MC-21811: Canonical_url displays the backend domain instead of relative

- add category implementation

Author: cpartica

app/code/Magento/CatalogGraphQl/Model/Resolver/Category/CanonicalUrl.php

@@ -0,0 +1,58 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\CatalogGraphQl\Model\Resolver\Category;
+
+use Magento\Catalog\Model\Category;
+use Magento\Framework\Exception\LocalizedException;
+use Magento\Framework\GraphQl\Config\Element\Field;
+use Magento\Framework\GraphQl\Query\ResolverInterface;
+use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
+use Magento\Store\Api\Data\StoreInterface;
+use Magento\Catalog\Helper\Category as CategoryHelper;
+
+/**
+ * Resolve data for category canonical URL
+ */
+class CanonicalUrl implements ResolverInterface
+{
+    /** @var CategoryHelper */
+    private $categoryHelper;
+
+    /**
+     * CanonicalUrl constructor.
+     * @param CategoryHelper $categoryHelper
+     */
+    public function __construct(CategoryHelper $categoryHelper)
+    {
+        $this->categoryHelper = $categoryHelper;
+    }
+
+    /**
+     * @inheritdoc
+     */
+    public function resolve(
+        Field $field,
+        $context,
+        ResolveInfo $info,
+        array $value = null,
+        array $args = null
+    ) {
+        if (!isset($value['model'])) {
+            throw new LocalizedException(__('"model" value should be specified'));
+        }
+
+        /* @var Category $category */
+        $category = $value['model'];
+        /** @var StoreInterface $store */
+        $store = $context->getExtensionAttributes()->getStore();
+        if ($this->categoryHelper->canUseCanonicalTag($store)) {
+            $baseUrl = $category->getUrlInstance()->getBaseUrl();
+            return str_replace($baseUrl, '', $category->getUrl());
+        }
+    }
+}

app/code/Magento/CatalogGraphQl/Model/Resolver/Product/CanonicalUrl.php

@@ -45,7 +45,7 @@ public function resolve(
             throw new LocalizedException(__('"model" value should be specified'));
         }
 
-        /* @var $product Product */
+        /* @var Product $product */
         $product = $value['model'];
         /** @var StoreInterface $store */
         $store = $context->getExtensionAttributes()->getStore();

app/code/Magento/CatalogGraphQl/etc/schema.graphqls

@@ -109,7 +109,7 @@ interface ProductInterface @typeResolver(class: "Magento\\CatalogGraphQl\\Model\
     gift_message_available: String @doc(description: "Indicates whether a gift message is available.")
     manufacturer: Int @doc(description: "A number representing the product's manufacturer.")
     categories: [CategoryInterface] @doc(description: "The categories assigned to a product.") @resolver(class: "Magento\\CatalogGraphQl\\Model\\Resolver\\Categories") @cache(cacheIdentity: "Magento\\CatalogGraphQl\\Model\\Resolver\\Category\\CategoriesIdentity")
-    canonical_url: String @doc(description: "Canonical URL.") @resolver(class: "Magento\\CatalogGraphQl\\Model\\Resolver\\Product\\CanonicalUrl")
+    canonical_url: String @doc(description: "Relative canonical URL. This value is returned only if the system setting 'Use Canonical Link Meta Tag For Products' is enabled") @resolver(class: "Magento\\CatalogGraphQl\\Model\\Resolver\\Product\\CanonicalUrl")
     media_gallery: [MediaGalleryInterface] @doc(description: "An array of Media Gallery objects.") @resolver(class: "Magento\\CatalogGraphQl\\Model\\Resolver\\Product\\MediaGallery")
 }
 
@@ -223,6 +223,7 @@ interface CategoryInterface @typeResolver(class: "Magento\\CatalogGraphQl\\Model
     path_in_store: String @doc(description: "Category path in store.")
     url_key: String @doc(description: "The url key assigned to the category.")
     url_path: String @doc(description: "The url path assigned to the category.")
+    canonical_url: String @doc(description: "Relative canonical URL. This value is returned only if the system setting 'Use Canonical Link Meta Tag For Categories' is enabled") @resolver(class: "Magento\\CatalogGraphQl\\Model\\Resolver\\Category\\CanonicalUrl")
     position: Int @doc(description: "The position of the category relative to other categories at the same level in tree.")
     level: Int @doc(description: "Indicates the depth of the category within the tree.")
     created_at: String @doc(description: "Timestamp indicating when the category was created.")