Hapi/Joi validation with nested object

Question

I have the following validation on one of my routes:

payload: {
    keywordGroups: Joi.array().items(Joi.object().keys({
        language: Joi.string().requi         


        

Answer 1

You need to use Joi.alternatives() otherwise you will create a circular dependency as described in this issue.

In your is condition in the when(), you need to specify a Joi type instead of just an empty array. This example works:

import * as Joi from 'joi';

var arraySchema = Joi.array().items(Joi.object().keys({
    first: Joi.array().items(Joi.number()).default([])
        .when('second', {is: Joi.array().length(0), then: Joi.array().items(Joi.number()).required().min(1)}),
    second: Joi.array().items(Joi.number()).default([])
}));

var altArraySchema = Joi.array().items(Joi.object().keys({
    first: Joi.array().items(Joi.number()).default([]),
    second: Joi.array().items(Joi.number()).default([])
        .when('first', {is: Joi.array().length(0), then: Joi.array().items(Joi.number()).required().min(1)}),
}));

var obj = [
    {
        first: [],
        second: []
    }
];

var finalSchema = Joi.alternatives(arraySchema, altArraySchema);

var result = Joi.validate(obj, finalSchema);

console.log(JSON.stringify(result, null, 2));

The variable obj will fail the validation because both first and second are empty. Making either of them non-empty will pass the validation check.