GDScriptNativeClass reported as Object but missing methods in GDScript

[kumikumi]

Godot version

4.0.2

System information

• OS: Ubuntu 22.04
• Godot version: 4.0.2

Issue description

The type GDScriptNativeClass is not exposed to GDScript, but a value of such type can be obtained during runtime.

The value seems indistinquishable from a valid Object and appears to have a "get_method_list" function, but trying to call it results in a crash.

I believe the value is Object check in the attached code should either evaluate to false, or the value should have the methods that Objects have according to the docs.

Edit: Turns out that it works if you cast it to Object first (see code example)

Steps to reproduce

func inspect_variant(value: Variant):
	print(value) # <GDScriptNativeClass#-9223372028063514189>
	print("Is object: ", value is Object) # Is object: true
	print("Is valid: ", is_instance_valid(value)) # Is valid: true
	print("Has get_method_list: ", "get_method_list" in value) # Has get_method_list: true
	print(value.get_method_list) # GDScriptNativeClass::get_method_list
	print(value["get_method_list"]) # GDScriptNativeClass::get_method_list
	#print("method list: ", value.get_method_list()) # Invalid call. Nonexistent function 'get_method_list' in base 'Button'
	print("method list: ", (value as Object).get_method_list()) # Works!

func _init():
	var foo = Button
	inspect_variant(foo)

Minimal reproduction project

N/A

[AThousandShips]

How did you obtain a reference to one? That's kinda relevant here

The reason this happens is because it overrides the callp function and blocks non-static calls

[AThousandShips]

It looks like you're just taking the static type here, so obviously there should be no non-static access, the error message should be clearer though

Your code is equivalent to Button.get_method_list()

Related to #66675, and is intended behaviour, see #72286

See also #71978

[kumikumi]

Note that in this case the value has at least one method: .new() that I'm able to call on it. Ideally there would be a way to list the available methods.

At the very least, as gdscript lacks the ability to "catch" errors, there should be a way to programmatically test whether I'm able to call .get_method_list() on the object before the error occurs.

[AThousandShips]

But you're not calling it on an object, you're calling it on a class

[kumikumi]

The reason I'm reporting this as a bug instead of an enhancement or proposal, is that it says that both value is Object is true and "get_method_list" in value is true, which is inconsistent with the fact that calling value.get_method_list() fails because the method doesn't exist and it's not apparently even an object.

[AThousandShips]

How is it inconsistent? It's a class, not an instance

Edit: My bad got some details confused about these instances

[AThousandShips]

The compiler has no idea what you are doing, so it can't tell you that you're doing something wrong by calling it on a class here, the error message could be improved, but what you are doing is an error and the same as calling value.nonexistent_function()

Some way to detect if a variant is a class would be helpful though

[AThousandShips]

I think it would be helpful if GDScriptNativeClass worked to provide type relationships, so you could do:

func maybe_create(type) -> Object:
    if type is Button:
        return type.new()
    return null

or

func maybe_create(type) -> Object:
    if "some_function" in type:
        return type.new()
    return null

Currently you can't even do Button is Control, but otherwise the only difference between value.get_method_list() and Button.get_method_list() is the error message

The usefulness of being able to pass classes is mixed, but I don't think this is a bug

[dalexeev]

I confirm this, we do have a problem between distinguishing between static methods of a class and non-static methods of a class as an object. And if in the case of GDScript classes we can deceive the static analyzer by casting the value to GDScript, then in the case of GDScriptNativeClass this also affects the runtime. You can obtain an unsafe value on which you cannot call methods to check its class.

I'm working on a GDType class that will allow to consolidate Godot types (Variant, objects, scripts). Here is how you can check it now:

func is_gdscript_native_class(value: Variant) -> bool:
    # More guarantees, but this is a more expensive check.
    #return var_to_str(value).begins_with("Object(GDScriptNativeClass,")
    # Let's assume that users won't shoot themselves in the foot.
    return str(value).begins_with("<GDScriptNativeClass#")

func test(object: Object) -> void:
    assert(is_instance_valid(object))
    if is_gdscript_native_class(object):
        print("GDScriptNativeClass")
    else:
        print(object.get_class())

Related:

• Can't access any methods of GDScript classes (except .new()) unless you first cast them as Script or GDScript #76414
• Classes that are exposed but lead to empty docs pages. #76918 (comment)
• Add `GDScriptType` wrapper instead of `GDScriptNativeClass` godot-proposals#6502

[kumikumi]

Thanks @dalexeev for your response and useful pointers. Turns out that the function call indeed works if you cast the value to Object first.

I have edited the original post with these code examples:

	print(value.get_method_list) # GDScriptNativeClass::get_method_list
	print(value["get_method_list"]) # GDScriptNativeClass::get_method_list
	#print("method list: ", value.get_method_list()) # Invalid call. Nonexistent function 'get_method_list' in base 'Button'
	print("method list: ", (value as Object).get_method_list()) # Works!