How to detect hot reload without const mutation?

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1

Godot Version

4.4.1

Question

I’m looking for a method to notify my class when a hot reload occurs. I read this thread, where two solutions were suggested.

  1. Modify a const dictionary - since const is reloaded every hot reload, you can detect it easily.
  2. Compare with get_script().source_code and see if something changed.

I tried solution 1, but I have build errors indicating the dictionary is (correctly) read-only. Perhaps that solution worked in the past, but not on the latest Godot version.

For solution 2, get_script() only fetches the current class, but my modifications are in an extending class, so it doesn’t quite work either.

Any suggestions?

2

Perhaps a global script with a build number? I’m spitballing here, not sure if this would work:

# Totally untested...

extends Node

var build_number:        int = 0
var cached_build_number: int = 1 # Ignore the first load...

signal reloaded

func _ready() -> void:
    build_number += 1

func _process(_delta: float) -> void:
    if cached_build_number < build_number:
        cached_build_number = build_number
        print("We have rebuilt it, stronger.  We had the technology.")
        reloaded.emit()

The logic here is that build_number and cached_build_number should retain their values through a hot reload (I think?), but the reload will call _ready() and increment build_number.

Edit: Actually, thinking about it, it could be simplified…

# Totally untested...

extends Node

var build_number:        int = 0
var cached_build_number: int = 1 # Ignore the first load...

signal reloaded

func _ready() -> void:
    build_number += 1
    if cached_build_number < build_number:
        cached_build_number = build_number
        print("We have rebuilt it, stronger.  We had the technology.")
        reloaded.emit()
3

This approach relies on hot reload calling _ready, which it does not. In fact, hot reload is eerily quiet, calling no lifecycle methods nor emitting any notifications.