ENGCOM-4135: [256] Fixed variant collection #331

 - Merge Pull Request magento/graphql-ce#331 from magento/graphql-ce:256_configurable_products_variants_attributes_are_empty
 - Merged commits:
   1. 9bee85b
   2. e22d32d
   3. 23c9822
   4. cda1eff

Author: magento-engcom-team

app/code/Magento/ConfigurableProductGraphQl/Model/Resolver/ConfigurableVariant.php

@@ -85,7 +85,7 @@ public function resolve(Field $field, $context, ResolveInfo $info, array $value
             return $this->valueFactory->create($result);
         }
 
-        $this->variantCollection->addParentId((int)$value[$linkField]);
+        $this->variantCollection->addParentProduct($value['model']);
         $fields = $this->getProductFields($info);
         $matchedFields = $this->attributeCollection->getRequestAttributes($fields);
         $this->variantCollection->addEavAttributes($matchedFields);

app/code/Magento/ConfigurableProductGraphQl/Model/Resolver/Variant/Attributes.php

@@ -35,12 +35,12 @@ public function resolve(
         $data = [];
         foreach ($value['options'] as $option) {
             $code = $option['attribute_code'];
-            if (!isset($value['product'][$code])) {
+            if (!isset($value['product']['model'][$code])) {
                 continue;
             }
 
             foreach ($option['values'] as $optionValue) {
-                if ($optionValue['value_index'] != $value['product'][$code]) {
+                if ($optionValue['value_index'] != $value['product']['model'][$code]) {
                     continue;
                 }
                 $data[] = [

app/code/Magento/ConfigurableProductGraphQl/Model/Variant/Collection.php

@@ -9,9 +9,9 @@
 
 use Magento\Catalog\Api\Data\ProductInterface;
 use Magento\Catalog\Model\Product;
-use Magento\ConfigurableProduct\Model\ResourceModel\Product\Type\Configurable\Product\CollectionFactory;
-use Magento\ConfigurableProduct\Model\ResourceModel\Product\Type\Configurable\Product\Collection as ChildCollection;
 use Magento\Catalog\Model\ProductFactory;
+use Magento\ConfigurableProduct\Model\ResourceModel\Product\Type\Configurable\Product\Collection as ChildCollection;
+use Magento\ConfigurableProduct\Model\ResourceModel\Product\Type\Configurable\Product\CollectionFactory;
 use Magento\Framework\EntityManager\MetadataPool;
 use Magento\Framework\Api\SearchCriteriaBuilder;
 use Magento\CatalogGraphQl\Model\Resolver\Products\DataProvider\Product as DataProvider;
@@ -47,9 +47,9 @@ class Collection
     private $metadataPool;
 
     /**
-     * @var int[]
+     * @var Product[]
      */
-    private $parentIds = [];
+    private $parentProducts = [];
 
     /**
      * @var array
@@ -83,19 +83,22 @@ public function __construct(
     }
 
     /**
-     * Add parent Id to collection filter
+     * Add parent to collection filter
      *
-     * @param int $id
+     * @param Product $product
      * @return void
      */
-    public function addParentId(int $id) : void
+    public function addParentProduct(Product $product) : void
     {
-        if (!in_array($id, $this->parentIds) && !empty($this->childrenMap)) {
+        if (isset($this->parentProducts[$product->getId()])) {
+            return;
+        }
+
+        if (!empty($this->childrenMap)) {
             $this->childrenMap = [];
-            $this->parentIds[] = $id;
-        } elseif (!in_array($id, $this->parentIds)) {
-            $this->parentIds[] = $id;
+
         }
+        $this->parentProducts[$product->getId()] = $product;
     }
 
     /**
@@ -130,20 +133,23 @@ public function getChildProductsByParentId(int $id) : array
      * Fetch all children products from parent id's.
      *
      * @return array
+     * @throws \Exception
      */
     private function fetch() : array
     {
-        if (empty($this->parentIds) || !empty($this->childrenMap)) {
+        if (empty($this->parentProducts) || !empty($this->childrenMap)) {
             return $this->childrenMap;
         }
 
         $linkField = $this->metadataPool->getMetadata(ProductInterface::class)->getLinkField();
-        foreach ($this->parentIds as $id) {
+        foreach ($this->parentProducts as $product) {
+            $attributeData = $this->getAttributesCodes($product);
             /** @var ChildCollection $childCollection */
             $childCollection = $this->childCollectionFactory->create();
+            $childCollection->addAttributeToSelect($attributeData);
+
             /** @var Product $product */
-            $product = $this->productFactory->create();
-            $product->setData($linkField, $id);
+            $product->setData($linkField, $product->getId());
             $childCollection->setProductFilter($product);
 
             /** @var Product $childProduct */
@@ -160,4 +166,24 @@ private function fetch() : array
 
         return $this->childrenMap;
     }
+
+    /**
+     * Get attributes code
+     *
+     * @param \Magento\Catalog\Model\Product $currentProduct
+     * @return array
+     */
+    private function getAttributesCodes(Product $currentProduct): array
+    {
+        $attributeCodes = [];
+        $allowAttributes = $currentProduct->getTypeInstance()->getConfigurableAttributes($currentProduct);
+        foreach ($allowAttributes as $attribute) {
+            $productAttribute = $attribute->getProductAttribute();
+            if (!\in_array($productAttribute->getAttributeCode(), $attributeCodes)) {
+                $attributeCodes[] = $productAttribute->getAttributeCode();
+            }
+        }
+
+        return $attributeCodes;
+    }
 }

dev/tests/api-functional/testsuite/Magento/GraphQl/ConfigurableProduct/ConfigurableProductViewTest.php

@@ -407,6 +407,7 @@ private function assertConfigurableVariants($actualResponse)
                 $variantArray['product']['price']
             );
             $configurableOptions = $this->getConfigurableOptions();
+            $this->assertEquals(1, count($variantArray['attributes']));
             foreach ($variantArray['attributes'] as $attribute) {
                 $hasAssertion = false;
                 foreach ($configurableOptions as $option) {