WIP: GetCustomAttributeCodes service

Author: schmengler

app/code/Magento/Eav/Model/Entity/GetCustomAttributeCodes.php

@@ -0,0 +1,63 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Eav\Model\Entity;
+
+
+use Magento\Framework\Api\MetadataServiceInterface;
+
+class GetCustomAttributeCodes
+{
+    /**
+     * @var string[]
+     */
+    private $customAttributesCodes;
+
+    /**
+     * Receive a list of custom EAV attributes using provided metadata service. The results are cached per entity type
+     *
+     * @param MetadataServiceInterface $metadataService Custom attribute metadata service to be used
+     * @param string[] $interfaceAttributes Attribute codes that are part of the interface and should not be
+     *                                      considered custom
+     * @param string|null $entityType Entity type (class name), only needed if metadata service handles different
+     *                                entities
+     * @return string[]
+     */
+    public function execute(
+        MetadataServiceInterface $metadataService,
+        array $interfaceAttributes,
+        string $entityType = null
+    ): array {
+        $cacheKey = get_class($metadataService) . '|' . $entityType;
+        if (!isset($this->customAttributesCodes[$cacheKey])) {
+            $customAttributesCodes = $this->getEavAttributesCodes($metadataService, $entityType);
+            $this->customAttributesCodes[$cacheKey] = array_values(
+                array_diff($customAttributesCodes, $interfaceAttributes)
+            );
+        }
+        return $this->customAttributesCodes;
+    }
+
+    /**
+     * Receive a list of EAV attributes using provided metadata service.
+     *
+     * @param MetadataServiceInterface $metadataService
+     * @param string|null $entityType
+     * @return string[]
+     */
+    private function getEavAttributesCodes(MetadataServiceInterface $metadataService, string $entityType = null)
+    {
+        $attributeCodes = [];
+        $customAttributesMetadata = $metadataService->getCustomAttributesMetadata($entityType);
+        if (is_array($customAttributesMetadata)) {
+            /** @var $attribute \Magento\Framework\Api\MetadataObjectInterface */
+            foreach ($customAttributesMetadata as $attribute) {
+                $attributeCodes[] = $attribute->getAttributeCode();
+            }
+        }
+        return $attributeCodes;
+    }
+}