While working on building a custom error message formatter for Joi validation errors, I noticed an inconsistency with the path attribute of unknown object keys. Nested object keys don't have the full path. For example:

Joi.validate({ key: 'value' }, {}, function (err) {
  console.log(err.details[0].path); // prints "key"
});

Joi.validate({ key: { nestedKey: 'value' } }, { key: {} }, function (err) {
  console.log(err.details[0].path); // prints "key" instead of "key.nestedKey"
});

This patch adds the full path to validation errors of unknown nested keys.