Express payment method inconsistencies with subscription flows

[frosso]

Description

I noticed some inconsistencies when it comes to subscriptions & express payment methods. I wanted to collect them here and start discussing whether they were missed features or there was some business logic reasoning behind it.

Express payment methods not available on "change payment" page

As a customer, I can place an order with a subscription item and pay with Google Pay/Apple Pay.
If I go to the page to manage the subscription to change the payment method, I don't have an option anymore to pay with Google Pay/Apple Pay.

Express payment method not reported correctly in subscription details

If a customer places an order containing a subscription item, their payment method is saved and associated with the merchant's website.
However, the payment method is reported as "Visa" or "Mastercard" (or other), instead of "Google Pay"/"Apple Pay".

This behavior seems inconsistent with the reporting made when the same order is placed without a subscription item.

Acceptance criteria

[pierorocca]

Stripe is showing that both support recurring billing. It's not clear if that that's only using Stripe's subscription billing engine or in general. Ultimately I believe a payment instrument is linked to the card token and the wallet is allowing a shopper to select another card, to update the payment instrument. I don't believe the wallet can be left as the payment method but it could be used to pick a new card to put on file.

Team Quark I assume would have more experience and history with this?

[pierorocca]

Google seems to be compatible. Apple Pay requires use of Apple's merchant tokens. https://docs.stripe.com/apple-pay?platform=web#recurring-payments

[frosso]

Express payment methods not available on "change payment" page

I investigated this flow today, as part of #11144 , making sure I didn't introduce any new bugs (or making sure I could fix something on the side).
Unfortunately, it's not possible to leverage the Store API (which are currently used in the "order pay" feature used by WC Subscriptions) to attach a new SI to an order.
Any attempt results in a "let's process the payment now". Which fails to process because of the invalid order status.

So, while I was able to make the button display on the page and having it create a Setup Intent, it's not possible to attach this new setup intent via the Store API exposed by WC Core or WC Subscriptions.

So it makes sense to currently hide the button.

Express payment method not reported correctly in subscription details

It now consistently shows "Cards", whether it's a Google Pay or a "UPE Visa card".
So since there's no longer inconsistency, I think we're good.