Issue #3128594 by tcrawford, Berdir: Duplicate check failing on processPayment

src/Plugin/Commerce/PaymentGateway/Datatrans.php

@@ -348,7 +348,7 @@ class Datatrans extends OffsitePaymentGatewayBase {
   protected function processPayment(array $post_data, OrderInterface $order) {
     $payment_storage = $this->entityTypeManager->getStorage('commerce_payment');
 
-    if ($payment_storage->loadByProperties(['remote_id' => $post_data['authorizationCode']])) {
+    if ($payment_storage->loadByProperties(['remote_id' => $post_data['uppTransactionId']])) {
       return FALSE;
     }
 

tests/src/Kernel/DatatransKernelTest.php

@@ -113,6 +113,9 @@ class DatatransKernelTest extends CommerceKernelTestBase {
     ]);
     $datatrans->onReturn($this->order, $request);
 
+    // Process a second time, ensure that no duplicate is created.
+    $datatrans->onReturn($this->order, $request);
+
     $payments = $this->entityTypeManager->getStorage('commerce_payment')->loadMultiple(NULL);
     $this->assertCount(1, $payments);