MOL-1297: Fix payment method cache in production

src/Resources/config/services/subscriber.xml

@@ -63,5 +63,12 @@
             <argument type="service" id="mollie_payments.logger"/>
             <tag name="kernel.event_subscriber"/>
         </service>
+
+        <service id="Kiener\MolliePayments\Subscriber\PaymentMethodRouteCacheKeySubscriber">
+            <argument type="service" id="Shopware\Core\Checkout\Cart\SalesChannel\CartService"/>
+            <tag name="kernel.event_subscriber"/>
+        </service>
+
+
     </services>
 </container>

src/Subscriber/PaymentMethodRouteCacheKeySubscriber.php

@@ -0,0 +1,60 @@
+<?php
+declare(strict_types=1);
+
+namespace Kiener\MolliePayments\Subscriber;
+
+use Shopware\Core\Checkout\Cart\SalesChannel\CartService;
+use Shopware\Core\Checkout\Payment\Event\PaymentMethodRouteCacheKeyEvent;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+class PaymentMethodRouteCacheKeySubscriber implements EventSubscriberInterface
+{
+    /**
+     * @var CartService
+     */
+    private $cartService;
+
+    public function __construct(CartService $cartService)
+    {
+        $this->cartService = $cartService;
+    }
+
+    public static function getSubscribedEvents(): array
+    {
+        return [
+            PaymentMethodRouteCacheKeyEvent::class => 'onInvalidateCache'
+        ];
+    }
+
+    /**
+     * shopware caches the payment methods only based on criteria. we add the cart price, currency and billing address id
+     * @param PaymentMethodRouteCacheKeyEvent $event
+     * @return void
+     */
+    public function onInvalidateCache(PaymentMethodRouteCacheKeyEvent $event)
+    {
+        $context = $event->getContext();
+
+        $customer = $context->getCustomer();
+        if ($customer === null) {
+            return;
+        }
+        $billingAddress = $customer->getActiveBillingAddress();
+        $billingAddressId = '';
+        if ($billingAddress !== null) {
+            $billingAddressId = $billingAddress->getId();
+        }
+
+        $cart = $this->cartService->getCart($context->getToken(), $context);
+
+        $cacheParts = $event->getParts();
+
+        $cacheParts[] = md5(implode([
+            $cart->getPrice()->getTotalPrice(),
+            $context->getCurrency()->getIsoCode(),
+            $billingAddressId
+        ]));
+
+        $event->setParts($cacheParts);
+    }
+}