IssueTracker

Component used: Navigation 2.8.3

When using a serializable route, it cannot have nested serializable objects, as the navigation library throws an error. See this example below:

@Serializable
data class Route(val details: Details)
@Serializable
data class Details(val name: String, val description: String)

composable<Route> {
   ...
}

Declaring this route will throw this error:

java.lang.IllegalArgumentException: Route com.example.Route could not find any NavType for argument details of type com.example.Details - typeMap received was {}

I realize we can pass a typeMap when calling the method, but there is no NavType to match the Kotlin classes annotated with @Serializable.

Also I think we should not need to pass a typeMap. Since the object is serializable, then we don't need to do anything further than that.

For now, the workarounds I see are either:

1. Flattening the properties directly into the route, but that's not ideal if we want to share the data model around.
2. Making the nested classes Parcelable since there's a NavType for that. Still not ideal either, and I'm actually seeing another issue related to that, that I'm debugging at the moment. So it doesn't look reliable.

I hope you can improve on this, as it would make the library much simpler to use. Thank you.