Joi schema.validate a custom type return an undefined value

Question

I'm trying to validate a custom Type with JOI all with conversion. the base type of my JoiType is a Joi.array()

when I try to

const schema = Joi.object().keys({
 attribute: Joi.array().items(Joi.string())
});

const result = schema.validate(exampleOfArray);

I found that result.value contains the real validated value.

But when I change the type to a custom type, the value is not returned : (result.value === undefined)

here is my custom type :

const customJoi = Joi.extend((joi: Root) => {
  return {
    type: 'stringArray',
    base: joi.array().items(joi.string()).meta({ baseType: 'array' }),
    coerce(value: any, helpers: CustomHelpers) {
      if (typeof value !== 'string') {
        return value;
      }
      if (!value) {
        return [];
      }
      return value.replace(/^,+|,+$/mg, '').split(',');
    }
  };
});

const schema = Joi.object().keys({
 attribute: customJoi.stringArray().items(Joi.string())
});

Answer 1

I have found the solution:

the coerce function should return :

return { value: value };

instead of :

return value;