In Scala too well grown libraries return errors via sum types, e.g. Either. In Play this is actually something like JsSuccess/JsError, not an exception, altho

In Scala too well grown libraries return errors via sum types, e.g. Either. In Play this is actually something like JsSuccess/JsError, not an exception, although Play is pragmatic (aka dirty) at times, so it's possible that it has functions throwing exceptions.