C#: Area3D node error calling from signal "input_event" - Method not found

[BrandonGillis]

Godot version

v4.0.beta2.mono.official [f8745f2]

System information

Windows 11 x64

Issue description

I made a simple 3D Scene with an Area3D node to detect mouse movement with a CollisionShape3D.
When registering the input_event signal inside a C# script and I hover my mouse over the CollisionShape it try to fire the input_event signal but doesn't find the method associated to it and spam this error :

E 0:00:00:0910   emit_signalp: Error calling from signal 'input_event' to callable: 'Area3D(Area3d.cs)::_on_area_3d_input_event': Method not found..
  <Source C++>   core/object/object.cpp:1057 @ emit_signalp()

Steps to reproduce

1. Download the minimal reproduction project below
2. There's one C# script on the Area3D node with the input_event signal binded to it with the following code :

using Godot;
using System;

public partial class Area3d : Area3D
{
	private void _on_area_3d_input_event(object camera, object @event, Vector3 position, Vector3 normal, int shape_idx)
	{
		GD.Print("collision event");
	}
}

3. Run the game and move your mouse inside the game.
4. You should be spammed inside the debugger with this error :
   

Minimal reproduction project

Area3DInputEventBug.zip

[akien-mga]

CC @godotengine/dotnet

Didn't check but a potential cause of this error is if the callback parameters don't properly match what is expected by the signal. I don't know if object is valid here or if it should be further specified.

If this is the problem, we really need to improve the error message to point out when the method name is correct but the signature isn't.

[BrandonGillis]

To add some details the signature of the current method is the one generated automatically from the Godot editor

[raulsntos]

Signals currently only support 64-bit types so the int parameter should be long. The object parameter also looks weird because we no longer support System.Object it likely should be Godot.Variant.

[BrandonGillis]

I confirm that updating the method signature to the following fix the method not found error :

	private void _on_area_3d_input_event(Variant camera, Variant @event, Vector3 position, Vector3 normal, long shape_idx)
	{
		GD.Print("collision event");
	}

Strong typing also works good :

private void _on_area_3d_input_event(Camera3D camera, InputEvent @event, Vector3 position, Vector3 normal, int shape_idx)

Keeping an int for the shape_idx make it work too :

private void _on_area_3d_input_event(Variant camera, Variant @event, Vector3 position, Vector3 normal, int shape_idx)

Things to improve :

• Error message as @akien-mga suggested, this is not really a method not found but a signature issue.
• int type in the signature should trigger an error ?
• The generated signature from Godot Editor when connecting a signal

[raulsntos]

We used System.Object (now Godot.Variant) when we don't know or can't figure out what the type is, in this case it seems we should be able to provide more concrete types though from the core API.

For the int parameter, it likely works in this case because internally the signal is emitted using an int but in other cases it may not so we have to assume it's a long unless otherwise specified and the core API right now doesn't specify this for signals or virtual methods (see godotengine/godot-proposals#5403 (comment)).

[BrandonGillis]

Should we split the method not found into another issue or is it ok to keep it in this one?

I would like to try fixing that one if it's ok, as I think it would be a nice candidate for a first contribution

[raulsntos]

There is an open issue we can use to keep track of that: #35910

I don't think it would be an easy fix for a first contribution, it likely requires changing Godot.Object.InvokeGodotClassMethod to be able to return godot_variant_call_error and then modify the ScriptMethodsGenerator appropriately but I don't know if that change would be desired since making it return a boolean was likely intentional.