Fix handling for "no such customer" response for customer payment_methods query

[daledupreez]

Related to #4560

Changes proposed in this Pull Request:

This PR ensures that when we receive an HTTP error from the Stripe payment_methods API, we now check if the customer doesn't exist based on the error.type, error.param, and error.code fields in the response from Stripe. If the customer doesn't exist, we now populate the cached data with an empty array to prevent unnecessary repeat calls to Stripe.

Testing instructions

• Set up a test site that uses a test connection to Stripe using the code from trunk
  • To really see the problem, you can also enable Optimized Checkout and ensure you're using block checkout
• While logged in as a user, make a purchase (or perform another action) to get a Stripe customer ID assigned to your user
• Install a plugin like Debug Bar so you can see what HTTP requests are being made from PHP during page loads
• Add another product to your cart, and navigate to checkout -- keep this tab open
• Use Debug Bar to inspect the outbound HTTP requests for the site -- you may or may not see a number of HTTP requests to the Stripe payment_methods API
• Now reconnect Stripe and use a different test Stripe account
• Reload your checkout tab
• Inspect the outbound HTTP requests -- you should see a number of calls to the Stripe payment_methods API that all return 400 statuses
• Reload your checkout tab again, and verify that all the payment_methods API calls are repeated
• Now load the code from this branch
• Reload your checkout tab, and verify that all the payment_methods API calls are repeated
• Now load the checkout tab again, and verify that no payment_methods API calls are made, as we now have the data cached

---

• Covered with tests (or have a good reason not to test in description ☝️)
• Tested on mobile (or does not apply)

Changelog entry

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Changelog Entry Comment

Comment

Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)

[Copilot]

Pull Request Overview

This PR fixes an issue where the Stripe payment methods API repeatedly fails when a customer doesn't exist in Stripe, by properly caching empty results to prevent unnecessary repeat API calls.

• Adds error handling to detect when a Stripe customer doesn't exist based on specific error response fields
• Caches an empty array result when a customer is missing to prevent redundant API calls
• Updates changelog and readme to document the fix

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
includes/class-wc-stripe-customer.php	Adds error detection logic and caching for missing customers in payment methods API
readme.txt	Documents the fix in the readme changelog
changelog.txt	Records the fix in the main changelog

[malithsen]

Nice find. I've replicated the issue and can confirm it's fixed on this branch.

[wjrosa]

Nice fix, Dale! Looks good to me ✅