Q: how to make custom type narrowing validator (i.e. Predicate<x>)? about ow HOT 3 OPEN

The best we now have is this

  class ABPredicate extends Predicate<AB> {
    constructor() {
      super('string');
      this.addValidator({ validator: isAB, message: (value, label) => 'TODO' });
    }
  }

and it does fulfill our purpose from what we can tell. At least the value's type is narrowed to AB after the ow() call.

But this way, the validator function isAB is given a value to assert that's already cast by ow to AB instead of the string or unknown that we'd expect, suggesting that this is either an ow API weakness or this implementation does something backward.

from ow.

ow.create is meant for creating custom validators. I don't remember whether it would solve your needs though. I also don't have time to actively maintain this package anymore (meaning, I'm happy to accept PRs, but cannot commit time to new features), so you may be better off finding a different package with a more active maintainer.

from ow.

So I gather from you bringing that up that what we want would be a new feature, it's not really that we're missing something. Was afraid of that... I might put in the time to make a pr, I do love this lib compared to e.g. joi.

from ow.