Loading GDExtensions fails on first run when .godot/extension_list.cfg is not generated yet

[akien-mga]

Godot version

4.0.dev (4735a03)

System information

Linux, Mageia 9 x86_64

Issue description

When running a project using a GDExtension while the .godot/extension_list.cfg file doesn't exist yet, or hasn't been updated for a new extension, the editor will throw errors, such as:

SCRIPT ERROR: Parse Error: "Example" was not found in the current scope.
          at: GDScript::reload (res://main.gd:9)
ERROR: Method/function failed. Returning: ERR_PARSE_ERROR
   at: reload (modules/gdscript/gdscript.cpp:855)
ERROR: Condition "p_level <= int32_t(level_initialized)" is true.
   at: initialize_library (core/extension/native_extension.cpp:299)
SCRIPT ERROR: Parse Error: "Example" was not found in the current scope.
          at: GDScript::reload (res://main.gd:9)
ERROR: Method/function failed. Returning: ERR_PARSE_ERROR
   at: reload (modules/gdscript/gdscript.cpp:855)
ERROR: Cannot get class 'Example'.
   at: is_class_enabled (core/object/class_db.cpp:1538)
WARNING: Node Example of type Example cannot be created. A placeholder will be created instead.
     at: instantiate (scene/resources/packed_scene.cpp:164)
ERROR: In Object of type 'Node': Attempt to connect nonexistent signal 'custom_signal' to callable 'Node(main.gd)::_on_Example_custom_signal'.
   at: connect (core/object/object.cpp:1328)

Then the .godot/extension_list.cfg is properly generated and used successfully on subsequent edits, but this first use bug is annoying.

Steps to reproduce

• Build godot-cpp example following instructions in https://godotengine.org/article/introducing-gd-extensions
• Run it (delete .godot or .godot/extension_list.cfg if it exists to reproduce the bug)

Minimal reproduction project

https://github.com/godotengine/godot-cpp/tree/master/test/demo

[mhilbrunner]

Note: mkdir .godot and copying the extension_list.cfg in there before the first open seems to work as a workaround without any adverse effects, which is useful to get this to build on CI.

Still an annoying issue. :)

The code seems to be aware of the issue:

godot/editor/editor_file_system.cpp

Lines 613 to 624 in 780f5c0

	if (_scan_extensions()) {
	//needs editor restart
	//extensions also may provide filetypes to be imported, so they must run before importing
	if (EditorNode::immediate_confirmation_dialog(TTR("Some extensions need the editor to restart to take effect."), first_scan ? TTR("Restart") : TTR("Save&Restart"), TTR("Continue"))) {
	if (!first_scan) {
	EditorNode::get_singleton()->save_all_scenes();
	}
	EditorNode::get_singleton()->restart_editor();
	//do not import
	return true;
	}
	}

However, I could not get this popup to trigger in my testing. This also seems quite hacky.

What I figure may be happening is that in the editor's file system scanning, code files are scanned first (which leads to the editor trying to compile them), and that then errors if the extensions are missing because thes code is referencing them and thus stuff that's not (yet) available.

Maybe we can make sure extensions are loaded and initialized before any other imports or the first editor file system scan.

[mhilbrunner]

By BastiaanOlij on RC:

At startup godot only loads what is added to the gdextension config file in your .import folder and the first time your library isn’t there.
Than later on the editor will scan for new extensions and add them, it does this everytime godot gets focus i think. At this time loading of the extension fails because there is a failsafe to ensure class types are loaded in order, and the order is set to the last type when extensions were originally processed.
Not sure what to do about it though

[BastiaanOlij]

Ah yes, the folder is now called .godot and the file I was thinking about is extension_list.cfg. I was typing that on my phone so was remembering the old names :)

I see two potential options here:

1. perform the initial scan for new extensions right after we load the extension_list.cfg when using the editor build, so something like:

load_extension_list()
#ifdef TOOLS_ENABLED
    scan_extensions()
#endif

2. remove the failsafe so libraries don't fail when loaded after the editor is already loaded, I really don't get its purpose to be honest and it will allow you to copy extension into your new project and have them load right away.

[YuriSizov]

Is this still an issue? @akien-mga @BastiaanOlij @dsnopek

[dsnopek]

I've never personally encountered this issue.

I just tried to reproduce it by deleting the .godot/extension_list.cfg file in a project that uses a GDExtension, and then opening it in the editor. Everything appeared to load up fine, including the default scene which used nodes from the GDExtension. Looking on the console I didn't see any unexpected errors.

So, unless I'm missing a reproduction step, I think it's not an issue anymore?