fix(modal-checkout): add custom modal checkout validation

[chickenn00dle]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

This PR moves the modal checkout validation request to newspack blocks. We still call WC_Checkout::process_checkout, but beforehand we override the needs payment flag so that step 1 of modal checkout doesn't validate payment method (not needed at this point).

How to test the changes in this Pull Request:

1. Smoke test modal checkout using various supported payment methods, as a logged in and logged out reader:

• Stripe
• WCPay
• PayPal Payments

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[laurelfulford]

Thanks for tackling this, @chickenn00dle!

I worked through all the payment gateways you listed, and the only issue I ran into is PayPal Payments now shows a "Proceed to PayPal" button:

When I switch back to trunk, the button goes away. The Yellow button works as expected; the Proceed to PayPal button technically works, but it's kind of weird - it loads the form inside of the checkout modal, and then redirects to a full screen to authenticate, then into a non-modal order confirmation.

Just let me know if this doesn't match what you're seeing and I'll see if I can recreate it elsewhere!

[chickenn00dle]

Thanks for the review @laurelfulford!

When I switch back to trunk, the button goes away. The Yellow button works as expected; the Proceed to PayPal button technically works, but it's kind of weird - it loads the form inside of the checkout modal, and then redirects to a full screen to authenticate, then into a non-modal order confirmation.

Good catch!

I was checking $wp_script->src when iterating through $wp_styles so the paypal css assets were missing 🤦 .

Fixed in 93392a5

[chickenn00dle]

@miguelpeixe, I'd love your opinion on this approach for "hijacking" the form validation from Woo. In particular, do you think its safe to rename the woocommerce-process-checkout-nonce on the front end, then reassign in the backend before triggering WC_Checkout::process_checkout?

[chickenn00dle]

Seems this is no longer needed, so gonna close this one!