MAGETWO-91437: Invalidate indexer after category is deleted

 - Write plugin to invalidate fulltext
 - Invalidate category_product on after delete for Category resource model
 - Write integration tests

Author: eric-bohanon

app/code/Magento/Catalog/Model/ResourceModel/Category.php

@@ -11,6 +11,8 @@
  */
 namespace Magento\Catalog\Model\ResourceModel;
 
+use Magento\Catalog\Model\Indexer\Category\Product\Processor;
+use Magento\Framework\DataObject;
 use Magento\Framework\EntityManager\EntityManager;
 
 /**
@@ -82,6 +84,11 @@ class Category extends AbstractResource
      */
     protected $aggregateCount;
 
+    /**
+     * @var Processor
+     */
+    private $indexerProcessor;
+
     /**
      * Category constructor.
      * @param \Magento\Eav\Model\Entity\Context $context
@@ -90,6 +97,7 @@ class Category extends AbstractResource
      * @param \Magento\Framework\Event\ManagerInterface $eventManager
      * @param Category\TreeFactory $categoryTreeFactory
      * @param Category\CollectionFactory $categoryCollectionFactory
+     * @param Processor $indexerProcessor
      * @param array $data
      * @param \Magento\Framework\Serialize\Serializer\Json|null $serializer
      */
@@ -100,6 +108,7 @@ public function __construct(
         \Magento\Framework\Event\ManagerInterface $eventManager,
         \Magento\Catalog\Model\ResourceModel\Category\TreeFactory $categoryTreeFactory,
         \Magento\Catalog\Model\ResourceModel\Category\CollectionFactory $categoryCollectionFactory,
+        Processor $indexerProcessor,
         $data = [],
         \Magento\Framework\Serialize\Serializer\Json $serializer = null
     ) {
@@ -113,6 +122,7 @@ public function __construct(
         $this->_categoryCollectionFactory = $categoryCollectionFactory;
         $this->_eventManager = $eventManager;
         $this->connectionName  = 'catalog';
+        $this->indexerProcessor = $indexerProcessor;
         $this->serializer = $serializer ?: \Magento\Framework\App\ObjectManager::getInstance()
             ->get(\Magento\Framework\Serialize\Serializer\Json::class);
     }
@@ -197,6 +207,19 @@ protected function _beforeDelete(\Magento\Framework\DataObject $object)
         $this->deleteChildren($object);
     }
 
+    /**
+     * Mark Category indexer as invalid to be picked up by cron.
+     *
+     * @param DataObject $object
+     * @return $this
+     */
+    protected function _afterDelete(DataObject $object)
+    {
+        $this->indexerProcessor->markIndexerAsInvalid();
+        return parent::_afterDelete($object);
+    }
+
+
     /**
      * Delete children categories of specific category
      *

app/code/Magento/CatalogSearch/Model/Indexer/Fulltext/Model/Plugin/Category.php

@@ -0,0 +1,45 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\CatalogSearch\Model\Indexer\Fulltext\Model\Plugin;
+
+use Magento\Catalog\Model\ResourceModel\Category as Resource;
+use Magento\CatalogSearch\Model\Indexer\Fulltext\Processor;
+
+/**
+ * Perform indexer invalidation after a category delete.
+ */
+class Category
+{
+    /**
+     * @var Processor
+     */
+    private $fulltextIndexerProcessor;
+
+    /**
+     * @param Processor $fulltextIndexerProcessor
+     */
+    public function __construct(Processor $fulltextIndexerProcessor)
+    {
+        $this->fulltextIndexerProcessor = $fulltextIndexerProcessor;
+    }
+
+    /**
+     * Mark fulltext indexer as invalid post-deletion of category.
+     *
+     * @param Resource $subjectCategory
+     * @param Resource $resultCategory
+     * @return Resource
+     * @SuppressWarnings(PHPMD.UnusedFormalParameter)
+     */
+    public function afterDelete(Resource $subjectCategory, Resource $resultCategory) : Resource
+    {
+        $this->fulltextIndexerProcessor->markIndexerAsInvalid();
+
+        return $resultCategory;
+    }
+}

app/code/Magento/CatalogSearch/etc/adminhtml/di.xml

@@ -31,4 +31,7 @@
             <argument name="filter" xsi:type="object">Magento\CatalogSearch\Ui\DataProvider\Product\AddFulltextFilterToCollection</argument>
         </arguments>
     </type>
+    <type name="Magento\Catalog\Model\ResourceModel\Category">
+        <plugin name="fulltext_search_indexer" type="Magento\CatalogSearch\Model\Indexer\Fulltext\Model\Plugin\Category"/>
+    </type>
 </config>

app/code/Magento/CatalogSearch/etc/webapi_rest/di.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<!--
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
+    <type name="Magento\Catalog\Model\ResourceModel\Category">
+        <plugin name="fulltext_search_indexer" type="Magento\CatalogSearch\Model\Indexer\Fulltext\Model\Plugin\Category"/>
+    </type>
+</config>

app/code/Magento/CatalogSearch/etc/webapi_soap/di.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0"?>
+<!--
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+-->
+<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
+    <type name="Magento\Catalog\Model\ResourceModel\Category">
+        <plugin name="fulltext_search_indexer" type="Magento\CatalogSearch\Model\Indexer\Fulltext\Model\Plugin\Category"/>
+    </type>
+</config>