Manual invocation for deriving a CantonConfigValidator instance from a CantonConfigPrevalidator instance (found by implicit resolution) for the configuration A and all its subconfigurations unless implicit resolution already finds a CantonConfigValidator instance for them. Implicit resolution must also find CantonConfigPrevalidator instances for all subconfigurations of A for which derivation happens.

manual.CantonConfigValidatorDerivation should be preferred when possible because it is more predictable and usually more efficient. In particular, derivation failures can be hard to debug for semi-automatic derivation. For example, suppose that A is a case class Foo with a field i: Option[Bar] where implicit resolution does not find a CantonConfigValidator instance for Bar. The derivation sees that Option is a sealed trait of case classes None and Some and therefore attempts to derive a CantonConfigValidator instance for None and Some. The derivation for None will fail though because there is no CantonConfigPrevalidator instance for None. This makes the overall derivation fail with a rather obscure error message about implicit resolution problems.