Error getting order item discounts applied_to for customer order via GraphQl customer request

Author: rogerdz

app/code/Magento/SalesGraphQl/Model/OrderItem/DataProvider.php

@@ -10,11 +10,13 @@
 use Magento\Catalog\Api\Data\ProductInterface;
 use Magento\Catalog\Api\ProductRepositoryInterface;
 use Magento\Framework\Api\SearchCriteriaBuilder;
+use Magento\Framework\App\ObjectManager;
 use Magento\Sales\Api\Data\OrderInterface;
 use Magento\Sales\Api\Data\OrderItemInterface;
 use Magento\Sales\Api\OrderItemRepositoryInterface;
 use Magento\Sales\Api\OrderRepositoryInterface;
-use Magento\Framework\App\ObjectManager;
+use Magento\SalesRule\Api\Data\DiscountAppliedToInterface as DiscountAppliedTo;
+
 use Magento\Tax\Helper\Data as TaxHelper;
 
 /**
@@ -240,6 +242,7 @@ private function getDiscountDetails(OrderInterface $associatedOrder, OrderItemIn
         } else {
             $discounts [] = [
                 'label' => $associatedOrder->getDiscountDescription() ?? __('Discount'),
+                'applied_to' => $this->getAppliedTo($associatedOrder),
                 'amount' => [
                     'value' => abs((float) $orderItem->getDiscountAmount()),
                     'currency' => $associatedOrder->getOrderCurrencyCode()
@@ -248,4 +251,18 @@ private function getDiscountDetails(OrderInterface $associatedOrder, OrderItemIn
         }
         return $discounts;
     }
+
+    /**
+     * Get entity type the discount is applied to
+     *
+     * @param OrderInterface $order
+     * @return string
+     */
+    public function getAppliedTo($order)
+    {
+        if ((float) $order->getShippingDiscountAmount() > 0) {
+            return DiscountAppliedTo::APPLIED_TO_SHIPPING;
+        }
+        return DiscountAppliedTo::APPLIED_TO_ITEM;
+    }
 }