MAGETWO-94565: Catalog product collection filters produce errors and cause inconsistent behaviour

- Fix CR comments.

Author: YuliyaLabudova

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

@@ -1155,6 +1155,10 @@ public function getCategoryWithChildren(int $categoryId): array
             )->where('entity_type_id = ?', CategorySetup::CATEGORY_ENTITY_TYPE_ID)
             ->where('attribute_code = ?', 'is_anchor')
             ->limit(1);
+        $isAnchorAttributeCode = $connection->fetchOne($selectAttributeCode);
+        if (empty($isAnchorAttributeCode) || (int)$isAnchorAttributeCode <= 0) {
+            return [];
+        }
 
         $select = $connection->select()
             ->from(
@@ -1166,7 +1170,7 @@ public function getCategoryWithChildren(int $categoryId): array
                 ['is_anchor' => 'cce_int.value']
             )->where(
                 'cce_int.attribute_id = ?',
-                $connection->fetchOne($selectAttributeCode)
+                $isAnchorAttributeCode
             )->where(
                 "cce.path LIKE '%/{$categoryId}' OR cce.path LIKE '%/{$categoryId}/%'"
             )->order('path');

app/code/Magento/Catalog/Model/ResourceModel/Product/Collection.php

@@ -2107,6 +2107,10 @@ private function getChildrenCategories(int $categoryId): array
         $anchorCategory = [];
 
         $categories = $this->categoryResourceModel->getCategoryWithChildren($categoryId);
+        if (empty($categories)) {
+            return $categoryIds;
+        }
+
         $firstCategory = array_shift($categories);
         if ($firstCategory['is_anchor'] == 1) {
             $anchorCategory[] = (int)$firstCategory['entity_id'];

dev/tests/integration/testsuite/Magento/Catalog/Model/ResourceModel/Product/CollectionTest.php

@@ -99,6 +99,7 @@ public function testAddPriceDataOnSchedule()
 
     /**
      * @magentoDataFixture Magento/Catalog/_files/products.php
+     * @magentoAppIsolation enabled
      * @magentoDbIsolation disabled
      */
     public function testSetVisibility()
@@ -116,6 +117,7 @@ public function testSetVisibility()
 
     /**
      * @magentoDataFixture Magento/Catalog/_files/category_product.php
+     * @magentoAppIsolation enabled
      * @magentoDbIsolation disabled
      */
     public function testSetCategoryWithStoreFilter()
@@ -131,8 +133,8 @@ public function testSetCategoryWithStoreFilter()
         $this->collection->load();
 
         $collectionStoreFilterAfter = Bootstrap::getObjectManager()->create(
-            \Magento\Catalog\Model\ResourceModel\Product\Collection::class
-        );
+            \Magento\Catalog\Model\ResourceModel\Product\CollectionFactory::class
+        )->create();
         $collectionStoreFilterAfter->addStoreFilter(1)->addCategoryFilter($category);
         $collectionStoreFilterAfter->load();
         $this->assertEquals($this->collection->getItems(), $collectionStoreFilterAfter->getItems());
@@ -141,6 +143,7 @@ public function testSetCategoryWithStoreFilter()
 
     /**
      * @magentoDataFixture Magento/Catalog/_files/categories.php
+     * @magentoAppIsolation enabled
      * @magentoDbIsolation disabled
      */
     public function testSetCategoryFilter()