Script not finding child node in setget method

[deleted]

I have a scene with this structure:

root
    child

The root node has a script with a setter var:

extends Node2D

export(Color) var colour = Color(1, 1, 1) setget _set_colour

func _set_colour(new_val):
    colour = new_val
    # Other relevant logic
    ...
    get_node("child").set_modulate(new_val)
    ...

When I instance this scene in another it fails to load when running the project because _set_colour runs but get_node("child") returns null.

I've attached a minimal project so you can see what I'm trying to do and what's happening.

[deleted]

I asked this in Godot Q&A and the answer was to add a null check and do an initial update to the child in _ready.

extends Node2D

export(Color) var colour = Color(1, 1, 1) setget _set_colour

func _ready():
    _update_child()

func _set_colour(new_val):
    colour = new_val
    ...
    _update_child()

func _update_child():
    if has_child("child"):
        get_node("child").set_modulate(colour)

I was initially skeptical of this approach because my script is actually a tool script, and I was worried I wouldn't actually see the changes made to child in the editor if I did it this way. But it turns out that the changes are visible in the editor.