Yup Custom Validation (addMethod) Bug

Describe the bug Code breaks when adding custom validation logic via addMethod function.

Code returns : vendors-node_modules_apollo_client_index_js-node_modules_hookform_resolvers_yup_dist_yup_modu-7f163c.js:9521 Uncaught (in promise) TypeError: Cannot read property ‘reduce’ of undefined message.

To Reproduce Just add custom validation to yup

yup.addMethod(yup.object, 'localeEqual', function (errorMessage) {
    return this.test('locale-equal', errorMessage, function (value) {
        const {path, createError} = this
        return value.kz.length === value.ru.length || createError({path, message: errorMessage})
    })
})

CodeSandbox https://codesandbox.io/s/yup-custom-validation-error-41x1n?file=/src/App.js

[jorisre]

You got that error because value could be undefined, here is the fixed part:

yup.addMethod(yup.object, "localeEqual", function (errorMessage) {
  return this.test("locale-equal", errorMessage, function (value) {
    const { path, createError } = this;
    return (
      value.en?.length === value.ru?.length || // <= Fixed line with optional chaining
      createError({ path, message: errorMessage })
    );
  });
});

This line: value.en?.length === value.ru?.length

Let me know if you still have the issue

[jorisre]

Thanks so much, @sanzhardanybayev that’s awesome to hear!