ENGCOM-7102: #26749: Saving CMS Page Title from REST web API makes content empty #27237

 - Merge Pull Request #27237 from engcom-Charlie/magento2:24704
 - Merged commits:
   1. f91aff1
   2. e74825a

Author: magento-engcom-team

app/code/Magento/Cms/Model/PageRepository.php

@@ -9,19 +9,21 @@
 use Magento\Cms\Api\Data;
 use Magento\Cms\Api\PageRepositoryInterface;
 use Magento\Cms\Model\Page\IdentityMap;
+use Magento\Cms\Model\ResourceModel\Page as ResourcePage;
+use Magento\Cms\Model\ResourceModel\Page\CollectionFactory as PageCollectionFactory;
 use Magento\Framework\Api\DataObjectHelper;
 use Magento\Framework\Api\SearchCriteria\CollectionProcessorInterface;
 use Magento\Framework\App\ObjectManager;
+use Magento\Framework\EntityManager\HydratorInterface;
 use Magento\Framework\Exception\CouldNotDeleteException;
 use Magento\Framework\Exception\CouldNotSaveException;
 use Magento\Framework\Exception\NoSuchEntityException;
 use Magento\Framework\Reflection\DataObjectProcessor;
-use Magento\Cms\Model\ResourceModel\Page as ResourcePage;
-use Magento\Cms\Model\ResourceModel\Page\CollectionFactory as PageCollectionFactory;
 use Magento\Store\Model\StoreManagerInterface;
 
 /**
- * Class PageRepository
+ * @inheritdoc
+ *
  * @SuppressWarnings(PHPMD.CouplingBetweenObjects)
  */
 class PageRepository implements PageRepositoryInterface
@@ -76,6 +78,11 @@ class PageRepository implements PageRepositoryInterface
      */
     private $identityMap;
 
+    /**
+     * @var HydratorInterface
+     */
+    private $hydrator;
+
     /**
      * @param ResourcePage $resource
      * @param PageFactory $pageFactory
@@ -87,6 +94,7 @@ class PageRepository implements PageRepositoryInterface
      * @param StoreManagerInterface $storeManager
      * @param CollectionProcessorInterface $collectionProcessor
      * @param IdentityMap|null $identityMap
+     * @param HydratorInterface|null $hydrator
      * @SuppressWarnings(PHPMD.ExcessiveParameterList)
      */
     public function __construct(
@@ -99,7 +107,8 @@ public function __construct(
         DataObjectProcessor $dataObjectProcessor,
         StoreManagerInterface $storeManager,
         CollectionProcessorInterface $collectionProcessor = null,
-        ?IdentityMap $identityMap = null
+        ?IdentityMap $identityMap = null,
+        ?HydratorInterface $hydrator = null
     ) {
         $this->resource = $resource;
         $this->pageFactory = $pageFactory;
@@ -111,6 +120,7 @@ public function __construct(
         $this->storeManager = $storeManager;
         $this->collectionProcessor = $collectionProcessor ?: $this->getCollectionProcessor();
         $this->identityMap = $identityMap ?? ObjectManager::getInstance()->get(IdentityMap::class);
+        $this->hydrator = $hydrator ?: ObjectManager::getInstance()->get(HydratorInterface::class);
     }
 
     /**
@@ -150,8 +160,13 @@ public function save(\Magento\Cms\Api\Data\PageInterface $page)
             $storeId = $this->storeManager->getStore()->getId();
             $page->setStoreId($storeId);
         }
+        $pageId = $page->getId();
+
         try {
             $this->validateLayoutUpdate($page);
+            if ($pageId) {
+                $page = $this->hydrator->hydrate($this->getById($pageId), $this->hydrator->extract($page));
+            }
             $this->resource->save($page);
             $this->identityMap->add($page);
         } catch (\Exception $exception) {
@@ -248,6 +263,7 @@ private function getCollectionProcessor()
     {
         if (!$this->collectionProcessor) {
             $this->collectionProcessor = \Magento\Framework\App\ObjectManager::getInstance()->get(
+                // phpstan:ignore "Class Magento\Cms\Model\Api\SearchCriteria\PageCollectionProcessor not found."
                 \Magento\Cms\Model\Api\SearchCriteria\PageCollectionProcessor::class
             );
         }

app/code/Magento/Cms/etc/di.xml

@@ -193,6 +193,7 @@
     <type name="Magento\Cms\Model\PageRepository">
         <arguments>
             <argument name="collectionProcessor" xsi:type="object">Magento\Cms\Model\Api\SearchCriteria\PageCollectionProcessor</argument>
+            <argument name="hydrator" xsi:type="object">Magento\Framework\EntityManager\AbstractModelHydrator</argument>
         </arguments>
     </type>
     <virtualType name="Magento\Cms\Model\Api\SearchCriteria\CollectionProcessor\BlockFilterProcessor" type="Magento\Framework\Api\SearchCriteria\CollectionProcessor\FilterProcessor">