YUP: Validate that items in an Array match one of multiple allowed Schemas

yup_array_oneOfSchemas.js

/**
 * The yup library has no builtin way to check if items in an array
 * match one or more defined shapes, we can only check against a set of
 * whitelisted values using yup.array().oneOf([..]).
 *
 * Using yup.addMethod() and yup.mixed().test() however we can pretty
 * much add any custom validation we want. The function below allows to
 * make validation pass for array items of different shapes.
 */

const assert = require('assert');
const yup = require('yup');

// Please note this method is sync. An async version would return a Promise.

yup.addMethod(yup.array, 'oneOfSchemas', function(schemas) {
  return this.test(
    'one-of-schemas',
    'Not all items in ${path} match one of the allowed schemas',
    items => items.every(item => {
      return schemas.some(schema => schema.isValidSync(item, {strict: true}))
    })
  )
})

// Usage example below. Run like: $ nodejs yup_array_oneOfSchemas.js

const Beer = yup.object().noUnknown().shape({
  'alcoholConcentration': yup.number(),
})

const Water = yup.object().noUnknown().shape({
  'sparkling': yup.boolean(),
})

const Crate = yup.object().noUnknown().shape({
  // Any item in the array must match either the Beer or Water schema.
  'bottles': yup.array().oneOfSchemas([Beer, Water]),
})

const crate = {
  bottles: [
    {'sparkling': true},
    {'alcoholConcentration': 5},
  ]
}

assert.strictEqual(Crate.isValidSync(crate, {strict: true}), true)

This is how we finally did it, we created a new method called 'requiredByAssertion', which allows us to require some fields based on another field value assertion.

Following the last example:

yup.addMethod(yup.mixed, 'requiredByAssertion', function ([fields, assertion]) {
  return this.when(fields, {
    is: (...args) => assertion(...args),
    then: (obj) => obj.required(),
  });
});

const isType1 = [['type'], (type) => type === 'type1'];
const isType2 = [['type'], (type) => type === 'type2'];

const serviceSchema = yup.object().shape({
  type: yup.string().oneOf(['type1','type2']).required(),
  code: yup.string().min(6).required(),
  number: yup.string().min(5).required(),
  amount: yup.number().required().positive().integer(),
  field1: yup.string().url().required(),
  date: yup.string().requiredByAssertion(isType1),
  dateDelivery: yup.string().requiredByAssertion(isType2),
  field2: yup.object({
    field3: yup.string().required(),
  }).default(null).nullable().requiredByAssertion(isType1),
  field4: yup.object({
    field5: yup.string().required(),
  }).default(null).nullable().requiredByAssertion(isType2),
});

const schema = yup.object().noUnknown().shape({
  name: yup.string().required(),
  code: yup.string().required(),
  services: yup.array().min(1).of(serviceSchema),
});