Add option to specify array of exactly length n and add types for such

I am creating a factory which churns out schemas for objects, and one of the schema validations is an array of homogeneous types of exactly length n, if this wasn’t done at scale it’d be something like this:

type TExample = [string, string, string]

Yup has a nice-enough way of enforcing array length and type, let’s say for the first object object1 I need it to have an array of strings exactly 3 long:

const kvSettings = {
  object1: 3
}

// validation would then be
const shapeObject1 = yup.object().shape({
  args: yup.array().of(yup.string()).test('test arg length', '', (v: []) => v.length === kvSettings.object1),
})

That validation works but the inffered types incorrectly report a type of string[] for the array instead of [string, string, string]. This happens too with the less graceful double .min(3).max(3) syntax.

type Test = yup.InferType<typeof shapeObject1>

// type Test = {
//   args: string[];
// }

Yup should infer the types correctly as [string, string, string].

[abdielalvarez]

Hello everyone, if what you wan’t is to define a maximum length do this const maxLength = 5 Yup.array().max(maxLength, 'too long')

if you want a minimum do this

const minLength = 1 Yup.array() .min(minLength, 'too short') .required('it is required')

at least you want to specify a type, this is my solution, i hope that helps someone 😃

[JimTeva]

@tsujp not sure it is working properly with latest typescript. I have typescript 4.3.5 and this below code still gives type “boolean[]” instead of “[boolean, boolean, boolean, boolean, boolean]”

deliveryWeekDays: yup
    .array()
    .of(yup.boolean().required())
    .required()
    .length(5)

@jquense any idea?