WooCommerce Checkout: make fields (not) required depending on payment option - php

Question

The requirement:
Depending on the chosen payment option, certain checkout fields should not be required.
My scenario:
It clients select "local pickup" they get the option to select PayPal, credit card etc. and "pay at pickup".
If they pay at pickup, we don't need they payment address. The invoice will be handled at pickup and the checkout is actually a reservation.
I have found a solution myself and share this question as a reference.
Find the solution in an answer.

Answer 1

This is my solution:
add_action( 'woocommerce_checkout_process', 'gw_deactivate_some_fields_on_condition');
function gw_deactivate_some_fields_on_condition() {
add_filter( 'woocommerce_checkout_fields' , 'gw_some_billing_fields_not_required_for_cash_on_delivery_payment_method' );
}
function gw_some_billing_fields_not_required_for_cash_on_delivery_payment_method( $fields ) {
$chosen_payment_method = WC()->session->get('chosen_payment_method');
if ( 0 === strpos( $chosen_payment_method, 'cash_on_delivery' ) ) {
$fields['billing']['billing_address_1']['required'] = false;
$fields['billing']['billing_address_2']['required'] = false;
$fields['billing']['billing_city']['required'] = false;
$fields['billing']['billing_postcode']['required'] = false;
$fields['billing']['billing_country']['required'] = false;
$fields['billing']['billing_state']['required'] = false;
}
return $fields;
}
add_action( 'woocommerce_after_checkout_form', 'gw_disable_payment_fields_if_local_payment' );
function gw_disable_payment_fields_if_local_payment( $available_gateways ) {
?>
<script type="text/javascript">
jQuery( document ).ready(function() {
show_hide_payment_options();
});
jQuery('form.checkout').on('change','input[name^="payment_method"]',function() {
show_hide_payment_options();
});
jQuery('form.checkout').on('change','input[name^="shipping_method"]',function() {
show_hide_payment_options();
});
function show_hide_payment_options() {
var val = jQuery('input[name^="payment_method"]:checked').val(); // If it changed, then it must be the radio options so check the one that's selected
var fields_selector = '#billing_country_field, #billing_address_1_field, #billing_address_2_field, #billing_city_field, #billing_postcode_field';
if (val.match("^cash_on_delivery")) {
jQuery( fields_selector ).fadeOut();
} else {
jQuery( fields_selector ).fadeIn();
}
}
</script>
<?php
}
For handling the shipping fields see this post:
https://www.businessbloomer.com/woocommerce-hide-shipping-local-pickup-selected/
This was also a strong inspiration for my code.