Custom error messages for helpers?

[kentcdodds]

Thanks for the library!
Is there a reason the helpers (like CheckboxAsString) are not functions I can call to pass extra config (like an error message)? How would I specify my own error message?

[rileytomasek]

There isn't a good reason and I've been meaning to fix this for a while. They also don't work with .transform().

A PR would be much appreciated and should be straightforward.

[kentcdodds]

If I end up pursuing this then I'll be happy to. Thanks!