Add support for exporting script classes without a name

[SaracenOne]

In the current editor implementation, you can export classes with custom script types and have the correct type validation be performed for both the inspector drag and drop behaviour and the scene tree selection popup. However, you can also export classes which are not defined by custom classes, but by script path constants, but these will not be validated by either of these editor options. This PR will check the script path of nodes to determine if they match. It also checks the inheritence of scripts.

It's debatable whether this is technically a bug or not, but it deviates from standard expecting operating behaviour given what is permissible in scripting, and is generally quite annoying if you don't like defining custom class names for every minor script.

[KoBeWi]

It should show the script's icon (its own icon if set or base node type). Also instead of full path, which can be very long, I think it should be filename only.

[SaracenOne]

Okay, I'll see if I can edit this to make the result a bit more presentable

[SaracenOne]

There we go, it will now show the filename instead of the full path. It will also attempt to find the most appropiate icon, first checking the inheritence chain, and if it can't find anything, it will fall back to the icon of the base type.

[KoBeWi]

You could've used EditorData's get_script_icon(). Sorry for not mentioning it earlier .-.

[SaracenOne]

Okay, I'll update it again to use this function

[SaracenOne]

Hmm, that function appears to be bugged, doesn't return an icon from scripts that don't have any custom defined icon. I guess I'll open up another PR for that once I've tested things.

[SaracenOne]

Actually, 'fixing' this might or might not be desirable. Allowing that fuction to return the base script type changes how scripts are loaded in the inspector

[SaracenOne]

We could either:
A. Keep it as is
B. Change the script icon return function to return the base types
C. Change it so that when the type is a script type without an explicit icon, use the same cog icon as in the inspector uses currently.

[KoBeWi]

Maybe try _get_class_or_script_icon()?
EDIT:
No it's private. But there is get_class_icon(), so you could use it as fallback if script has no icon.

[SaracenOne]

@KoBeWi Okay, I've gone back to have a look at this. The solution I've landed on is basically deriving the icon during the set_valid_types method and storing it in the metadata.

		// Attempt to get the correct name and icon for script path types
		String type_name = type;
		Ref<Texture2D> type_icon = EditorNode::get_singleton()->get_class_icon(type);

		// If we can't find a global class icon, try to find one for the script.
		if (type_icon.is_null()) {
			if (ResourceLoader::exists(type, "Script")) {
				Ref<Script> node_script = ResourceLoader::load(type);
				if (node_script.is_valid()) {
					type_name = type_name.get_file();
					type_icon = EditorNode::get_editor_data().get_script_icon(node_script);
					if (type_icon.is_null()) {
						type_icon = EditorNode::get_singleton()->get_class_icon(node_script->get_class_name());
					}
				}
			}
		}

This is a bit more simplified and also solves an issue with the earlier implementation that it wouldn't use custom icons unless we defined a global class. This time, it simply attempts to get a class icon, and if it fails, it will check if a script exists for that path. If it does, it will change the type name to just the name of the script and will use the get_script_icon method. Since this doesn't work for scripts which don't have explicitly defined custom icons, I decided instead of trying to determine the base type, to just fall back on the script's class's own icon if a custom icon cannot be found. This is consistent with how script icons are displayed in the inspector and seems pretty consistent.

Basically, you now get a script icon (a cog for GDScript specifically), or you get whatever you define with icon() now displaying correctly without the need give your script an explicit class_name.

[KoBeWi]

I think there might be a better way, but at least it works.

[KoBeWi]

This could be changed to method probably, but I wonder how it could be reused in editor properties too (since it's the same).

[SaracenOne]

Updated some of the things pointed out.

[SaracenOne]

Updated now.

[KoBeWi]

The base node class icon is not displayed, generic Script icon is used:

Although that's probably a problem with get_object_icon() (though normally it's expected, because this icon shows in Script field).

[YuriSizov]

Thanks!