yup fields required only if other fields are filled in - formik

Question

I use Yup for my Formik form validation.
I have the following contact form :
const contactForm =
{
title: undefined,
firstName: '',
lastName: props.contact?.name,
contactGroup: {
phone: props.contact?.phone || '',
email: props.contact?.email || '',
},
};
when I fill in the fields I would like the lastName field to go to error only when one of the other fields is filled in.
Here is the validation scheme I use to handle form errors
const schema = yup
.object()
.shape<any>({
firstName: yup.string().max(256, 'max-length'),
lastName: yup.string().when(['email', 'phone', 'firstName'], {
is: (email: any, phone: any, firstName: any) =>
email && phone && firstName,
then: yup.string().required('empty').max(256, 'max-length'),
}),
contactGroup: yup.object().shape<any>(
{
phone: yup.string().when('email', {
is: (email: any) => !email || email === '',
then: yup.string().max(256, 'max-length'),
}),
email: yup
.string()
.nullable(true)
.when('phone', {
is: (phone: any) => !phone || phone === '',
then: yup.string().email('invalid').max(256, 'max-length'),
}),
},
[
['phone', 'email'],
['email', 'phone'],
]
),
})
.required();
I modified the yup in the following way:
lastName: yup.string().when(['email', 'phone', 'firstName'], {
is: (email: any, phone: any, firstName: any) =>
email && phone && firstName,
then: yup.string().required('empty').max(256, 'max-length'),
}),
here I ask if the fields email, phone and firstName are filled in the field lastName is set in error.
It works if I do it only on firstName, but if I add email and phone it doesn't work anymore.
I think it comes from the fact that phone and email are in a contactGroup subobject
Is there a solution for this problem ?
lastName should only go into error when one of the fields phone, email or firstName is filled in.