Do not return Amazon Pay payment method form if an order has a $0 total [#2933997]

Problem/Motivation

Currently, the Amazon payment method does not take into consideration discounts or coupons that might have been added after the user has begun the Checkout process. For example,

Prerequisites:
- Billing address pane on Checkout page
- Payment pane on Review page
- Do not require payments at checkout, and show a message

Create a new Gift Card that covers your order total.
Choose Amazon Pay at the cart page
Apply the coupon at Checkout
Proceed to the Payment/Review page

In this example, the Amazon Billing Page will appear. This is because the Amazon Pay method puts a payment method callback into a hook_form_alter() implementation. The result is that, even if Rules are configured to not show the Amazon Pay method if an order is not free, the message "Payment is not required for your order" appears as well as the wallet widget.

I should note that this used to work better, but I believe some recent changes to how discounts are calculated has surfaced this issue (possibly a regression). However it still seems weird that the LPA module would still return a form despite Rules evaluating to FALSE.

Proposed resolution

Verify that the order total is greater than zero before returning a pane form.

User interface changes

None

API changes

Minor condition added

Comment	File	Size	Author
#2	2933997-commerce_lpa-free_orders.patch	1 KB	torgosPizza
#2

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Comments

Comment #1

2 January 2018 at 21:45

torgosPizza created an issue. See original summary.

Comment #2

torgosPizza

he/him

English

Portland, OR

CreditAttribution: torgosPizza as a volunteer commented 2 January 2018 at 21:48

Title:

Do not show Amazon Pay payment method for free orders.

» Do not return Amazon Pay payment method form if an order has a $0 total

File	Size
2933997-commerce_lpa-free_orders.patch	1 KB

Updating the title a bit, and here's a patch.

Comment #3

mglaman

English

WI, USA

CreditAttribution: mglaman at Centarro commented 17 May 2020 at 16:57

+++ b/commerce_amazon_lpa.module
@@ -472,6 +472,14 @@ function commerce_amazon_lpa_form_alter(&$form, &$form_state, $form_id) {
+    // Exit if the order is actually free.
+    $order_total = $order_wrapper->commerce_order_total->value();

Should we run this first, commerce_order_calculate_total? Or I suppose it is already calculated when entering checkout.