Why are $ _Files and/or HTTPFoundation\FileBag invalid in custom module Controller?

I have noticed a very strange issue with accessing an individual file from the $ _FILES object or the Symfony derived \Symfony\Component\HTTPFoundation\FileBag from within a custom module controller.

The exact location of the issue seems to be in Symfony\Component\HttpKernel\HttpKernel -> handleRaw

Specifically, the file exists prior dispatching the KernelEvent::REQUEST but it does not after.

// request $  event = new GetResponseEvent($  this, $  request, $  type);  // THE FILE EXISTS HERE // file_exists( $  request->files->get(0)->getRealPath()) == TRUE  $  this->dispatcher->dispatch(KernelEvents::REQUEST, $  event);  // THE FILE DOES NOT EXISTS HERE // file_exists( $  request->files->get(0)->getRealPath()) == FALSE 

Here is the entire method for reference also including some code to move the file, which works as expected as long as it is before the event dispatch.

  /**  * Handles a request to convert it to a response.  *  * Exceptions are not caught.  *  * @param Request $  request A Request instance  * @param int     $  type    The type of the request (one of HttpKernelInterface::MASTER_REQUEST or HttpKernelInterface::SUB_REQUEST)  *  * @return Response A Response instance  *  * @throws \LogicException       If one of the listener does not behave as expected  * @throws NotFoundHttpException When controller cannot be found  */ private function handleRaw(Request $  request, $  type = self::MASTER_REQUEST) {     $  this->requestStack->push($  request);       $  directory = \Drupal::service('file_system')->realpath(file_default_scheme() . "://");      /* @var \Symfony\Component\HttpFoundation\File\UploadedFile $  uploadedFile*/     $  uploadedFile = $  request->files->get(0);      if (is_uploaded_file($  uploadedFile->getRealPath())){       $  success = $  uploadedFile->move($  directory);     }      // request     $  event = new GetResponseEvent($  this, $  request, $  type);     $  this->dispatcher->dispatch(KernelEvents::REQUEST, $  event);      if ($  event->hasResponse()) {         return $  this->filterResponse($  event->getResponse(), $  request, $  type);     }      // load controller     if (false === $  controller = $  this->resolver->getController($  request)) {         throw new NotFoundHttpException(sprintf('Unable to find the controller for path "%s". The route is wrongly configured.', $  request->getPathInfo()));     }      $  event = new FilterControllerEvent($  this, $  controller, $  request, $  type);     $  this->dispatcher->dispatch(KernelEvents::CONTROLLER, $  event);     $  controller = $  event->getController();      // controller arguments     $  arguments = $  this->argumentResolver->getArguments($  request, $  controller);      $  event = new FilterControllerArgumentsEvent($  this, $  controller, $  arguments, $  request, $  type);     $  this->dispatcher->dispatch(KernelEvents::CONTROLLER_ARGUMENTS, $  event);     $  controller = $  event->getController();     $  arguments = $  event->getArguments();      // call controller     $  response = call_user_func_array($  controller, $  arguments);      // view     if (!$  response instanceof Response) {         $  event = new GetResponseForControllerResultEvent($  this, $  request, $  type, $  response);         $  this->dispatcher->dispatch(KernelEvents::VIEW, $  event);          if ($  event->hasResponse()) {             $  response = $  event->getResponse();         }          if (!$  response instanceof Response) {             $  msg = sprintf('The controller must return a response (%s given).', $  this->varToString($  response));              // the user may have forgotten to return something             if (null === $  response) {                 $  msg .= ' Did you forget to add a return statement somewhere in your controller?';             }             throw new \LogicException($  msg);         }     }      return $  this->filterResponse($  response, $  request, $  type); } 

I am trying to write a custom GraphQL module mutation plugin that handles file uploads and unless I can get access to the file object from the POST request, I don’t think this will be possible.

Any thoughts are greatly appreciated.