magento/magento2#39873: addProductsToCart mutation doesn't work as expect with a given parent_sku

app/code/Magento/QuoteGraphQl/Model/CartItem/Precursor/ConfigurableProductPrecursor.php

@@ -0,0 +1,146 @@
+<?php
+/**
+ * Copyright 2025 Adobe
+ * All Rights Reserved.
+ */
+declare(strict_types=1);
+
+namespace Magento\QuoteGraphQl\Model\CartItem\Precursor;
+
+use Magento\Catalog\Api\Data\ProductInterface;
+use Magento\Catalog\Api\ProductRepositoryInterface;
+use Magento\ConfigurableProduct\Model\Product\Type\Configurable;
+use Magento\Framework\Exception\NoSuchEntityException;
+use Magento\GraphQl\Model\Query\ContextInterface;
+use Magento\QuoteGraphQl\Model\CartItem\PrecursorInterface;
+
+/**
+ * Handles parent-child relationship for configurable products
+ */
+class ConfigurableProductPrecursor implements PrecursorInterface
+{
+    /**
+     * @var array
+     */
+    private array $errors = [];
+
+    /**
+     * @var ProductRepositoryInterface
+     */
+    private ProductRepositoryInterface $productRepository;
+
+    /**
+     * @param ProductRepositoryInterface $productRepository
+     */
+    public function __construct(
+        ProductRepositoryInterface $productRepository
+    ) {
+        $this->productRepository = $productRepository;
+    }
+
+    /**
+     * Process cart item data to handle parent_sku for configurable products
+     *
+     * @param array $cartItemData
+     * @param ContextInterface $context
+     * @return array
+     */
+    public function process(array $cartItemData, ContextInterface $context): array
+    {
+        $processedCartItemData = [];
+
+        foreach ($cartItemData as $cartItemIndex => $cartItem) {
+            if (!isset($cartItem['parent_sku'])) {
+                $processedCartItemData[$cartItemIndex] = $cartItem;
+                continue;
+            }
+
+            try {
+                $childProduct = $this->productRepository->get($cartItem['sku']);
+                $parentProduct = $this->productRepository->get($cartItem['parent_sku']);
+
+                if ($parentProduct->getTypeId() !== Configurable::TYPE_CODE) {
+                    $this->errors[] = [
+                        'message' => sprintf('Product %s is not a configurable product', $cartItem['parent_sku']),
+                        'code' => 'UNDEFINED'
+                    ];
+                    $processedCartItemData[$cartItemIndex] = $cartItem;
+                    continue;
+                }
+
+                $configurableOptions = $this->getConfigurableOptions($parentProduct, $childProduct);
+
+                if (empty($configurableOptions)) {
+                    $this->errors[] = [
+                        'message' => sprintf('Could not match child product %s with parent %s', $cartItem['sku'], $cartItem['parent_sku']),
+                        'code' => 'UNDEFINED'
+                    ];
+                    $processedCartItemData[$cartItemIndex] = $cartItem;
+                    continue;
+                }
+
+                $parentCartItem = [
+                    'sku' => $cartItem['parent_sku'],
+                    'quantity' => $cartItem['quantity'],
+                    'selected_options' => array_merge($configurableOptions, $cartItem['selected_options'] ?? []),
+                    'entered_options' => $cartItem['entered_options'] ?? [],
+                    'parent_sku' => null
+                ];
+
+                $processedCartItemData[] = $parentCartItem;
+                unset($cartItemData[$cartItemIndex]);
+
+            } catch (NoSuchEntityException $e) {
+                $this->errors[] = [
+                    'message' => $e->getMessage(),
+                    'code' => 'UNDEFINED'
+                ];
+                $processedCartItemData[$cartItemIndex] = $cartItem;
+            }
+        }
+
+        return $processedCartItemData;
+    }
+
+    /**
+     * Get configurable option IDs for the simple product
+     *
+     * @param ProductInterface $parentProduct
+     * @param ProductInterface $childProduct
+     * @return array
+     */
+    private function getConfigurableOptions(ProductInterface $parentProduct, ProductInterface $childProduct): array
+    {
+        $selectedOptions = [];
+
+        /** @var Configurable $configurableType */
+        $configurableType = $parentProduct->getTypeInstance();
+        $attributes = $configurableType->getConfigurableAttributes($parentProduct);
+
+        $childProductData = $childProduct->getData();
+
+        foreach ($attributes as $attribute) {
+            $attributeId = $attribute->getProductAttribute()->getAttributeId();
+            $attributeCode = $attribute->getProductAttribute()->getAttributeCode();
+
+            if (!isset($childProductData[$attributeCode])) {
+                continue;
+            }
+
+            $optionId = $childProductData[$attributeCode];
+            $selectedOptions[] = base64_encode("configurable/$attributeId/$optionId");
+        }
+
+        return $selectedOptions;
+    }
+
+    /**
+     * Return collected errors
+     *
+     * @return array
+     */
+    public function getErrors(): array
+    {
+        return $this->errors;
+    }
+}

app/code/Magento/QuoteGraphQl/etc/graphql/di.xml

@@ -106,4 +106,11 @@
             </argument>
         </arguments>
     </type>
+    <type name="Magento\QuoteGraphQl\Model\CartItem\PrecursorComposite">
+        <arguments>
+            <argument name="precursors" xsi:type="array">
+                <item name="configurableProductPrecursor" xsi:type="object">Magento\QuoteGraphQl\Model\CartItem\Precursor\ConfigurableProductPrecursor</item>
+            </argument>
+        </arguments>
+    </type>
 </config>