Add reference @export properties

[Furgl]

Context

I'm creating a GameState system where each GameState is a custom resource. I would like each GameState to know which Scene to load when it becomes active and to also know which other GameState to switch to when the escape key is pressed.

Example code:

class_name GameState extends Resource

@export var scene: PackedScene
@export var escape_state: GameState

The Problem

1. Resources that are properties of a resource seem to be auto-loaded when that resource is loaded
In this case, scene is auto-loaded when the GameState is loaded. This is not ideal because I want all of the GameStates to be loaded, but only the currently active GameState's scene to be loaded.

2. Resource properties cannot create circular references
During gameplay, I want pressing escape to open a pause menu. Then pressing escape again should close the pause menu and return to gameplay.
To do that, I would create two GameStates:

• A Gameplay GameState with escape_state set to a Pause_Menu GameState
• A Pause_Menu GameState with escape_state set to the Gameplay GameState

This cannot be done and causes this error to appear:

Recursion detected, unable to assign resource to property.

Possible Solution

An @export_ref annotation for a String property that stores the path of the resource, but the benefit would be that the path updates if the resource is moved or renamed to allow for easy refactoring. At runtime, the resource can be loaded from the path as needed.

Alternatives

scene and escape_state could be changed to String and set to the paths of their resources, but that would not support moving or renaming resources and would make refactoring difficult.

[pixel-boy]

I wonder if UIDs will make this easier to do, maybe it's something planned?

In any case the current limitation has often bothered me, and it would be nice to have an automatic update of the exported file paths.

[jitspoe]

Should this be a discussion or an issue? I'm also running into an issue with resources being referenced and loaded as a resource, but with importer settings. Storing a reference to a resource inside of the default preset for an importer causes the whole project to fail to load: godotengine/godot#83316

Other related issues:
godotengine/godot#99267
#8350