MC-23904: Can't Refund Invoice Without 0 Quantities Through REST API

Author: engcom-Echo

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

@@ -96,7 +96,7 @@ public function validate($entity)
 
         if ($entity->getGrandTotal() <= 0) {
             $messages[] = __('The credit memo\'s total must be positive.');
-        } elseif ($totalQuantity <= 0 && !$this->canRefundShipping($order)) {
+        } elseif ($totalQuantity < 0 && !$this->canRefundShipping($order)) {
             $messages[] = __('You can\'t create a creditmemo without products.');
         }
 

app/code/Magento/Sales/Test/Unit/Model/Order/Creditmemo/Validation/QuantityValidatorTest.php

@@ -229,6 +229,15 @@ public function dataProviderForValidateQty()
                 'total' => 15,
                 'expected' => []
             ],
+            [
+                'orderId' => 1,
+                'orderItemId' => 1,
+                'qtyToRequest' => 0,
+                'qtyToRefund' => 0,
+                'sku',
+                'total' => 15,
+                'expected' => []
+            ],
             [
                 'orderId' => 1,
                 'orderItemId' => 1,