Main loop scripts can use but not statically reference autoloads

[mihe]

Tested versions

• Reproducible in: 4.6.dev [16a11ac]

System information

Godot v4.6.dev (16a11ac) - Fedora Linux 42 (Adams) on Wayland - X11 display driver, Multi-window, 2 monitors - Vulkan (Forward+) - dedicated AMD Radeon RX 9070 XT (RADV GFX1201) - AMD Ryzen 9 9950X3D 16-Core Processor (32 threads) - 60.39 GiB memory

Issue description

When using a custom main loop script through the application/run/main_loop_type project setting, where the script is written in GDScript, and you try to reference an autoload global statically through GDScript from something like its _initialize method, like so:

class_name MyMainLoop
extends SceneTree

func _initialize() -> void:
    MyAutoload.greet()

... you end up with parser errors saying:

Parser Error: Identifier not found: MyAutoload

However, the autoloads are in fact set up by that point, meaning you can do something like this from a main loop script that derives from SceneTree:

class_name MyMainLoop
extends SceneTree

func _initialize() -> void:
    root.get_node("MyAutoload").call("greet")

The reason for this seems to be that the main loop script is instantiated before the autoloads are set up and registered, but its _initialize method is called after the autoloads are set up.

Is this just how it has to be perhaps? Is there a good reason for why the main loop is instantiated long before its _initialize method is called?

Steps to reproduce

1. Open the MRP
2. Run the main scene
3. Note the parser error
4. Go into my_main_loop.gd
5. Comment out MyAutoload.greet()
6. Uncomment root.get_node("MyAutoload").call("greet")
7. Run the main scene again
8. Note how the code runs fine

Minimal reproduction project (MRP)

main-loop-using-autoload.zip

[ydeltastar]

My PR #110295, which reorders the autoload registration logic to fix script usage via the command line, appears to fix this use case too.