Errors from godot registration functions are not detected

[0x53A]

I stumbled upon this here: https://github.com/godot-rust/gdext/pull/1019#issuecomment-2603887272

See also: https://github.com/godotengine/godot/issues/101870

The issue is that in godot, classdb_register_extension_class_method returns void.

If an error occurs, it just prints an error and returns:

https://github.com/godotengine/godot/blob/1b7b009674e05b566be11a5377b935f5d3d6c0ee/core/object/class_db.cpp#L1879-L1882

	if (type->method_map.has(p_method->get_name())) {
		// overloading not supported
		ERR_FAIL_MSG(vformat("Method already bound '%s::%s'.", p_class, p_method->get_name()));
	}

The macro ERR_FAIL_MSG ultimately calls _err_print_error

which prints to stderr and calls all handlers registered in error_handler_list.

At the least for debug / CI, it would be great to register a handler, and fail CI if an error occurs.

[0x53A]

Note: godot seems to do something similar here: https://github.com/godotengine/godot/blob/1b7b009674e05b566be11a5377b935f5d3d6c0ee/tests/test_tools.h#L39

[0x53A]

My Rust <-> Cpp interop knowledge is limited, but I believe we can't just call that function, without it being explicitly exposed, right? I added a feature request here: https://github.com/godotengine/godot-proposals/issues/11618

[Bromeon]

You're right, the only way to interact with Godot is through gdextension_interface.h. We additionally have extension_api.json, but this contains just data, no functions.

And indeed, classdb_register_extension_class_method does not return a status code, and I'm not aware of an API to fetch previous errors, either.

An alternative to having errors on Godot side would be:

• validate invariants (symbol not yet registered) beforehand, through ClassDB API
• maintain runtime state on godot-rust side and check against that

Both work for simple cases, but may fall apart for more complex validations, and would require Rust to keep up with the exact logic that Godot provides.