C#: Get singleton instances using the Core name

[RedworkDE]

• Followup to C#: Check if a class is a singleton using the Core name #73882
• Fixes Using ResourceUid in C# gives error #74270

[raulsntos]

Shouldn't it be itype.name like we use in the static NativeName field?

Suggested change

	<< itype.cname
	<< itype.name

[RedworkDE]

I am actually not sure whats the difference between those two, beyond that one is a String and the other a StringName I picked cname because you used type_cname in your PR and that was the closest thing available here and it gave the correct result.

[RedworkDE]

As far as I can tell they come from https://github.com/godotengine/godot/blob/6ce1d89842ad400a640bedc692ec07bfb59bca6b/modules/mono/editor/bindings_generator.h#L543-L550 and I coudn't find any instance where they are set to different values.

[raulsntos]

I think they are the same, probably to avoid converting between String and StringName multiple times.

In my PR, the Engine::has_singleton method takes a StringName so I used cname. In this case, since the << operator takes a String it may be better to use name and avoid the conversion.

Actually, wait, they may not always be the same.

and I coudn't find any instance where they are set to different values.

🤔 I think I've seen some cases where they aren't. Maybe for the generated classes they happen to coincidentally always be the same.

[RedworkDE]

Well, I tried both and they generate the exact same code, so I switched to avoid the unnecessary conversion and keep it in sync with the NativeName.

[raulsntos]

LGTM, but @neikeq may want to chime in about the difference between itype.name and itype.cname because I'm also a bit confused by it. We should probably add comments documenting them.

[neikeq]

Now that this is using the native name, it would be more appropriate to use the NativeName field and update godotsharp_engine_get_singleton to use StringName. But we can't do the latter without breaking compat (we could add a new native call, but it's not worth for this), so it will have to be in Godot 5.

itype.name and itype.cname are the same, but the former is a String and the latter StringName.

[akien-mga]

Thanks!

[YuriSizov]

Cherry-picked for 4.0.1.