Final fix

src/Resources/config/services/subscriber.xml

@@ -42,6 +42,7 @@
 
         <service id="Kiener\MolliePayments\Subscriber\StorefrontBuildSubscriber">
             <argument type="service" id="Kiener\MolliePayments\Service\SettingsService"/>
+            <argument type="service" id="Shopware\Storefront\Theme\StorefrontPluginRegistry"/>
             <argument>%kernel.shopware_version%</argument>
             <tag name="kernel.event_subscriber"/>
         </service>

src/Resources/views/mollie/head.html.twig

@@ -9,7 +9,6 @@
         'frontend.detail.page' : 'pdp'
     } %}
 
-
     {% set currentRoute = app.request.attributes.get('_route') %}
     {% set includeJsInHeader = false %}
 
@@ -28,19 +27,11 @@
         {% endif %}
     {% endif %}
 
-    {% if includeJsInHeader == true and mollie_javascript_use_head == true %}
-        {% for script in theme_scripts() %}
-            {% if script == 'js/mollie-payments/mollie-payments.js' %}
-                {% set includeJsInHeader = false %}
-            {% endif %}
-        {% endfor %}
-    {% endif %}
-
     <script>
         window.mollie_javascript_use_shopware = '{{ mollie_javascript_use_shopware }}'
     </script>
 
-    {% if mollie_javascript_use_shopware != '1' and includeJsInHeader == true %}
+    {% if mollie_javascript_already_exists == false and mollie_javascript_use_shopware != '1' and includeJsInHeader == true %}
         <script type="text/javascript" src="{{ asset('bundles/molliepayments/mollie-payments.js', 'asset') }}" defer></script>
     {% endif %}
 

src/Subscriber/StorefrontBuildSubscriber.php

@@ -5,6 +5,7 @@
 use Kiener\MolliePayments\Compatibility\VersionCompare;
 use Kiener\MolliePayments\Service\SettingsService;
 use Shopware\Storefront\Event\StorefrontRenderEvent;
+use Shopware\Storefront\Theme\StorefrontPluginRegistryInterface;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
 class StorefrontBuildSubscriber implements EventSubscriberInterface
@@ -14,6 +15,11 @@ class StorefrontBuildSubscriber implements EventSubscriberInterface
      */
     private $settingsService;
 
+    /**
+     * @var StorefrontPluginRegistryInterface
+     */
+    private $pluginRegistry;
+
     /**
      * @var VersionCompare
      */
@@ -24,9 +30,10 @@ class StorefrontBuildSubscriber implements EventSubscriberInterface
      * @param SettingsService $settingsService
      * @param string $shopwareVersion
      */
-    public function __construct(SettingsService $settingsService, string $shopwareVersion)
+    public function __construct(SettingsService $settingsService, StorefrontPluginRegistryInterface $pluginRegistry, string $shopwareVersion)
     {
         $this->settingsService = $settingsService;
+        $this->pluginRegistry = $pluginRegistry;
         $this->versionCompare = new VersionCompare($shopwareVersion);
     }
 
@@ -51,6 +58,12 @@ public function onStorefrontRender(StorefrontRenderEvent $event): void
 
         $useJsValue = (int)$settings->isUseShopwareJavascript();
         $event->setParameter('mollie_javascript_use_shopware', $useJsValue);
-        $event->setParameter('mollie_javascript_use_head', $this->versionCompare->gte('6.6'));
+
+        $mollieJavascriptAlreadyExists = false;
+        if($this->versionCompare->gte('6.6')) {
+            $molliePayments = $this->pluginRegistry->getConfigurations()->getByTechnicalName('MolliePayments');
+            $mollieJavascriptAlreadyExists = $molliePayments?->getScriptFiles()->count() ?? 0 > 0;
+        }
+        $event->setParameter('mollie_javascript_already_exists', $mollieJavascriptAlreadyExists);
     }
 }