Add ClassDB::has_instance_binding_callbacks() and check before getting callbacks in internal::get_object_instance_binding()

[Daylily-Zeleen]

In my case, I need to get all singletons from Engine::get_singleton()->get_singleton(), but if it has not instance callbacks, it will print a error and return a invalid object.
I add ClassDB::has_instance_binding_callbacks() to check if it is available or not.

I think this is beneficial to do some reflection operations like in C#, so I open this pr.

[dsnopek]

Thanks!

Can you give some more details about the behavior you're getting from Engine::get_singleton()->get_singleton()? Which singletons have this problem and why don't they have instance callbacks? Are the instance callbacks unavailable because you're trying to get it too early, before the class has been registered?

but if it has not instance callbacks, it will print a error and return a invalid object

In what way is it invalid?

I'd really love for Engine::get_singleton()->get_singleton() to always return either nullptr or a valid object, so if there's conditions where it isn't, I think that should probably be fixed, rather than adding ClassDB::has_instance_binding_callbacks().

[Daylily-Zeleen]

Oh, my mistake, it will print an error but return a valid Object *.
Only occur when get ClassDB and GDScriptLanguageProtocol, these two classes are not generated binding callbacks currently.
Here is my test code:

void initialize_example_module(ModuleInitializationLevel p_level) {
	if (p_level != MODULE_INITIALIZATION_LEVEL_SCENE) {
		return;
	}

	PackedStringArray singleton_names = Engine::get_singleton()->get_singleton_list();
	for (const String &singleton_name : singleton_names) {
		Object *singleton = Engine::get_singleton()->get_singleton(singleton_name);
		bool valid = singleton != nullptr;
		bool has_instance_binding_callbacks = ClassDB::has_instance_binding_callbacks(singleton_name);
		if (!valid || !has_instance_binding_callbacks) {
			UtilityFunctions::print_verbose(vformat("Singleton \"%s\" is invalid? %s, has instance binding? %s.", singleton_name, valid, has_instance_binding_callbacks));
		} else {
			UtilityFunctions::print(vformat("Get singleton \"%s\" is success.", singleton_name));
		}
	}
}

In src/core/object.cpp, line 53.
Maybe we should do some check here before Class::get_instance_binding_callbacks()(at line 54) to avoid that print a error message in Class::get_instance_binding_callbacks(), the added method Class::has_instance_binding_callbacks() still useful.

[Daylily-Zeleen]

@dsnopek By the way, if I want to be a author in "AUTHORS.md", should I have be merged at least 11 commits only in godot repo? Or my commits in this repo will be counted, too?

[dsnopek]

By the way, if I want to be a author in "AUTHORS.md", should I have be merged at least 11 commits only in godot repo? Or my commits in this repo will be counted, too?

I just asked internally and only commits to the main Godot repo are counted. However, you've made some really great GDExtension contributions, both to Godot and godot-cpp - Thank You So Much! I think you'll get there eventually :-)

[Daylily-Zeleen]

Thanks for your reply!

[dsnopek]

Oh, my mistake, it will print an error but return a valid Object *.
Only occur when get ClassDB and GDScriptLanguageProtocol, these two classes are not generated binding callbacks currently.

Ah, ok, thanks for the clarification!

Maybe we should do some check here before Class::get_instance_binding_callbacks()(at line 54) to avoid that print a error message in Class::get_instance_binding_callbacks()

Hm, I'm not sure that's what we want to do. There may be classes added to Godot after the creation of the GDExtension, which won't be listed in the instance bindings. In that case, we probably do want an Object * (or whatever is the closest parent class that we do have bindings for) so that the object can still be used somewhat.

See #1165

[Daylily-Zeleen]

Issue is fixed by #1165.