Joi array Object validation based on root key value

Question

I have a complex scenario that I want to validate using Joi here sample Joi Object Schema

const itemSchema = Joi.object({
    product_id: Joi.string().required(),
    quantity: Joi.number().required().min(0)
});

let objSchema = {
    items: Joi.array().items(itemSchema).required().min(1),
    item_return_flag: Joi.string().optional().valid(true, false)
};

depending opon item_return_flag key value true or false , I want to change the items.quantity min value requirement. When true , quantity will be 0 , otherwise it will be 1.

Is there anyway, to control the definition of validation of the object in an array, based on the root object in Joi

Answer 1

It looks to me like you could, following the API docs , do something like this:

let objSchema = {
     items: Joi.array().items(Joi.object({
         product_id: Joi.string().required(),
         quantity: Joi.alternatives().when('item_return_flag', {
              is: true, then:  Joi.number().required().min(0), 
              otherwise: Joi.number().required().min(1)
         })
     })).required().min(1),
     item_return_flag:  Joi.string().optional().valid(true, false)
};

I'm not 100% sure that's the exact correct structure, but it's close. The Joi.alternatives() is provided for just such use cases.

Answer 2

The sample code that will switch the schema based one the parent key item_return_flag . Schema of the array need to switch based using Joi.altertnatives()

let itemArr = Joi.object({
    product_id: Joi.string().required(),
    quantity: Joi.number().required().min(0)
});

let itemArr2 = Joi.object({
    product_id: Joi.string().required(),
    quantity: Joi.number().required().min(1)
});

let itemSchema = Joi.alternatives()
    .when('item_return_flag', { is: true, then: Joi.array().items(itemArr).required().min(1), otherwise: Joi.array().items(itemArr2).required().min(1)}) ;

let objSchema = {
    items: itemSchema,
    item_return_flag: Joi.string().optional().valid(true, false)
};