React Yup Form Input field validation inside useMemo hook is not working

Question

I have a small snippet of code where a React-Form has an input field in an Edit scenario (where I need to populate the value and allow user to change the value in the input field). Once user change the value in the input field, I need to validate it as per my Yup schema.

Here is my code snippet:

    const validator = useMemo(() => {
        yup.object().shape({
            shareUser: yup.string()
                .required("Enter users separated by a semicolon.")
                .matches(/^([a-zA-Z0-9~!@#$%^&*()\\\-_. ]+;?)+$/, `Enter users separated by a semicolon.`),
        },
      )
      }, []);

       .......
    const form = useForm({shareUser: null}, validator);
       .......
     const handleChange = (event) => {
        setCurrentValue(event.target.value);  // currentValue is a useState hook.
        form.formState.shareUser = event.target.value;
        form.dirty['shareUser'] = true;
    };
       ............
     <input
        name="shareUser"
        label="Users"
        form={form}
        defaultValue={currentValue}
        onChange={handleChange }
     />

So my allowed pattern is non-empty strings like "user1;user2" or "user1;". If user types in something like "user1, user2", I am going to reject it with the validation error: Enter users separated by a semicolon.

However the issue is that: when I am putting my validator inside the useMemo hook, it's not working!

However if I move the validator outside of the useMemo, it's working.

I am not able to figure out what I am missing here.