Yupで動的にバリデーションを切り替える（他の値によって）

whenを使います！

Yup.string()
    .when("firstName", {
      is: 'satoshi',
      then: Yup.string().required("Must enter email address").max(2)
    }),

https://codesandbox.io/embed/form-validation-yup-and-custom-hook-forked-m45ho?fontsize=14&hidenavigation=1&theme=dark

https://github.com/jquense/yup#mixedwhenkeys-string--arraystring-builder-object--value-schema-schema-schema