improve fix

Author: engcom-Charlie

app/code/Magento/Newsletter/Model/Plugin/CustomerPlugin.php

@@ -17,6 +17,7 @@
 use Magento\Newsletter\Model\SubscriptionManagerInterface;
 use Magento\Store\Model\Store;
 use Magento\Store\Model\StoreManagerInterface;
+use Magento\Framework\Api\SearchResults;
 use Psr\Log\LoggerInterface;
 
 /**
@@ -229,6 +230,27 @@ public function afterGetById(CustomerRepositoryInterface $subject, CustomerInter
         return $customer;
     }
 
+    /**
+     * Add subscription status to customer list
+     *
+     * @param CustomerRepositoryInterface $subject
+     * @param SearchResults $searchResults
+     * @return SearchResults
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function afterGetList(CustomerRepositoryInterface $subject, SearchResults $searchResults): SearchResults
+    {
+        foreach ($searchResults->getItems() as $customer) {
+            /** @var CustomerExtensionInterface $extensionAttributes */
+            $extensionAttributes = $customer->getExtensionAttributes();
+
+            $isSubscribed = (int) $extensionAttributes->getIsSubscribed() === Subscriber::STATUS_SUBSCRIBED ?: false;
+            $extensionAttributes->setIsSubscribed($isSubscribed);
+        }
+
+        return $searchResults;
+    }
+
     /**
      * Set Is Subscribed extension attribute
      *

app/code/Magento/Newsletter/etc/extension_attributes.xml

@@ -8,6 +8,10 @@
 
 <config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Api/etc/extension_attributes.xsd">
     <extension_attributes for="Magento\Customer\Api\Data\CustomerInterface">
-        <attribute code="is_subscribed" type="boolean" />
+        <attribute code="is_subscribed" type="boolean" >
+            <join reference_table="newsletter_subscriber" reference_field="customer_id" join_on_field="entity_id">
+                <field>subscriber_status</field>
+            </join>
+        </attribute>
     </extension_attributes>
 </config>