How to Modify Existing Keys in Joi Object

Question

Joi validation does not support modification of existing object keys.

I am using Joi validation for parent and child classes. The validation for the parent is the base validation for all children, but each child has specific restrictions or additional fields. I want to be able to just take my parent Joi object and be able to modify existing keys to fit certain restrictions.

//Declare base class with an array at most 10 elements
const parent = {
    myArray: Joi.array().max(10)
}
//Now declare child with minimum 1 array value
const child = parent.append({
    foo: Joi.string(),
    myArray: Joi.array().min(1).required()
})

The above code works as expected - meaning the child object does not keep the .limit(10) restriction applied to the parent. But, I want it such that it does. I'm sure append is not the right function to use here, but I am not sure of how to do this. I want my resulting child validation to look like:

const child = {
    foo: Joi.string(),
    myArray: Joi.array().max(10).min(1).required()
}

Stock Overflaw Stock Overflaw · Accepted Answer · 2019-01-30T12:53:34

Have you tried:

const child = parent.append({
    foo: Joi.string(),
    myArray: parent.myArray.min(1).required()
});

Just tried:

const Joi = require('joi');

const parent = {
  x: Joi.array().max(10).required()
};

const child = Object.assign({}, parent, {
  x: parent.x.min(1).required(),
  y: Joi.string()
});

Joi.validate({
  x: [],
  y: 'abc'
}, child); // fails as .min(1) not satisfied

Joi.validate({
  x: [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1],
  y: 'abc'
}, child); // fails as .max(10) not satisfied

Joi.validate({
  x: [1],
  y: 'abc'
}, child); // OK

Tried with a fresh npm i joi (package says: "joi": "^14.3.1"), on Node v8.10.0. Or maybe the example you gave is too trivial to reflect your real scenario?

How to Modify Existing Keys in Joi Object

1 Answers