Universalize UID support in all resource types

Ensures all resource types support UIDs in a project.

This is required to fix:
* Scripts and many other resource types can't be referenced by UID and when refactored the references are lost.
* Path export properties can't use UID for unsupported types.
* Refactoring problems when files are moved outside the editor (this PR effectively fixes it).
* Editor properly refreshing paths if they changed externally while opened (as example, git update).
  This needs to be addressed in a subsequent PR, but this one effectively sets the prerequisites.

Resource types that do not support UID will get a .uid file appended to them (this includes .gd, .gdshader, .gdextension, etc. files).

core/io/resource_format_binary.cpp

@@ -1577,6 +1577,10 @@ ResourceUID::ID ResourceFormatLoaderBinary::get_resource_uid(const String &p_pat
 	return loader.uid;
 }
 
+bool ResourceFormatLoaderBinary::has_custom_uid_support() const {
+	return true;
+}
+
 ///////////////////////////////////////////////////////////
 ///////////////////////////////////////////////////////////
 ///////////////////////////////////////////////////////////

core/io/resource_format_binary.h

@@ -118,6 +118,7 @@ public:
 	virtual String get_resource_script_class(const String &p_path) const override;
 	virtual void get_classes_used(const String &p_path, HashSet<StringName> *r_classes) override;
 	virtual ResourceUID::ID get_resource_uid(const String &p_path) const override;
+	virtual bool has_custom_uid_support() const override;
 	virtual void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false) override;
 	virtual Error rename_dependencies(const String &p_path, const HashMap<String, String> &p_map) override;
 };

core/io/resource_importer.cpp

@@ -387,6 +387,10 @@ ResourceUID::ID ResourceFormatImporter::get_resource_uid(const String &p_path) c
 	return pat.uid;
 }
 
+bool ResourceFormatImporter::has_custom_uid_support() const {
+	return true;
+}
+
 Error ResourceFormatImporter::get_resource_import_info(const String &p_path, StringName &r_type, ResourceUID::ID &r_uid, String &r_import_group_file) const {
 	PathAndType pat;
 	Error err = _get_path_and_type(p_path, pat);

core/io/resource_importer.h

@@ -70,6 +70,7 @@ public:
 	virtual bool handles_type(const String &p_type) const override;
 	virtual String get_resource_type(const String &p_path) const override;
 	virtual ResourceUID::ID get_resource_uid(const String &p_path) const override;
+	virtual bool has_custom_uid_support() const override;
 	virtual Variant get_resource_metadata(const String &p_path) const;
 	virtual bool is_import_valid(const String &p_path) const override;
 	virtual void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false) override;

core/io/resource_loader.cpp

@@ -112,10 +112,21 @@ String ResourceFormatLoader::get_resource_script_class(const String &p_path) con
 
 ResourceUID::ID ResourceFormatLoader::get_resource_uid(const String &p_path) const {
 	int64_t uid = ResourceUID::INVALID_ID;
-	GDVIRTUAL_CALL(_get_resource_uid, p_path, uid);
+	if (has_custom_uid_support()) {
+		GDVIRTUAL_CALL(_get_resource_uid, p_path, uid);
+	} else {
+		Ref<FileAccess> file = FileAccess::open(p_path + ".uid", FileAccess::READ);
+		if (file.is_valid()) {
+			uid = ResourceUID::get_singleton()->text_to_id(file->get_line());
+		}
+	}
 	return uid;
 }
 
+bool ResourceFormatLoader::has_custom_uid_support() const {
+	return GDVIRTUAL_IS_OVERRIDDEN(_get_resource_uid);
+}
+
 void ResourceFormatLoader::get_recognized_extensions_for_type(const String &p_type, List<String> *p_extensions) const {
 	if (p_type.is_empty() || handles_type(p_type)) {
 		get_recognized_extensions(p_extensions);
@@ -1159,6 +1170,21 @@ ResourceUID::ID ResourceLoader::get_resource_uid(const String &p_path) {
 	return ResourceUID::INVALID_ID;
 }
 
+bool ResourceLoader::has_custom_uid_support(const String &p_path) {
+	String local_path = _validate_local_path(p_path);
+
+	for (int i = 0; i < loader_count; i++) {
+		if (!loader[i]->recognize_path(local_path)) {
+			continue;
+		}
+		if (loader[i]->has_custom_uid_support()) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
 String ResourceLoader::_path_remap(const String &p_path, bool *r_translation_remapped) {
 	String new_path = p_path;
 

core/io/resource_loader.h

@@ -81,6 +81,7 @@ public:
 	virtual String get_resource_type(const String &p_path) const;
 	virtual String get_resource_script_class(const String &p_path) const;
 	virtual ResourceUID::ID get_resource_uid(const String &p_path) const;
+	virtual bool has_custom_uid_support() const;
 	virtual void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false);
 	virtual Error rename_dependencies(const String &p_path, const HashMap<String, String> &p_map);
 	virtual bool is_import_valid(const String &p_path) const { return true; }
@@ -238,6 +239,7 @@ public:
 	static String get_resource_type(const String &p_path);
 	static String get_resource_script_class(const String &p_path);
 	static ResourceUID::ID get_resource_uid(const String &p_path);
+	static bool has_custom_uid_support(const String &p_path);
 	static void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false);
 	static Error rename_dependencies(const String &p_path, const HashMap<String, String> &p_map);
 	static bool is_import_valid(const String &p_path);

doc/classes/ResourceFormatLoader.xml

@@ -57,6 +57,7 @@
 			<return type="int" />
 			<param index="0" name="path" type="String" />
 			<description>
+				Should return the unique ID for the resource associated with the given path. If this method is not overridden, a [code].uid[/code] file is generated along with the resource file, containing the unique ID.
 			</description>
 		</method>
 		<method name="_handles_type" qualifiers="virtual const">

editor/editor_file_system.cpp

@@ -1259,6 +1259,15 @@ void EditorFileSystem::_process_file_system(const ScannedDirectory *p_scan_dir,
 					}
 				}
 			}
+
+			if (fi->uid == ResourceUID::INVALID_ID && ResourceLoader::exists(path) && !ResourceLoader::has_custom_uid_support(path) && !FileAccess::exists(path + ".uid")) {
+				// Create a UID.
+				Ref<FileAccess> f = FileAccess::open(path + ".uid", FileAccess::WRITE);
+				if (f.is_valid()) {
+					fi->uid = ResourceUID::get_singleton()->create_id();
+					f->store_line(ResourceUID::get_singleton()->id_to_text(fi->uid));
+				}
+			}
 		}
 
 		if (fi->uid != ResourceUID::INVALID_ID) {

editor/filesystem_dock.cpp

@@ -1446,6 +1446,13 @@ void FileSystemDock::_try_move_item(const FileOrFolder &p_item, const String &p_
 			}
 		}
 
+		if (p_item.is_file && FileAccess::exists(old_path + ".uid")) {
+			err = da->rename(old_path + ".uid", new_path + ".uid");
+			if (err != OK) {
+				EditorNode::get_singleton()->add_io_error(TTR("Error moving:") + "\n" + old_path + ".uid\n");
+			}
+		}
+
 		// Update scene if it is open.
 		for (int i = 0; i < file_changed_paths.size(); ++i) {
 			String new_item_path = p_item.is_file ? new_path : file_changed_paths[i].replace_first(old_path, new_path);

scene/resources/resource_format_text.cpp

@@ -1526,6 +1526,10 @@ ResourceUID::ID ResourceFormatLoaderText::get_resource_uid(const String &p_path)
 	return loader.get_uid(f);
 }
 
+bool ResourceFormatLoaderText::has_custom_uid_support() const {
+	return true;
+}
+
 void ResourceFormatLoaderText::get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types) {
 	Ref<FileAccess> f = FileAccess::open(p_path, FileAccess::READ);
 	if (f.is_null()) {

scene/resources/resource_format_text.h

@@ -155,6 +155,7 @@ public:
 	virtual String get_resource_type(const String &p_path) const override;
 	virtual String get_resource_script_class(const String &p_path) const override;
 	virtual ResourceUID::ID get_resource_uid(const String &p_path) const override;
+	virtual bool has_custom_uid_support() const override;
 	virtual void get_dependencies(const String &p_path, List<String> *p_dependencies, bool p_add_types = false) override;
 	virtual Error rename_dependencies(const String &p_path, const HashMap<String, String> &p_map) override;