From 76b7d23a1092bdc13aaf8467079f82c8e6f4a409 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pedro=20J=2E=20Est=C3=A9banez?= <pedrojrulez@gmail.com>
Date: Tue, 14 Sep 2021 13:05:45 +0200
Subject: [PATCH] Unify determination of default property values

---
 editor/editor_inspector.cpp      | 177 ++---------------------------
 editor/editor_inspector.h        |   3 -
 editor/scene_tree_dock.cpp       |  21 ++--
 scene/property_utils.cpp         | 186 +++++++++++++++++++++++++++++++
 scene/property_utils.h           |  51 +++++++++
 scene/resources/packed_scene.cpp | 180 +++++++-----------------------
 scene/resources/packed_scene.h   |  15 ++-
 7 files changed, 301 insertions(+), 332 deletions(-)
 create mode 100644 scene/property_utils.cpp
 create mode 100644 scene/property_utils.h

diff --git a/editor/editor_inspector.cpp b/editor/editor_inspector.cpp
index 88e8f9120d3..5986bce1c3c 100644
--- a/editor/editor_inspector.cpp
+++ b/editor/editor_inspector.cpp
@@ -29,12 +29,14 @@
 /*************************************************************************/
 
 #include "editor_inspector.h"
+
 #include "array_property_edit.h"
 #include "dictionary_property_edit.h"
 #include "editor_feature_profile.h"
 #include "editor_node.h"
 #include "editor_scale.h"
 #include "multi_node_edit.h"
+#include "scene/property_utils.h"
 #include "scene/resources/packed_scene.h"
 
 Size2 EditorProperty::get_minimum_size() const {
@@ -318,177 +320,12 @@ bool EditorProperty::is_read_only() const {
 	return read_only;
 }
 
-bool EditorPropertyRevert::may_node_be_in_instance(Node *p_node) {
-	Node *edited_scene = EditorNode::get_singleton()->get_edited_scene();
-
-	bool might_be = false;
-	Node *node = p_node;
-
-	while (node) {
-		if (node == edited_scene) {
-			if (node->get_scene_inherited_state().is_valid()) {
-				might_be = true;
-				break;
-			}
-			might_be = false;
-			break;
-		}
-		if (node->get_scene_instance_state().is_valid()) {
-			might_be = true;
-			break;
-		}
-		node = node->get_owner();
-	}
-
-	return might_be; // or might not be
-}
-
-bool EditorPropertyRevert::get_instanced_node_original_property(Node *p_node, const StringName &p_prop, Variant &value, bool p_check_class_default) {
-	Node *node = p_node;
-	Node *orig = node;
-
-	Node *edited_scene = EditorNode::get_singleton()->get_edited_scene();
-
-	bool found = false;
-
-	while (node) {
-		Ref<SceneState> ss;
-
-		if (node == edited_scene) {
-			ss = node->get_scene_inherited_state();
-
-		} else {
-			ss = node->get_scene_instance_state();
-		}
-
-		if (ss.is_valid()) {
-			NodePath np = node->get_path_to(orig);
-			int node_idx = ss->find_node_by_path(np);
-			if (node_idx >= 0) {
-				bool lfound = false;
-				Variant lvar;
-				lvar = ss->get_property_value(node_idx, p_prop, lfound);
-				if (lfound) {
-					found = true;
-					value = lvar;
-				}
-			}
-		}
-		if (node == edited_scene) {
-			//just in case
-			break;
-		}
-		node = node->get_owner();
-	}
-
-	if (p_check_class_default && !found && p_node) {
-		//if not found, try default class value
-		Variant attempt = ClassDB::class_get_default_property_value(p_node->get_class_name(), p_prop);
-		if (attempt.get_type() != Variant::NIL) {
-			found = true;
-			value = attempt;
-		}
-	}
-
-	return found;
-}
-
-bool EditorPropertyRevert::is_node_property_different(Node *p_node, const Variant &p_current, const Variant &p_orig) {
-	// this is a pretty difficult function, because a property may not be saved but may have
-	// the flag to not save if one or if zero
-
-	//make sure there is an actual state
-	{
-		Node *node = p_node;
-		if (!node) {
-			return false;
-		}
-
-		Node *edited_scene = EditorNode::get_singleton()->get_edited_scene();
-		bool found_state = false;
-
-		while (node) {
-			Ref<SceneState> ss;
-
-			if (node == edited_scene) {
-				ss = node->get_scene_inherited_state();
-
-			} else {
-				ss = node->get_scene_instance_state();
-			}
-
-			if (ss.is_valid()) {
-				found_state = true;
-				break;
-			}
-			if (node == edited_scene) {
-				//just in case
-				break;
-			}
-			node = node->get_owner();
-		}
-
-		if (!found_state) {
-			return false; //pointless to check if we are not comparing against anything.
-		}
-	}
-
-	return is_property_value_different(p_current, p_orig);
-}
-
-bool EditorPropertyRevert::is_property_value_different(const Variant &p_a, const Variant &p_b) {
-	if (p_a.get_type() == Variant::REAL && p_b.get_type() == Variant::REAL) {
-		//this must be done because, as some scenes save as text, there might be a tiny difference in floats due to numerical error
-		return !Math::is_equal_approx((float)p_a, (float)p_b);
-	} else {
-		return p_a != p_b;
-	}
-}
-
 Variant EditorPropertyRevert::get_property_revert_value(Object *p_object, const StringName &p_property) {
-	// If the object implements property_can_revert, rely on that completely
-	// (i.e. don't then try to revert to default value - the property_get_revert implementation
-	// can do that if so desired)
 	if (p_object->has_method("property_can_revert") && p_object->call("property_can_revert", p_property)) {
 		return p_object->call("property_get_revert", p_property);
 	}
 
-	Ref<Script> scr = p_object->get_script();
-	Node *node = Object::cast_to<Node>(p_object);
-	if (node && EditorPropertyRevert::may_node_be_in_instance(node)) {
-		//if this node is an instance or inherits, but it has a script attached which is unrelated
-		//to the one set for the parent and also has a default value for the property, consider that
-		//has precedence over the value from the parent, because that is an explicit source of defaults
-		//closer in the tree to the current node
-		bool ignore_parent = false;
-		if (scr.is_valid()) {
-			Variant sorig;
-			if (EditorPropertyRevert::get_instanced_node_original_property(node, "script", sorig) && !scr->inherits_script(sorig)) {
-				Variant dummy;
-				if (scr->get_property_default_value(p_property, dummy)) {
-					ignore_parent = true;
-				}
-			}
-		}
-
-		if (!ignore_parent) {
-			//check for difference including instantiation
-			Variant vorig;
-			if (EditorPropertyRevert::get_instanced_node_original_property(node, p_property, vorig, false)) {
-				return vorig;
-			}
-		}
-	}
-
-	if (scr.is_valid()) {
-		Variant orig_value;
-		if (scr->get_property_default_value(p_property, orig_value)) {
-			return orig_value;
-		}
-	}
-
-	//report default class value instead
-	return ClassDB::class_get_default_property_value(p_object->get_class_name(), p_property);
+	return PropertyUtils::get_property_default_value(p_object, p_property);
 }
 
 bool EditorPropertyRevert::can_property_revert(Object *p_object, const StringName &p_property) {
@@ -497,7 +334,7 @@ bool EditorPropertyRevert::can_property_revert(Object *p_object, const StringNam
 		return false;
 	}
 	Variant current_value = p_object->get(p_property);
-	return EditorPropertyRevert::is_property_value_different(current_value, revert_value);
+	return PropertyUtils::is_property_value_different(current_value, revert_value);
 }
 
 void EditorProperty::update_reload_status() {
@@ -505,10 +342,10 @@ void EditorProperty::update_reload_status() {
 		return; //no property, so nothing to do
 	}
 
-	bool has_reload = EditorPropertyRevert::can_property_revert(object, property);
+	bool new_can_revert = EditorPropertyRevert::can_property_revert(object, property);
 
-	if (has_reload != can_revert) {
-		can_revert = has_reload;
+	if (new_can_revert != can_revert) {
+		can_revert = new_can_revert;
 		update();
 	}
 }
diff --git a/editor/editor_inspector.h b/editor/editor_inspector.h
index 3a0038f2c94..bf27ccfd97c 100644
--- a/editor/editor_inspector.h
+++ b/editor/editor_inspector.h
@@ -39,7 +39,6 @@ class UndoRedo;
 
 class EditorPropertyRevert {
 public:
-	static bool may_node_be_in_instance(Node *p_node);
 	static bool get_instanced_node_original_property(Node *p_node, const StringName &p_prop, Variant &value, bool p_check_class_default = true);
 	static bool is_node_property_different(Node *p_node, const Variant &p_current, const Variant &p_orig);
 	static bool is_property_value_different(const Variant &p_a, const Variant &p_b);
@@ -81,8 +80,6 @@ private:
 	bool use_folding;
 	bool draw_top_bg;
 
-	bool _is_property_different(const Variant &p_current, const Variant &p_orig);
-	bool _get_instanced_node_original_property(const StringName &p_prop, Variant &value);
 	void _focusable_focused(int p_index);
 
 	bool selectable;
diff --git a/editor/scene_tree_dock.cpp b/editor/scene_tree_dock.cpp
index 4d70f63b37d..d1bd68b331f 100644
--- a/editor/scene_tree_dock.cpp
+++ b/editor/scene_tree_dock.cpp
@@ -34,7 +34,6 @@
 #include "core/os/input.h"
 #include "core/os/keyboard.h"
 #include "core/project_settings.h"
-
 #include "editor/editor_feature_profile.h"
 #include "editor/editor_node.h"
 #include "editor/editor_scale.h"
@@ -46,6 +45,7 @@
 #include "editor/plugins/spatial_editor_plugin.h"
 #include "editor/script_editor_debugger.h"
 #include "scene/main/viewport.h"
+#include "scene/property_utils.h"
 #include "scene/resources/packed_scene.h"
 
 void SceneTreeDock::_nodes_drag_begin() {
@@ -3086,7 +3086,9 @@ void SceneTreeDock::_clear_clipboard() {
 void SceneTreeDock::_create_remap_for_node(Node *p_node, Map<RES, RES> &r_remap) {
 	List<PropertyInfo> props;
 	p_node->get_property_list(&props);
-	bool is_instanced = EditorPropertyRevert::may_node_be_in_instance(p_node);
+
+	Vector<SceneState::PackState> states_stack;
+	bool states_stack_ready = false;
 
 	for (List<PropertyInfo>::Element *E = props.front(); E; E = E->next()) {
 		if (!(E->get().usage & PROPERTY_USAGE_STORAGE)) {
@@ -3097,13 +3099,14 @@ void SceneTreeDock::_create_remap_for_node(Node *p_node, Map<RES, RES> &r_remap)
 		if (v.is_ref()) {
 			RES res = v;
 			if (res.is_valid()) {
-				if (is_instanced) {
-					Variant orig;
-					if (EditorPropertyRevert::get_instanced_node_original_property(p_node, E->get().name, orig)) {
-						if (!EditorPropertyRevert::is_node_property_different(p_node, v, orig)) {
-							continue;
-						}
-					}
+				if (!states_stack_ready) {
+					states_stack = PropertyUtils::get_node_states_stack(p_node);
+					states_stack_ready = true;
+				}
+
+				Variant orig = PropertyUtils::get_property_default_value(p_node, E->get().name, &states_stack);
+				if (!PropertyUtils::is_property_value_different(v, orig)) {
+					continue;
 				}
 
 				if ((res->get_path() == "" || res->get_path().find("::") > -1) && !r_remap.has(res)) {
diff --git a/scene/property_utils.cpp b/scene/property_utils.cpp
new file mode 100644
index 00000000000..4e1cb50a168
--- /dev/null
+++ b/scene/property_utils.cpp
@@ -0,0 +1,186 @@
+/*************************************************************************/
+/*  property_utils.cpp                                                   */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#include "property_utils.h"
+
+#include "core/core_string_names.h"
+#include "core/engine.h"
+#include "core/local_vector.h"
+#include "editor/editor_node.h"
+#include "scene/resources/packed_scene.h"
+
+bool PropertyUtils::is_property_value_different(const Variant &p_a, const Variant &p_b) {
+	if (p_a.get_type() == Variant::REAL && p_b.get_type() == Variant::REAL) {
+		//this must be done because, as some scenes save as text, there might be a tiny difference in floats due to numerical error
+		return !Math::is_equal_approx((float)p_a, (float)p_b);
+	} else {
+		// For our purposes, treating null object as NIL is the right thing to do
+		const Variant &a = p_a.get_type() == Variant::OBJECT && (Object *)p_a == nullptr ? Variant() : p_a;
+		const Variant &b = p_b.get_type() == Variant::OBJECT && (Object *)p_b == nullptr ? Variant() : p_b;
+		return a != b;
+	}
+}
+
+Variant PropertyUtils::get_property_default_value(const Object *p_object, const StringName &p_property, const Vector<SceneState::PackState> *p_states_stack_cache, bool p_update_exports, const Node *p_owner, bool *r_is_class_default) {
+	// This function obeys the way property values are set when an object is instantiated,
+	// which is the following (the latter wins):
+	// 1. Default value from builtin class
+	// 2. Default value from script exported variable (from the topmost script)
+	// 3. Value overrides from the instantiation/inheritance stack
+
+	if (r_is_class_default) {
+		*r_is_class_default = false;
+	}
+
+	Ref<Script> topmost_script;
+
+	if (const Node *node = Object::cast_to<Node>(p_object)) {
+		// Check inheritance/instantiation ancestors
+		const Vector<SceneState::PackState> &states_stack = p_states_stack_cache ? *p_states_stack_cache : PropertyUtils::get_node_states_stack(node, p_owner);
+		for (int i = 0; i < states_stack.size(); ++i) {
+			const SceneState::PackState &ia = states_stack[i];
+			bool found = false;
+			Variant value_in_ancestor = ia.state->get_property_value(ia.node, p_property, found);
+			if (found) {
+				return value_in_ancestor;
+			}
+			// Save script for later
+			bool has_script = false;
+			Variant script = ia.state->get_property_value(ia.node, CoreStringNames::get_singleton()->_script, has_script);
+			if (has_script) {
+				Ref<Script> scr = script;
+				if (scr.is_valid()) {
+					topmost_script = scr;
+				}
+			}
+		}
+	}
+
+	// Let's see what default is set by the topmost script having a default, if any
+	if (topmost_script.is_null()) {
+		topmost_script = p_object->get_script();
+	}
+	if (topmost_script.is_valid()) {
+		Variant default_value;
+		// Should be called in the editor only and not at runtime,
+		// otherwise it can cause problems because of missing instance state support.
+		if (p_update_exports && Engine::get_singleton()->is_editor_hint()) {
+			topmost_script->update_exports();
+		}
+		if (topmost_script->get_property_default_value(p_property, default_value)) {
+			return default_value;
+		}
+	}
+
+	// Fall back to the default from the native class
+	if (r_is_class_default) {
+		*r_is_class_default = true;
+	}
+	return ClassDB::class_get_default_property_value(p_object->get_class_name(), p_property);
+}
+
+// Like SceneState::PackState, but using a raw pointer to avoid the cost of
+// updating the reference count during the internal work of the functions below
+namespace {
+struct _FastPackState {
+	SceneState *state = nullptr;
+	int node = -1;
+};
+} // namespace
+
+static bool _collect_inheritance_chain(const Ref<SceneState> &p_state, const NodePath &p_path, LocalVector<_FastPackState> &r_states_stack) {
+	bool found = false;
+
+	LocalVector<_FastPackState> inheritance_states;
+
+	Ref<SceneState> state = p_state;
+	while (state.is_valid()) {
+		int node = state->find_node_by_path(p_path);
+		if (node >= 0) {
+			// This one has state for this node
+			inheritance_states.push_back({ state.ptr(), node });
+			found = true;
+		}
+		state = state->get_base_scene_state();
+	}
+
+	for (int i = inheritance_states.size() - 1; i >= 0; --i) {
+		r_states_stack.push_back(inheritance_states[i]);
+	}
+
+	return found;
+}
+
+Vector<SceneState::PackState> PropertyUtils::get_node_states_stack(const Node *p_node, const Node *p_owner, bool *r_instanced_by_owner) {
+	if (r_instanced_by_owner) {
+		*r_instanced_by_owner = true;
+	}
+
+	LocalVector<_FastPackState> states_stack;
+	{
+		const Node *owner = p_owner;
+#ifdef TOOLS_ENABLED
+		if (!p_owner && Engine::get_singleton()->is_editor_hint()) {
+			owner = EditorNode::get_singleton()->get_edited_scene();
+		}
+#endif
+
+		const Node *n = p_node;
+		while (n) {
+			if (n == owner) {
+				const Ref<SceneState> &state = n->get_scene_inherited_state();
+				if (_collect_inheritance_chain(state, n->get_path_to(p_node), states_stack)) {
+					if (r_instanced_by_owner) {
+						*r_instanced_by_owner = false;
+					}
+				}
+				break;
+			} else if (n->get_filename() != String()) {
+				const Ref<SceneState> &state = n->get_scene_instance_state();
+				_collect_inheritance_chain(state, n->get_path_to(p_node), states_stack);
+			}
+			n = n->get_owner();
+		}
+	}
+
+	// Convert to the proper type for returning, inverting the vector on the go
+	// (it was more convenient to fill the vector in reverse order)
+	Vector<SceneState::PackState> states_stack_ret;
+	{
+		states_stack_ret.resize(states_stack.size());
+		_FastPackState *ps = states_stack.ptr();
+		for (int i = states_stack.size() - 1; i >= 0; --i) {
+			states_stack_ret.write[i].state.reference_ptr(ps->state);
+			states_stack_ret.write[i].node = ps->node;
+			++ps;
+		}
+	}
+	return states_stack_ret;
+}
diff --git a/scene/property_utils.h b/scene/property_utils.h
new file mode 100644
index 00000000000..2a1151fc886
--- /dev/null
+++ b/scene/property_utils.h
@@ -0,0 +1,51 @@
+/*************************************************************************/
+/*  property_utils.h                                                     */
+/*************************************************************************/
+/*                       This file is part of:                           */
+/*                           GODOT ENGINE                                */
+/*                      https://godotengine.org                          */
+/*************************************************************************/
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
+/*                                                                       */
+/* Permission is hereby granted, free of charge, to any person obtaining */
+/* a copy of this software and associated documentation files (the       */
+/* "Software"), to deal in the Software without restriction, including   */
+/* without limitation the rights to use, copy, modify, merge, publish,   */
+/* distribute, sublicense, and/or sell copies of the Software, and to    */
+/* permit persons to whom the Software is furnished to do so, subject to */
+/* the following conditions:                                             */
+/*                                                                       */
+/* The above copyright notice and this permission notice shall be        */
+/* included in all copies or substantial portions of the Software.       */
+/*                                                                       */
+/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
+/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
+/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
+/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
+/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
+/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
+/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
+/*************************************************************************/
+
+#ifndef PROPERTY_UTILS_H
+#define PROPERTY_UTILS_H
+
+#include "scene/main/node.h"
+#include "scene/resources/packed_scene.h"
+
+class PropertyUtils {
+public:
+	static bool is_property_value_different(const Variant &p_a, const Variant &p_b);
+	// Gets the most pure default value, the one that would be set when the node has just been instantiated
+	static Variant get_property_default_value(const Object *p_object, const StringName &p_property, const Vector<SceneState::PackState> *p_states_stack_cache = nullptr, bool p_update_exports = false, const Node *p_owner = nullptr, bool *r_is_class_default = nullptr);
+
+	// Gets the instance/inheritance states of this node, in order of precedence,
+	// that is, from the topmost (the most able to override values) to the lowermost
+	// (Note that in nested instancing the one with the greatest precedence is the furthest
+	// in the tree, since every owner found while traversing towards the root gets a chance
+	// to override property values.)
+	static Vector<SceneState::PackState> get_node_states_stack(const Node *p_node, const Node *p_owner = nullptr, bool *r_instanced_by_owner = nullptr);
+};
+
+#endif // PROPERTY_UTILS_H
diff --git a/scene/resources/packed_scene.cpp b/scene/resources/packed_scene.cpp
index cf4b799bfd9..6692619c17f 100644
--- a/scene/resources/packed_scene.cpp
+++ b/scene/resources/packed_scene.cpp
@@ -34,10 +34,12 @@
 #include "core/engine.h"
 #include "core/io/resource_loader.h"
 #include "core/project_settings.h"
+#include "editor/editor_inspector.h"
 #include "scene/2d/node_2d.h"
 #include "scene/3d/spatial.h"
 #include "scene/gui/control.h"
 #include "scene/main/instance_placeholder.h"
+#include "scene/property_utils.h"
 
 #define PACKED_SCENE_VERSION 2
 
@@ -413,61 +415,22 @@ Error SceneState::_parse_node(Node *p_owner, Node *p_node, int p_parent_idx, Map
 	// with the instance states, we can query for identical properties/groups
 	// and only save what has changed
 
-	List<PackState> pack_state_stack;
+	bool instanced_by_owner = false;
+	Vector<SceneState::PackState> states_stack = PropertyUtils::get_node_states_stack(p_node, p_owner, &instanced_by_owner);
 
-	bool instanced_by_owner = true;
-
-	{
-		Node *n = p_node;
-
-		while (n) {
-			if (n == p_owner) {
-				Ref<SceneState> state = n->get_scene_inherited_state();
-				if (state.is_valid()) {
-					int node = state->find_node_by_path(n->get_path_to(p_node));
-					if (node >= 0) {
-						//this one has state for this node, save
-						PackState ps;
-						ps.node = node;
-						ps.state = state;
-						pack_state_stack.push_back(ps);
-						instanced_by_owner = false;
-					}
-				}
-
-				if (p_node->get_filename() != String() && p_node->get_owner() == p_owner && instanced_by_owner) {
-					if (p_node->get_scene_instance_load_placeholder()) {
-						//it's a placeholder, use the placeholder path
-						nd.instance = _vm_get_variant(p_node->get_filename(), variant_map);
-						nd.instance |= FLAG_INSTANCE_IS_PLACEHOLDER;
-					} else {
-						//must instance ourselves
-						Ref<PackedScene> instance = ResourceLoader::load(p_node->get_filename());
-						if (!instance.is_valid()) {
-							return ERR_CANT_OPEN;
-						}
-
-						nd.instance = _vm_get_variant(instance, variant_map);
-					}
-				}
-				n = nullptr;
-			} else {
-				if (n->get_filename() != String()) {
-					//is an instance
-					Ref<SceneState> state = n->get_scene_instance_state();
-					if (state.is_valid()) {
-						int node = state->find_node_by_path(n->get_path_to(p_node));
-						if (node >= 0) {
-							//this one has state for this node, save
-							PackState ps;
-							ps.node = node;
-							ps.state = state;
-							pack_state_stack.push_back(ps);
-						}
-					}
-				}
-				n = n->get_owner();
+	if (p_node->get_filename() != String() && p_node->get_owner() == p_owner && instanced_by_owner) {
+		if (p_node->get_scene_instance_load_placeholder()) {
+			//it's a placeholder, use the placeholder path
+			nd.instance = _vm_get_variant(p_node->get_filename(), variant_map);
+			nd.instance |= FLAG_INSTANCE_IS_PLACEHOLDER;
+		} else {
+			//must instance ourselves
+			Ref<PackedScene> instance = ResourceLoader::load(p_node->get_filename());
+			if (!instance.is_valid()) {
+				return ERR_CANT_OPEN;
 			}
+
+			nd.instance = _vm_get_variant(instance, variant_map);
 		}
 	}
 
@@ -476,90 +439,23 @@ Error SceneState::_parse_node(Node *p_owner, Node *p_node, int p_parent_idx, Map
 
 	List<PropertyInfo> plist;
 	p_node->get_property_list(&plist);
-	StringName type = p_node->get_class();
-
-	Ref<Script> script = p_node->get_script();
-	if (Engine::get_singleton()->is_editor_hint() && script.is_valid()) {
-		// Should be called in the editor only and not at runtime,
-		// otherwise it can cause problems because of missing instance state support.
-		script->update_exports();
-	}
 
 	for (List<PropertyInfo>::Element *E = plist.front(); E; E = E->next()) {
 		if (!(E->get().usage & PROPERTY_USAGE_STORAGE)) {
 			continue;
 		}
 
+		// If instance or inheriting, not saving if property requested so, or it's meta
+		if (states_stack.size() && ((E->get().usage & PROPERTY_USAGE_NO_INSTANCE_STATE) || E->get().name == "__meta__")) {
+			continue;
+		}
+
 		String name = E->get().name;
-		Variant value = p_node->get(E->get().name);
+		Variant value = p_node->get(name);
 
-		bool isdefault = false;
-		Variant default_value = ClassDB::class_get_default_property_value(type, name);
-
-		if (default_value.get_type() != Variant::NIL) {
-			isdefault = bool(Variant::evaluate(Variant::OP_EQUAL, value, default_value));
-		}
-
-		if (!isdefault && script.is_valid() && script->get_property_default_value(name, default_value)) {
-			isdefault = bool(Variant::evaluate(Variant::OP_EQUAL, value, default_value));
-		}
-		// the version above makes more sense, because it does not rely on placeholder or usage flag
-		// in the script, just the default value function.
-		// if (E->get().usage & PROPERTY_USAGE_SCRIPT_DEFAULT_VALUE) {
-		// 	isdefault = true; //is script default value
-		// }
-
-		if (pack_state_stack.size()) {
-			// we are on part of an instanced subscene
-			// or part of instanced scene.
-			// only save what has been changed
-			// only save changed properties in instance
-
-			if ((E->get().usage & PROPERTY_USAGE_NO_INSTANCE_STATE) || E->get().name == "__meta__") {
-				//property has requested that no instance state is saved, sorry
-				//also, meta won't be overridden or saved
-				continue;
-			}
-
-			bool exists = false;
-			Variant original;
-
-			for (List<PackState>::Element *F = pack_state_stack.back(); F; F = F->prev()) {
-				//check all levels of pack to see if the property exists somewhere
-				const PackState &ps = F->get();
-
-				original = ps.state->get_property_value(ps.node, E->get().name, exists);
-				if (exists) {
-					break;
-				}
-			}
-
-			if (exists) {
-				//check if already exists and did not change
-				if (value.get_type() == Variant::REAL && original.get_type() == Variant::REAL) {
-					//this must be done because, as some scenes save as text, there might be a tiny difference in floats due to numerical error
-					float a = value;
-					float b = original;
-
-					if (Math::is_equal_approx(a, b)) {
-						continue;
-					}
-				} else if (bool(Variant::evaluate(Variant::OP_EQUAL, value, original))) {
-					continue;
-				}
-			}
-
-			if (!exists && isdefault) {
-				//does not exist in original node, but it's the default value
-				//so safe to skip too.
-				continue;
-			}
-
-		} else {
-			if (isdefault) {
-				//it's the default value, no point in saving it
-				continue;
-			}
+		Variant default_value = PropertyUtils::get_property_default_value(p_node, name, &states_stack, true);
+		if (!PropertyUtils::is_property_value_different(value, default_value)) {
+			continue;
 		}
 
 		NodeData::Property prop;
@@ -585,10 +481,10 @@ Error SceneState::_parse_node(Node *p_owner, Node *p_node, int p_parent_idx, Map
 		*/
 
 		bool skip = false;
-		for (List<PackState>::Element *F = pack_state_stack.front(); F; F = F->next()) {
+		for (int i = 0; i < states_stack.size(); ++i) {
+			const auto &ia = states_stack[i];
 			//check all levels of pack to see if the group was added somewhere
-			const PackState &ps = F->get();
-			if (ps.state->is_node_in_group(ps.node, gi.name)) {
+			if (ia.state->is_node_in_group(ia.node, gi.name)) {
 				skip = true;
 				break;
 			}
@@ -618,7 +514,7 @@ Error SceneState::_parse_node(Node *p_owner, Node *p_node, int p_parent_idx, Map
 
 	// Save the right type. If this node was created by an instance
 	// then flag that the node should not be created but reused
-	if (pack_state_stack.empty() && !is_editable_instance) {
+	if (states_stack.empty() && !is_editable_instance) {
 		//this node is not part of an instancing process, so save the type
 		nd.type = _nm_get_string(p_node->get_class(), name_map);
 	} else {
@@ -932,7 +828,7 @@ void SceneState::clear() {
 	base_scene_idx = -1;
 }
 
-Ref<SceneState> SceneState::_get_base_scene_state() const {
+Ref<SceneState> SceneState::get_base_scene_state() const {
 	if (base_scene_idx >= 0) {
 		Ref<PackedScene> ps = variants[base_scene_idx];
 		if (ps.is_valid()) {
@@ -947,8 +843,8 @@ int SceneState::find_node_by_path(const NodePath &p_node) const {
 	ERR_FAIL_COND_V_MSG(node_path_cache.size() == 0, -1, "This operation requires the node cache to have been built.");
 
 	if (!node_path_cache.has(p_node)) {
-		if (_get_base_scene_state().is_valid()) {
-			int idx = _get_base_scene_state()->find_node_by_path(p_node);
+		if (get_base_scene_state().is_valid()) {
+			int idx = get_base_scene_state()->find_node_by_path(p_node);
 			if (idx != -1) {
 				int rkey = _find_base_scene_node_remap_key(idx);
 				if (rkey == -1) {
@@ -963,11 +859,11 @@ int SceneState::find_node_by_path(const NodePath &p_node) const {
 
 	int nid = node_path_cache[p_node];
 
-	if (_get_base_scene_state().is_valid() && !base_scene_node_remap.has(nid)) {
+	if (get_base_scene_state().is_valid() && !base_scene_node_remap.has(nid)) {
 		//for nodes that _do_ exist in current scene, still try to look for
 		//the node in the instanced scene, as a property may be missing
 		//from the local one
-		int idx = _get_base_scene_state()->find_node_by_path(p_node);
+		int idx = get_base_scene_state()->find_node_by_path(p_node);
 		if (idx != -1) {
 			base_scene_node_remap[nid] = idx;
 		}
@@ -1007,7 +903,7 @@ Variant SceneState::get_property_value(int p_node, const StringName &p_property,
 	//property not found, try on instance
 
 	if (base_scene_node_remap.has(p_node)) {
-		return _get_base_scene_state()->get_property_value(base_scene_node_remap[p_node], p_property, found);
+		return get_base_scene_state()->get_property_value(base_scene_node_remap[p_node], p_property, found);
 	}
 
 	return Variant();
@@ -1026,7 +922,7 @@ bool SceneState::is_node_in_group(int p_node, const StringName &p_group) const {
 	}
 
 	if (base_scene_node_remap.has(p_node)) {
-		return _get_base_scene_state()->is_node_in_group(base_scene_node_remap[p_node], p_group);
+		return get_base_scene_state()->is_node_in_group(base_scene_node_remap[p_node], p_group);
 	}
 
 	return false;
@@ -1065,7 +961,7 @@ bool SceneState::is_connection(int p_node, const StringName &p_signal, int p_to_
 	}
 
 	if (base_scene_node_remap.has(p_node) && base_scene_node_remap.has(p_to_node)) {
-		return _get_base_scene_state()->is_connection(base_scene_node_remap[p_node], p_signal, base_scene_node_remap[p_to_node], p_to_method);
+		return get_base_scene_state()->is_connection(base_scene_node_remap[p_node], p_signal, base_scene_node_remap[p_to_node], p_to_method);
 	}
 
 	return false;
@@ -1483,7 +1379,7 @@ bool SceneState::has_connection(const NodePath &p_node_from, const StringName &p
 			}
 		}
 
-		ss = ss->_get_base_scene_state();
+		ss = ss->get_base_scene_state();
 	} while (ss.is_valid());
 
 	return false;
diff --git a/scene/resources/packed_scene.h b/scene/resources/packed_scene.h
index 68d7d232d31..11365728ffd 100644
--- a/scene/resources/packed_scene.h
+++ b/scene/resources/packed_scene.h
@@ -69,12 +69,6 @@ class SceneState : public Reference {
 		Vector<int> groups;
 	};
 
-	struct PackState {
-		Ref<SceneState> state;
-		int node;
-		PackState() { node = -1; }
-	};
-
 	Vector<NodeData> nodes;
 
 	struct ConnectionData {
@@ -95,8 +89,6 @@ class SceneState : public Reference {
 
 	uint64_t last_modified_time;
 
-	_FORCE_INLINE_ Ref<SceneState> _get_base_scene_state() const;
-
 	static bool disable_placeholders;
 
 	PoolVector<String> _get_node_groups(int p_idx) const;
@@ -120,6 +112,11 @@ public:
 		GEN_EDIT_STATE_MAIN,
 	};
 
+	struct PackState {
+		Ref<SceneState> state;
+		int node = -1;
+	};
+
 	static void set_disable_placeholders(bool p_disable);
 
 	int find_node_by_path(const NodePath &p_node) const;
@@ -140,6 +137,8 @@ public:
 	bool can_instance() const;
 	Node *instance(GenEditState p_edit_state) const;
 
+	Ref<SceneState> get_base_scene_state() const;
+
 	//unbuild API
 
 	int get_node_count() const;