How to handle directives without arguments?

[rwysocki-equinix]

input EditWidth {
  width: BigDecimal @Positive @Digits(integer: 10, fraction: 2)
}

How to handle the Positive directive?

this format always expects arguments

directive:
   arg1: schemaApi
   arg2: ["schemaApi2", "Hello $1"]

It would be ideal to be able to define directive mapping without arguments like:

directives: {
  Positive: "positive"
}