Allowing using ChildOf directly inside bsn! macro

[eckz]

Objective

If I want to spawn a scene as a child of an entity that already exists, the current api doesn't offer an straightfoward solution.

The easies I found is by doing something like this:

const my_entity = ...;
commands.spawn_scene(bsn! {
    template(move |_| Ok(ChildOf(my_entity)))
    scenes::list_item(text)
});

Solution

• Deriving directly FromTemplate for ChildOf.
• Adding a new variant to EntityReference.
• This allows code like this to work directly

fn scene(root: Entity) -> impl Scene {
    bsn! {
        ( #Child1 ChildOf(root) ),
    }
}

Testing

• Running unit tests locally.

[cart]

This is a good call! Same general ideal as HandleTemplate::Handle. I renamed EntityReference::SpecificEntity to EntityReference::Entity.

[alice-i-cecile]

Cool! That's a nice idea. Thanks for adding a test.