AsyncValidator deal with Future failure while using ruleField

[rwalerow]

At the moment AsynValidator api doesn't provide a way to deal with Future errors while using ruleField.

It would be nice to give users a possibility to handle error cases somehow similar to regular rule method.

• def ruleCatchOnly(...)
• def ruleCatchNonFatal(...)

How about something like this?:

• def ruleFieldCatchOnly(...)
• def ruleFieldCatchNonFatal(...)

If it were possible it would also be nice to give users a possibility to default future error handler for all field validators. With that in mind, the user could handle all errors similarly without additional boilerplate.

Example proposition:

def isUsernameUniquie(username: Username): Future[Boolean] = ???
def isEmailUnique(email: Email): Future[Boolean] = ???

implicit val userValidator = Validator[User]
    .async
    .filedErrorHandler(throwable => "Error ocurred")
    .ruleField('username, isUsernameUniquie, "Username not unique")
    .ruleField('email, isEmailUnique, "Email not unique)