MAGETWO-98522: Adding out of stock items to comparison shows success message but fails

- Delete button if product is not available for comparison.

Author: YuliyaLabudova

app/code/Magento/Catalog/ViewModel/Product/Checker/AddToCompareAvailability.php

@@ -0,0 +1,59 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Catalog\ViewModel\Product\Checker;
+
+use Magento\Framework\View\Element\Block\ArgumentInterface;
+use Magento\Catalog\Api\Data\ProductInterface;
+use Magento\CatalogInventory\Api\StockConfigurationInterface;
+
+/**
+ * Check is available add to compare.
+ */
+class AddToCompareAvailability implements ArgumentInterface
+{
+    /**
+     * @var StockConfigurationInterface
+     */
+    private $stockConfiguration;
+
+    /**
+     * @param StockConfigurationInterface $stockConfiguration
+     */
+    public function __construct(StockConfigurationInterface $stockConfiguration)
+    {
+        $this->stockConfiguration = $stockConfiguration;
+    }
+
+    /**
+     * Is product available for comparison.
+     *
+     * @return bool
+     */
+    public function isAvailableForCompare(ProductInterface $product): bool
+    {
+        return $this->isInStock($product) ||
+            !$this->isInStock($product) && $this->stockConfiguration->isShowOutOfStock();
+    }
+
+    /**
+     * Get is in stock status.
+     *
+     * @return bool
+     */
+    private function isInStock(ProductInterface $product): bool
+    {
+        $quantityAndStockStatus = $product->getQuantityAndStockStatus();
+        if (!$quantityAndStockStatus) {
+            return $product->isSalable();
+        }
+
+        return isset($quantityAndStockStatus['is_in_stock'])
+            ? $quantityAndStockStatus['is_in_stock']
+            : false;
+    }
+}

app/code/Magento/Catalog/view/frontend/layout/catalog_product_view.xml

@@ -91,7 +91,11 @@
                     <container name="product.info.social" label="Product social links container" htmlTag="div" htmlClass="product-social-links">
                         <block class="Magento\Catalog\Block\Product\View" name="product.info.addto" as="addto" template="Magento_Catalog::product/view/addto.phtml">
                             <block class="Magento\Catalog\Block\Product\View\AddTo\Compare" name="view.addto.compare" after="view.addto.wishlist"
-                                   template="Magento_Catalog::product/view/addto/compare.phtml" />
+                                   template="Magento_Catalog::product/view/addto/compare.phtml" >
+                                <arguments>
+                                    <argument name="addToCompareViewModel" xsi:type="object">Magento\Catalog\ViewModel\Product\Checker\AddToCompareAvailability</argument>
+                                </arguments>
+                            </block>
                         </block>
                         <block class="Magento\Catalog\Block\Product\View" name="product.info.mailto" template="Magento_Catalog::product/view/mailto.phtml"/>
                     </container>

app/code/Magento/Catalog/view/frontend/templates/product/view/addto/compare.phtml

@@ -9,6 +9,10 @@
 /** @var $block \Magento\Catalog\Block\Product\View\Addto\Compare */
 ?>
 
+<?php $viewModel = $block->getData('addToCompareViewModel'); ?>
+<?php if ($viewModel->isAvailableForCompare($block->getProduct())): ?>
 <a href="#" data-post='<?= /* @escapeNotVerified */ $block->getPostDataParams() ?>'
         data-role="add-to-links"
         class="action tocompare"><span><?= /* @escapeNotVerified */ __('Add to Compare') ?></span></a>
+<?php endif; ?>
+