🔥 Hot reloading

[bitbrain]

While debugging my game, I want to change things in Pandora and see them reflected in my game instantly. Currently, you have to restart the game in order for changes to take effect.

[JohnC0de]

Hi @bitbrain 👋

I'd like to help implement hot-reloading for Pandora and have put together a small prototype to start the conversation.

Proposed approach

1. File watcher node (file_watcher.gd)

   @tool
   class_name PandoraFileWatcher
   extends Node
   
   signal file_changed(file_path: String)
   
   var _watched_file: String
   var _last_modified_time: int = 0
   var _check_timer := Timer.new()
   var _debounce_timer := Timer.new()
   
   func _ready() -> void:
       _check_timer.wait_time = 0.5
       _check_timer.autostart = true
       _check_timer.timeout.connect(_check_file_changes)
       add_child(_check_timer)
   
       _debounce_timer.wait_time = 0.2
       _debounce_timer.one_shot = true
       _debounce_timer.timeout.connect(_emit_file_changed)
       add_child(_debounce_timer)
   
   func watch_file(file_path: String) -> void:
       _watched_file = file_path
       if FileAccess.file_exists(_watched_file):
           _last_modified_time = FileAccess.get_modified_time(_watched_file)
   
   func _check_file_changes() -> void:
       if _watched_file.is_empty() or not FileAccess.file_exists(_watched_file):
           return
       var current_time = FileAccess.get_modified_time(_watched_file)
       if current_time > _last_modified_time:
           _last_modified_time = current_time
           _debounce_timer.start()
   
   func _emit_file_changed() -> void:
       file_changed.emit(_watched_file)
   

2. Integrate in api.gd

   signal data_reloaded
   
   var _file_watcher := PandoraFileWatcher.new()
   add_child(_file_watcher)
   _file_watcher.file_changed.connect(_on_data_file_changed)
   _file_watcher.watch_file(data_path)
   
   func _on_data_file_changed(_fp: String) -> void:
       reload_data()
   
   func reload_data() -> void:
       if not _loaded:
           return
       _clear()
       load_data()
       data_reloaded.emit()
   

Questions & next steps

• Scope – Is watching a single data file enough for the first iteration, or do we also want to monitor entire folders / other asset types?
• Performance – A 0.5s polling interval feels responsive in practice, but I can expose it as an export var if you'd prefer configurability.
• Debounce – I added a 0.2s debounce to avoid double-fires on rapid saves; let me know if that should be tuned differently.
• API surface – Are the file_changed and data_reloaded signals the hooks you had in mind, or would you like a different design?

If this direction looks good I'm happy to polish it and open a PR.

Thanks, and let me know what you think!

[bitbrain]

Feel free to create a PR and I can leave specific feedback on the code itself. This is a great start!

One issue I can see is object referencing: after reloading the data, objects in the game may still have their old objects initialized, so the new state is not reflected in-game. To make matters more complex, there are also "entity instances" that should automatically receive those changes.