I'm hitting into this when creating Joi schemas for forms, where I have a text input which can optionally be filled in, but if it's not, then no problems.

At the moment I have to use the work around of:

Joi.string().valid('').optional() // followed by any other validations

This is due to this line: https://github.com/hapijs/joi/blob/master/lib/string.js#L19

I'd be inclined to argue that if you've just said Joi.string() without any optional or required tags, then an empty string is actually a valid value. If you say it's required, then an empty string would be invalid.

Thoughts?