No response when ValidationException is thrown using Plupload and Symfony3

Sorry previous version was incorrect.

OneupUploaderBundle catches exceptions in a controller and pass them to error_handler service.

class PluploadController extends AbstractChunkedController{    public function upload()    {        ...        foreach ($files as $file) {            try {                $chunked ?                    $this->handleChunkedUpload($file, $response, $request) :                    $this->handleUpload($file, $response, $request)                ;            } catch (UploadException $e) {                $this->errorHandler->addException($response, $e);            }        }        return $this->createSupportedJsonResponse($response->assemble());    }

You should check which error handler is used for your application. Looks like by default for Plupload the bundle set up NoopErrorHandler which does nothing with your exception.

Oneup\UploaderBundle\Uploader\ErrorHandler\NoopErrorHandler

public function addException(AbstractResponse $response, Exception $exception){    // noop}

errorhandler.xml

 <service id="oneup_uploader.error_handler.plupload" class="%oneup_uploader.error_handler.noop.class%" public="false" />

To get Response of desired shape you should set up BlueimpErrorHandler or to define a custom handler.

Oneup\UploaderBundle\Uploader\ErrorHandler\BlueimpErrorHandler

public function addException(AbstractResponse $response, Exception $exception){    $message = $this->translator->trans($exception->getMessage(), array(), 'OneupUploaderBundle');    $response->addToOffset(array('error' => $message), array('files'));}

OT: Using exceptions in the validator that way will bring bad experience to a user. The user should see all errors with an uploaded file not just first one. You should collect all errors and then throw an exception. For example:

    ...    if (in_array($full_file_name, $this->banned_files))    {        throw new ValidationException('error.file_exists');    }    $errors = [];    // Is file mime type the same as extension mime type    $mime_type_position = array_search($file_extension, $this->file_extension_array);    if ($mime_type_position !== false)    {        $mime_type_by_extension = $this->file_type_array[$mime_type_position];        if ($mime_type_by_extension !== $file_mime_type)        {            $errors[] = 'error.mime_type_mismatch';        }    }    // Is file type not in activated file type array    if (!in_array($file_mime_type, $this->file_type_array))    {        $errors[] = 'error.forbidden_mime_type';    }    if (empty($errors)) {        throw new ValidationException(implode(', ', $errors));    }    ...