Modifying a static variable in a extended script modifies the parent script static variable instead

[TheMegax]

Tested versions

• Reproducible since 4.1-dev2

System information

Godot v4.3.dev2 - Windows 10.0.22621 - Vulkan (Forward+) - dedicated NVIDIA GeForce GTX 1650 SUPER (NVIDIA; 31.0.15.4617) - Intel(R) Core(TM) i5-9400F CPU @ 2.90GHz (6 Threads)

Issue description

The way static variables are handled in GDScript differ from other programming languages, where they're not inherited to children GDScript classes. Instead, the parent class controls the static variables of all children.

Steps to reproduce

The MRP has the following structure:

Parent.gd

class_name Parent
extends Node

static var PROPERTY_1 : int
static var PROPERTY_2 : String

Child1.gd

class_name Child1
extends Parent

static func _static_init():
	PROPERTY_1 = 10
	PROPERTY_2 = "Child1"

Child2.gd

class_name Child2
extends Parent

static func _static_init():
	PROPERTY_1 = 5
	PROPERTY_2 = "Child2"

Main.gd

extends Node2D

func _ready():
	print(Child1.PROPERTY_1)
	print(Child1.PROPERTY_2)
	
	print(Child2.PROPERTY_1)
	print(Child2.PROPERTY_2)

Main.gd is included in the main scene.
The assumption goes that the result in the console would look like this

10
Child1
5
Child2

But instead it prints the following.

5
Child2
5
Child2

Minimal reproduction project (MRP)

MRP.zip

[dalexeev]

This is documented:

A base class static variable can also be accessed via a child class:

class A:
    static var x = 1

class B extends A:
    pass

func _ready():
    prints(A.x, B.x) # 1 1
    A.x = 2
    prints(A.x, B.x) # 2 2
    B.x = 3
    prints(A.x, B.x) # 3 3 

A static variable belongs to the class in which it is defined. Child classes do not inherit static variables as independent copies, you simply get the ability to reference ancestor static variables in the child class. For example, PHP has the same behavior.