--- /dev/null
+<?php
+
+namespace Drupal\node\ParamConverter;
+
+use Drupal\user\PrivateTempStoreFactory;
+use Symfony\Component\Routing\Route;
+use Drupal\Core\ParamConverter\ParamConverterInterface;
+
+/**
+ * Provides upcasting for a node entity in preview.
+ */
+class NodePreviewConverter implements ParamConverterInterface {
+
+ /**
+ * Stores the tempstore factory.
+ *
+ * @var \Drupal\user\PrivateTempStoreFactory
+ */
+ protected $tempStoreFactory;
+
+ /**
+ * Constructs a new NodePreviewConverter.
+ *
+ * @param \Drupal\user\PrivateTempStoreFactory $temp_store_factory
+ * The factory for the temp store object.
+ */
+ public function __construct(PrivateTempStoreFactory $temp_store_factory) {
+ $this->tempStoreFactory = $temp_store_factory;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function convert($value, $definition, $name, array $defaults) {
+ $store = $this->tempStoreFactory->get('node_preview');
+ if ($form_state = $store->get($value)) {
+ return $form_state->getFormObject()->getEntity();
+ }
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function applies($definition, $name, Route $route) {
+ if (!empty($definition['type']) && $definition['type'] == 'node_preview') {
+ return TRUE;
+ }
+ return FALSE;
+ }
+
+}