Session variable 'chosen_shipping_methods' not updating

[coycash]

Describe the bug

I have my own plugin which checks for the currently chosen shipping method on ajax update by way of the following code:

function wtld_checkout_addons_process() {
   $chosen_shipping_method_id = WC()->session->get( 'chosen_shipping_methods' )[0];
   // ...
}
add_action('woocommerce_checkout_process', 'wtld_checkout_addons_process');

This works on WooPayments 7.4.0 and earlier but after 7.5.0 $chosen_shipping_method_id is never updated/changed from the initial selection.

To Reproduce

1. Go to 'Checkout' under WooPayments 7.5.0 or 7.6.0
2. Change from 'flat_rate' to 'local_pickup' shipping method
3. woocommerce_checkout_process hook still says 'flat_rate' is selected
4. Rollback to WooPayments 7.4.0
5. Works fine

Desktop (please complete the following information):

• OS: Windows 10
• Browser: Firefox
• Version: 125.0.3

Additional context

Originally posted woocommerce/woocommerce#47295

[gpressutto5]

Hi @coycash! I'm using WooPayments 7.6.0, but I still can't reproduce the issue following the steps you provided. Should I do anything differently?

[coycash]

I can't quite see the bottom or your screen but it looks like you are submitting the order. I am not submitting the order and checking the ajax response but rather checking the value of 'chosen_shipping_methods' server side after an ajax call. Does that make sense?

[gpressutto5]

Hi @coycash. Yes, I'm submitting the order because that's the only way I found to make the woocommerce_checkout_process hook run. Have you found another way?
Could you update the "To Reproduce" steps with everything we need to reproduce the issue or provide a repository that reproduces it?