Using Joi, require one of two fields to be non empty

Question

If I have two fields, I\'d just like to validate when at least one field is a non empty string, but fail when both fields are empty strings.

Something like this does

Answer 1

Code below worked for me. I used alternatives because .or is really testing for the existence of keys and what you really wanted was an alternative where you would allow one key or the other to be empty.

var console = require("consoleit");
var Joi = require('joi');

var schema = Joi.alternatives().try(
  Joi.object().keys({
    a: Joi.string().allow(''),
    b: Joi.string()
    }),
  Joi.object().keys({
    a: Joi.string(),
    b: Joi.string().allow('')
    })
);

var tests = [
  // both empty - should fail
  {a: '', b: ''},
  // one not empty - should pass but is FAILING
  {a: 'aa', b: ''},
  // both not empty - should pass
  {a: 'aa', b: 'bb'},
  // one not empty, other key missing - should pass
  {a: 'aa'}
];

for(var i = 0; i < tests.length; i++) {
  console.log(i, Joi.validate(tests[i], schema)['error']);
}