save invoice ID on credit memo when using API method salesRefundInvoiceV1

app/code/Magento/Sales/Model/Order/Creditmemo.php

@@ -9,8 +9,10 @@
 namespace Magento\Sales\Model\Order;
 
 use Magento\Framework\Api\AttributeValueFactory;
+use Magento\Framework\App\ObjectManager;
 use Magento\Framework\Pricing\PriceCurrencyInterface;
 use Magento\Sales\Api\Data\CreditmemoInterface;
+use Magento\Sales\Api\InvoiceRepositoryInterface;
 use Magento\Sales\Model\AbstractModel;
 use Magento\Sales\Model\EntityInterface;
 
@@ -114,6 +116,11 @@ class Creditmemo extends AbstractModel implements EntityInterface, CreditmemoInt
      */
     protected $priceCurrency;
 
+    /**
+     * @var InvoiceRepository
+     */
+    private $invoiceRepository;
+
     /**
      * @param \Magento\Framework\Model\Context $context
      * @param \Magento\Framework\Registry $registry
@@ -130,6 +137,7 @@ class Creditmemo extends AbstractModel implements EntityInterface, CreditmemoInt
      * @param \Magento\Framework\Model\ResourceModel\AbstractResource $resource
      * @param \Magento\Framework\Data\Collection\AbstractDb $resourceCollection
      * @param array $data
+     * @param InvoiceRepository $invoiceRepository
      * @SuppressWarnings(PHPMD.ExcessiveParameterList)
      */
     public function __construct(
@@ -147,7 +155,8 @@ public function __construct(
         PriceCurrencyInterface $priceCurrency,
         \Magento\Framework\Model\ResourceModel\AbstractResource $resource = null,
         \Magento\Framework\Data\Collection\AbstractDb $resourceCollection = null,
-        array $data = []
+        array $data = [],
+        InvoiceRepository $invoiceRepository = null
     ) {
         $this->_creditmemoConfig = $creditmemoConfig;
         $this->_orderFactory = $orderFactory;
@@ -157,6 +166,7 @@ public function __construct(
         $this->_commentFactory = $commentFactory;
         $this->_commentCollectionFactory = $commentCollectionFactory;
         $this->priceCurrency = $priceCurrency;
+        $this->invoiceRepository = $invoiceRepository;
         parent::__construct(
             $context,
             $registry,
@@ -379,6 +389,9 @@ public function canRefund()
      */
     public function getInvoice()
     {
+        if (!$this->getData('invoice') instanceof \Magento\Sales\Model\Order\Invoice && $this->getInvoiceId()) {
+            $this->setInvoice($this->getInvoiceRepository()->get($this->getInvoiceId()));
+        }
         return $this->getData('invoice');
     }
 
@@ -391,6 +404,7 @@ public function getInvoice()
     public function setInvoice(Invoice $invoice)
     {
         $this->setData('invoice', $invoice);
+        $this->setInvoiceId($invoice->getId());
         return $this;
     }
 
@@ -1525,5 +1539,12 @@ public function setExtensionAttributes(\Magento\Sales\Api\Data\CreditmemoExtensi
         return $this->_setExtensionAttributes($extensionAttributes);
     }
 
+    /**
+     * @return InvoiceRepositoryInterface|mixed
+     * @deprecated
+     */
+    private function getInvoiceRepository() {
+        return $this->invoiceRepository ?: ObjectManager::getInstance()->get(InvoiceRepositoryInterface::class);
+    }
     //@codeCoverageIgnoreEnd
 }