unique yup fields

unique.ts

import * as Yup from 'yup'
import { ObjectShape } from 'yup/lib/object'

declare module 'yup' {
    interface ObjectSchema<TShape extends ObjectShape> {
        unique(uniqueKey: string, message: string): ObjectSchema<TShape>;
    }
}

Yup.addMethod(Yup.object, 'unique', function (uniqueKey: string, errorMessage: string) {
    return this.test('unique', { [uniqueKey]: errorMessage }, function (object) {
        if (!Array.isArray(this.parent)) {
            throw new Error('unique requires the parrent to be an array')
        }
        // eslint-disable-next-line @typescript-eslint/no-unsafe-member-access
        const nonUniqueItems = this.parent.filter((item: any) => item[uniqueKey] === object[uniqueKey])
        // return false to show the error message
        // it is valid only if one item exist in nonUniqueItems
        return nonUniqueItems.length === 1
    })
})

export const userSchema = Yup.object().shape({
    formValues: Yup.array().of(
        Yup.object().shape({
            name: Yup.string()
                .min(3, 'errors.shortname')
                .required('errors.required'),
            email: Yup.string()
                .email('errors.email')
                .required('errors.required'),
        }).unique('email', 'Duplicate email address')
    )
})