.../Plugin/rest/resource/FileUploadResource.php    | 82 +++++++++++++++++++---
 1 file changed, 73 insertions(+), 9 deletions(-)

diff --git a/core/modules/file/src/Plugin/rest/resource/FileUploadResource.php b/core/modules/file/src/Plugin/rest/resource/FileUploadResource.php
index 82e42c1fa5..dc4e592720 100644
--- a/core/modules/file/src/Plugin/rest/resource/FileUploadResource.php
+++ b/core/modules/file/src/Plugin/rest/resource/FileUploadResource.php
@@ -2,9 +2,13 @@
 
 namespace Drupal\file\Plugin\rest\resource;
 
+use Drupal\Core\Config\Config;
 use Drupal\Core\Entity\EntityConstraintViolationListInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
+use Drupal\Core\File\FileSystemInterface;
+use Drupal\Core\Lock\LockBackendInterface;
 use Drupal\Core\Session\AccountInterface;
+use Drupal\Core\Utility\Token;
 use Drupal\file\FileFieldUploader;
 use Drupal\rest\ModifiedResourceResponse;
 use Drupal\rest\Plugin\ResourceBase;
@@ -14,6 +18,7 @@
 use Drupal\rest\RequestHandler;
 use Psr\Log\LoggerInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesserInterface;
 use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 use Symfony\Component\HttpKernel\Exception\UnprocessableEntityHttpException;
@@ -62,11 +67,11 @@ class FileUploadResource extends ResourceBase {
   const BYTES_TO_READ = 8192;
 
   /**
-   * The file field uploader.
+   * The file system service.
    *
-   * @var \Drupal\file\FileFieldUploader
+   * @var \Drupal\Core\File\FileSystemInterface
    */
-  protected $fileFieldUploader;
+  protected $fileSystem;
 
   /**
    * The entity type manager.
@@ -89,6 +94,39 @@ class FileUploadResource extends ResourceBase {
    */
   protected $currentUser;
 
+  /**
+   * The MIME type guesser.
+   *
+   * @var \Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesserInterface
+   */
+  protected $mimeTypeGuesser;
+
+  /**
+   * The token replacement instance.
+   *
+   * @var \Drupal\Core\Utility\Token
+   */
+  protected $token;
+
+  /**
+   * The lock service.
+   *
+   * @var \Drupal\Core\Lock\LockBackendInterface
+   */
+  protected $lock;
+
+  /**
+   * @var \Drupal\Core\Config\ImmutableConfig
+   */
+  protected $systemFileConfig;
+
+  /**
+   * The file field uploader.
+   *
+   * @var \Drupal\file\FileFieldUploader
+   */
+  protected $fileFieldUploader;
+
   /**
    * Constructs a FileUploadResource instance.
    *
@@ -102,21 +140,42 @@ class FileUploadResource extends ResourceBase {
    *   The available serialization formats.
    * @param \Psr\Log\LoggerInterface $logger
    *   A logger instance.
-   * @param \Drupal\file\FileFieldUploader $file_field_uploader
-   *   The file field uploader service.
+   * @param \Drupal\Core\File\FileSystemInterface $file_system
+   *   The file system service.
    * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
    *   The entity type manager.
    * @param \Drupal\Core\Entity\EntityFieldManagerInterface $entity_field_manager
    *   The entity field manager.
    * @param \Drupal\Core\Session\AccountInterface $current_user
    *   The currently authenticated user.
+   * @param \Symfony\Component\HttpFoundation\File\MimeType\MimeTypeGuesserInterface $mime_type_guesser
+   *   The MIME type guesser.
+   * @param \Drupal\Core\Utility\Token $token
+   *   The token replacement instance.
+   * @param \Drupal\Core\Lock\LockBackendInterface $lock
+   *   The lock service.
+   * @param \Drupal\Core\Config\Config $system_file_config
+   *   The system file configuration.
+   * @param \Drupal\file\FileFieldUploader $file_field_uploader
+   *   The file field uploader.
    */
-  public function __construct(array $configuration, $plugin_id, $plugin_definition, $serializer_formats, LoggerInterface $logger, FileFieldUploader $file_field_uploader, EntityTypeManagerInterface $entity_type_manager, EntityFieldManagerInterface $entity_field_manager, AccountInterface $current_user) {
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, $serializer_formats, LoggerInterface $logger, FileSystemInterface $file_system, EntityTypeManagerInterface $entity_type_manager, EntityFieldManagerInterface $entity_field_manager, AccountInterface $current_user, MimeTypeGuesserInterface $mime_type_guesser, Token $token, LockBackendInterface $lock, Config $system_file_config, FileFieldUploader $file_field_uploader = NULL) {
     parent::__construct($configuration, $plugin_id, $plugin_definition, $serializer_formats, $logger);
-    $this->fileFieldUploader = $file_field_uploader;
+    $this->fileSystem = $file_system;
     $this->entityTypeManager = $entity_type_manager;
     $this->entityFieldManager = $entity_field_manager;
     $this->currentUser = $current_user;
+    $this->mimeTypeGuesser = $mime_type_guesser;
+    $this->token = $token;
+    $this->lock = $lock;
+    $this->systemFileConfig = $system_file_config;
+    if ($file_field_uploader instanceof FileFieldUploader) {
+      $this->fileFieldUploader = $file_field_uploader;
+    }
+    else {
+      @trigger_error("The 'file.uploader.field' service must be passed to FileUploadResource::__construct(), it is required before Drupal 9.0.0. See https://www.drupal.org/project/drupal/issues/2940383.", E_USER_DEPRECATED);
+      $this->fileFieldUploader = \Drupal::service('file.uploader.field');
+    }
   }
 
   /**
@@ -129,10 +188,15 @@ public static function create(ContainerInterface $container, array $configuratio
       $plugin_definition,
       $container->getParameter('serializer.formats'),
       $container->get('logger.factory')->get('rest'),
-      $container->get('file.uploader.field'),
+      $container->get('file_system'),
       $container->get('entity_type.manager'),
       $container->get('entity_field.manager'),
-      $container->get('current_user')
+      $container->get('current_user'),
+      $container->get('file.mime_type.guesser'),
+      $container->get('token'),
+      $container->get('lock'),
+      $container->get('config.factory')->get('system.file'),
+      $container->get('file.uploader.field')
     );
   }