io.eezo

The entry point an application on the umbrella extends: both layers, one trait, one package.

object Main extends EezoApp {
 override def schema: Schema     = AppSchema
 override def routes: RouteTable = Routes.table()
}

Nothing here is new: HttpApp brings routes, the server's overrides, boot's default of serving, and the dev and routes commands; LiveApp brings the live socket and client, so Live.mount works with no configuration; DbApp brings schema, the database lifecycle, and the schema commands. boot is concrete in HttpApp and abstract in DbApp, so an application inherits "serve" regardless of which of the two supertypes below is written first, and a Main that overrides boot still wins.

What is this trait's own is the one idea both overrides spell: the http layer runs under the database. program is concrete in both layers, boot() in one and withDatabase(boot()) in the other, so the compiler refuses any trait that stacks the two until it overrides program and says which; this one says the database layer's. A user's own extends DbApp with HttpApp fails the same way, in either order, instead of booting with no Database installed. dev composes through devServer alike: the drift check before the server comes up, and the refusal page in place of the app while the drift is dangerous, all under the same Database.