return true;
+		}
 	}
 	return false;
 }
@@ -288,12 +303,22 @@ bool PlaceHolderScriptInstance::get(const StringName &p_name, Variant &r_ret) co
 		r_ret = values[p_name];
 		return true;
 	}
+
+	Variant defval;
+	if (script->get_property_default_value(p_name, defval)) {
+		r_ret = defval;
+		return true;
+	}
 	return false;
 }
 
 void PlaceHolderScriptInstance::get_property_list(List<PropertyInfo> *p_properties) const {
 
 	for (const List<PropertyInfo>::Element *E = properties.front(); E; E = E->next()) {
+		PropertyInfo pinfo = E->get();
+		if (!values.has(pinfo.name)) {
+			pinfo.usage |= PROPERTY_USAGE_SCRIPT_DEFAULT_VALUE;
+		}
 		p_properties->push_back(E->get());
 	}
 }
@@ -333,6 +358,14 @@ void PlaceHolderScriptInstance::update(const List<PropertyInfo> &p_properties, c
 
 		if (!new_values.has(E->key()))
 			to_remove.push_back(E->key());
+
+		Variant defval;
+		if (script->get_property_default_value(E->key(), defval)) {
+			//remove because it's the same as the default value
+			if (defval == E->get()) {
+				to_remove.push_back(E->key());
+			}
+		}
 	}
 
 	while (to_remove.size()) {

scene/resources/packed_scene.cpp

@@ -474,6 +474,9 @@ Error SceneState::_parse_node(Node *p_owner, Node *p_node, int p_parent_idx, Map
 
 		bool isdefault = ((E->get().usage & PROPERTY_USAGE_STORE_IF_NONZERO) && value.is_zero()) || ((E->get().usage & PROPERTY_USAGE_STORE_IF_NONONE) && value.is_one());
 
+		if (E->get().usage & PROPERTY_USAGE_SCRIPT_DEFAULT_VALUE) {
+			isdefault = true; //is script default value
+		}
 		//		if (nd.instance<0 && ((E->get().usage & PROPERTY_USAGE_STORE_IF_NONZERO) && value.is_zero()) || ((E->get().usage & PROPERTY_USAGE_STORE_IF_NONONE) && value.is_one())) {
 		//			continue;
 		//		}

scene/resources/texture.cpp

@@ -188,6 +188,7 @@ void ImageTexture::create(int p_width, int p_height, Image::Format p_format, uin
 }
 void ImageTexture::create_from_image(const Image &p_image, uint32_t p_flags) {
 
+	ERR_FAIL_COND(p_image.empty());
 	flags = p_flags;
 	w = p_image.get_width();
 	h = p_image.get_height();