Makes EditorView non-nullable in useLayoutGroupEffect and useEditorEventCallback

[coolov]

What?

Currently the view prop in useLayoutGroupEffect and useEditorEventCallback is nullable, this means that we need to assert that the value exists before using it:

const onClick = useEditorEventCallback((view) => {
  if (view) {
    // do things
  }
});

By making the value non-nullable we no longer need this check!

How?

This PR proposes that we only fire the callbacks in the effects if view is set. This way we can guarantee that the value is never null and always of type EditorView.

So why is the value sometimes null in the first place? This has to do with how the initial render bootstraps the EditorContext that holds the EditorView. See @smoores-dev comment in this thread:

On the first render pass, the view will be null, because it's constructed in a layout effect. That means that we sort of have to type the context as returning an optional view, even though in practice, I think it would always be defined by the time the callback actually runs.

For more details about how the creation of the EditorContext is deferred, see useEditorView

[smoores-dev]

Awesome, thanks @coolov. I actually think this is a pretty big win; more than one user has expressed confusion or annoyance that the view might be null.

This feels good to me, though as @tilgovi pointed out in the other thread, undoing this would be a breaking change, so it's worth thinking about critically. @tilgovi, did you have any other thoughts you wanted to raise on the topic?