Inspector: Fix clearing array/dictionary element with <Object#null>

[dalexeev]

• Fixes Clearing one of the values of TypedArray in the inspector makes the value unable to be found by the find function #82716.

EditorPropertyArray and EditorPropertyDictionary use EditorPropertyResource and EditorResourcePicker, but array elements and dictionary keys/values can be Variant() (null), unlike Ref<Resource>.

godot/editor/editor_resource_picker.cpp

Lines 346 to 350 in 93cdacb

	case OBJ_MENU_CLEAR: {
	edited_resource = Ref<Resource>();
	emit_signal(SNAME("resource_changed"), edited_resource);
	_update_resource();
	} break;

[KoBeWi]

I don't really understand the issue. Assigning Variant() in EditorResourcePicker does not fix it 🤔 Why is it different initially?

[dalexeev]

Because a Variant can store both Variant() and Ref<Resource>(), but a Ref<Resource> cannot store Variant(), it will be implicitly cast to Ref<Resource>(). This is a flaw in the type system, we have three nulls: null (Variant()), Object#null and FreedObject. The first one is Variant::NIL, the last two are Variant::OBJECT.

[KoBeWi]

But the array works correctly when first resized. So it has a different value than after using Clear it seems, and there is no way to restore it.

[dalexeev]

To resize, the editor probably calls the array method, which works correctly. Copying Object#null value from the editor only occurs on write actions (not on read actions), when you interact with the element's editor.

[KoBeWi]

Maybe the comment should be more descriptive ("GH-#" is very specific, but it requires you to lookup the issue).

[YuriSizov]

@dalexeev Would you mind updating the comment to say a bit more about the reason for the code's existence? You can still add See GH-... at the end.

[dalexeev]

@YuriSizov Added comments and rebased the branch.

[akien-mga]

Thanks!

[YuriSizov]

Cherry-picked for 4.2.1.