Support for arguments that require each other but are optional

Similar to the MutuallyExclusiveSet, it would be very helpful to be able to specify that if argument A is specified then argument B is required, but if A is not specified, then B is optional.

This may be a very specific use case, and I wouldn't even pursue it, but I'm having difficulty using the built in HelpWriter when my additional validation fails, since this validation is outside of the normal flow.

An alternative would be to support passing a Function to something like parser.CustomValidation() where the developer could get the parsed options (that were properly parsed) and run additional validation checks. If a check fails the developer can raise an exception.

Commencez par localiser les implémentations existantes de MutuallyExclusiveSet et HelpWriter, puis examinez comment les options analysées et les échecs de validation transitent par le parseur. Comparez les arguments optionnels dépendants demandés avec la fonction CustomValidation proposée ; le travail est considéré comme terminé lorsqu’un comportement convenu est implémenté et que sa gestion de l’aide et des erreurs est couverte par des tests.

Rédigé par le modèle d'indexation à partir du texte de l'issue.