make InstancePlaceholder in charge of node reference resolution

scene/main/instance_placeholder.cpp

@@ -88,16 +88,16 @@ Node *InstancePlaceholder::create_instance(bool p_replace, const Ref<PackedScene
 	if (!ps.is_valid()) {
 		return nullptr;
 	}
-	Node *scene = ps->instantiate();
-	if (!scene) {
+	Node *instance = ps->instantiate();
+	if (!instance) {
 		return nullptr;
 	}
-	scene->set_name(get_name());
-	scene->set_multiplayer_authority(get_multiplayer_authority());
+	instance->set_name(get_name());
+	instance->set_multiplayer_authority(get_multiplayer_authority());
 	int pos = get_index();
 
 	for (const PropSet &E : stored_values) {
-		scene->set(E.name, E.value);
+		set_value_on_instance(this, instance, E);
 	}
 
 	if (p_replace) {
@@ -105,10 +105,125 @@ Node *InstancePlaceholder::create_instance(bool p_replace, const Ref<PackedScene
 		base->remove_child(this);
 	}
 
-	base->add_child(scene);
-	base->move_child(scene, pos);
+	base->add_child(instance);
+	base->move_child(instance, pos);
 
-	return scene;
+	return instance;
+}
+
+// This method will attempt to set the correct values on the placeholder instance
+// for regular types this is trivial and unnecessary.
+// For nodes however this becomes a bit tricky because they might now have existed until the instantiation,
+// so this method will try to find the correct nodes and resolve them.
+void InstancePlaceholder::set_value_on_instance(InstancePlaceholder *p_placeholder, Node *p_instance, const PropSet &p_set) {
+	bool is_valid;
+
+	// If we don't have any info, we can't do anything,
+	// so try setting the value directly.
+	Variant current = p_instance->get(p_set.name, &is_valid);
+	if (!is_valid) {
+		p_instance->set(p_set.name, p_set.value, &is_valid);
+		return;
+	}
+
+	Variant::Type current_type = current.get_type();
+	Variant::Type placeholder_type = p_set.value.get_type();
+
+	// Arrays are a special case, because their containing type might be different.
+	if (current_type != Variant::Type::ARRAY) {
+		// Check if the variant types match.
+		if (Variant::evaluate(Variant::OP_EQUAL, current_type, placeholder_type)) {
+			p_instance->set(p_set.name, p_set.value, &is_valid);
+			if (is_valid) {
+				return;
+			}
+			// Types match but setting failed? This is strange, so let's print a warning!
+			WARN_PRINT(vformat("Property '%s' with type '%s' could not be set when creating instance of '%s'.", p_set.name, Variant::get_type_name(current_type), p_placeholder->get_name()));
+			return;
+		}
+	} else {
+		// We are dealing with an Array.
+		// Let's check if the subtype of the array matches first.
+		// This is needed because the set method of ScriptInstance checks for type,
+		// but the ClassDB set method doesn't! So we cannot reliably know what actually happens.
+		Array current_array = current;
+		Array placeholder_array = p_set.value;
+		if (current_array.is_same_typed(placeholder_array)) {
+			p_instance->set(p_set.name, p_set.value, &is_valid);
+			if (is_valid) {
+				return;
+			}
+			// Internal array types match but setting failed? This is strange, so let's print a warning!
+			WARN_PRINT(vformat("Array Property '%s' with type '%s' could not be set when creating instance of '%s'.", p_set.name, Variant::get_type_name(Variant::Type(current_array.get_typed_builtin())), p_placeholder->get_name()));
+		}
+		// Arrays are not the same internal type. This should be happening because we have a NodePath Array,
+		// but the instance wants a Node Array.
+	}
+
+	switch (current_type) {
+		case Variant::Type::NIL:
+			if (placeholder_type != Variant::Type::NODE_PATH) {
+				break;
+			}
+			// If it's nil but we have a NodePath, we guess what works.
+
+			p_instance->set(p_set.name, p_set.value, &is_valid);
+			if (is_valid) {
+				break;
+			}
+
+			p_instance->set(p_set.name, try_get_node(p_placeholder, p_instance, p_set.value), &is_valid);
+			break;
+		case Variant::Type::OBJECT:
+			if (placeholder_type != Variant::Type::NODE_PATH) {
+				break;
+			}
+			// Easiest case, we want a node, but we have a deferred NodePath.
+			p_instance->set(p_set.name, try_get_node(p_placeholder, p_instance, p_set.value));
+			break;
+		case Variant::Type::ARRAY: {
+			// If we have reached here it means our array types don't match,
+			// so we will convert the placeholder array into the correct type
+			// and resolve nodes if necessary.
+			Array current_array = current;
+			Array converted_array;
+			Array placeholder_array = p_set.value;
+			converted_array = current_array.duplicate();
+			converted_array.resize(placeholder_array.size());
+
+			if (Variant::evaluate(Variant::OP_EQUAL, current_array.get_typed_builtin(), Variant::Type::NODE_PATH)) {
+				// We want a typed NodePath array.
+				for (int i = 0; i < placeholder_array.size(); i++) {
+					converted_array.set(i, placeholder_array[i]);
+				}
+			} else {
+				// We want Nodes, convert NodePaths.
+				for (int i = 0; i < placeholder_array.size(); i++) {
+					converted_array.set(i, try_get_node(p_placeholder, p_instance, placeholder_array[i]));
+				}
+			}
+
+			p_instance->set(p_set.name, converted_array, &is_valid);
+			if (!is_valid) {
+				WARN_PRINT(vformat("Property '%s' with type '%s' could not be set when creating instance of '%s'.", p_set.name, Variant::get_type_name(current_type), p_placeholder->get_name()));
+			}
+			break;
+		}
+		default:
+			WARN_PRINT(vformat("Property '%s' with type '%s' could not be set when creating instance of '%s'.", p_set.name, Variant::get_type_name(current_type), p_placeholder->get_name()));
+			break;
+	}
+}
+
+Node *InstancePlaceholder::try_get_node(InstancePlaceholder *p_placeholder, Node *p_instance, const NodePath &p_path) {
+	// First try to resolve internally,
+	// if that fails try resolving externally.
+	Node *node = p_instance->get_node_or_null(p_path);
+	if (node == nullptr) {
+		node = p_placeholder->get_node_or_null(p_path);
+	}
+
+	return node;
 }
 
 Dictionary InstancePlaceholder::get_stored_values(bool p_with_order) {