Don't mark Stripe Link as enabled in the admin

[senadir]

Fixes #3356

Changes proposed in this Pull Request:

This PR resolves an issue in which Stripe Link would be marked as incompatible with Checkout block. To decide if a payment method is compatible or not, Checkout block would compare all registered gateways in woocommerce_payment_gateways and make sure they have a corresponding JS paymentGateway or expressPaymentGateway. Stripe Link alongside Google Pay and Apple Pay all use the same stripe express payment registry, however, in PHP, Stripe Link register its own gateway class WC_Stripe_UPE_Payment_Method_Link. This ends up marking it as incompatible.

There are several possible solutions to this, the least intrusive so far, is to mark WC_Stripe_UPE_Payment_Method_Link as disabled on all admin requests. This seems to work fine in admin and frontend, and doesn't break anything from what I saw.

Sadly changing $this->enabled broke certain unit tests that I couldn't figure out how to fix. I moved the logic to the main woocommerce_payment_gateways filter call.

This code might break any admin logic that depends on Stripe Link being marked enabled. I checked and couldn't find anything.

Another option was to limit disable to only Gutenberg pages, but it was too early to reach for get_current_screen.

Before: (those are before and after from a PR woocommerce/woocommerce#52070 but for this PR, both are considred before).

After:

Testing instructions

1. Enable Link.
2. Make sure your Checkout page is Checkout block.
3. Go to editor, select the main Checkout block, make sure the sidebar doesn't have any warnings about an incompatible plugin.
4. Do regression testing for Link, making sure it loads on both checkouts and you can place an order with it.

---

• Covered with tests (or have a good reason not to test in description ☝️)
• Added changelog entry in both changelog.txt and readme.txt (or does not apply)
• Tested on mobile (or does not apply)

Post merge

• Added testing instructions to the [Release Testing Instructions wiki page] (https://github.com/woocommerce/woocommerce-gateway-stripe/wiki/Release-Testing-Instructions) (or does not apply) (Honestly not sure how to write tests for this, as I'm not sure you have E2E flows that cover the editor).
• Added the needs docs label (or does not apply) Does not apply.
• Included this PR in the Release Thread scope (or does not apply) Not sure what is this.

[senadir]

Updated logic so it removes Link from the main gateway filter instead of adding logic in the gateway class WC_Stripe_UPE_Payment_Method_Link, for some reason that kept failing no matter what value I put in enabled, even though it was not being reset manually, the test test_upe_method_enabled didn't propogate the value to Link when flipping. WC_Stripe_Helper::update_main_stripe_settings( $stripe_settings ); setting value was not making maybe. This is even with deleting the is_admin check, just simply doing $this->enabled = self::is_link_enabled() ? 'yes' : 'no'

The check here still only does is_admin because it's too early to check for get_current_screen. I think I can have another filter down the road that reaches directly to wc()->payment_gateways to remove Link. Let's see if this causes problems. All tests passed to me.

[annemirasol]

@senadir maybe fixes #3356?

[wjrosa]

Nit-pick: I would use WC_Stripe_UPE_Payment_Method_Link::class instead, just for a more straightforward lookup and to avoid issues with class renaming.

[senadir]

Good catch!

[diegocurbelo]

Thanks for fixing this @senadir!

I could not find any side effects, all critical flows test well... (the legacy checkout E2E test is failing in guthub because of a timeout, it works fine locally.. and I also tested it manually)

[senadir]

I prematurely merged this before testing the refactor 😞 Pushing another PR to fix it. #3547