<?php
    /**
     * Upload the file of the field.
     *
     * @param string $value The value of the field
     *
     * @api
     */
    public function upload($value)
    {
        if (null !== $value && is_readable($value)) {
            $error = UPLOAD_ERR_OK;
            $size = filesize($value);
            $name = basename($value);

            // copy to a tmp location
            $tmp = tempnam(sys_get_temp_dir(), 'upload');
            unlink($tmp);
            copy($value, $tmp);
            $value = $tmp;
        } else {
            $error = UPLOAD_ERR_NO_FILE;
            $size = 0;
            $name = '';
            $value = '';
        }

        $this->value = array('name' => $name, 'type' => '', 'tmp_name' => $value, 'error' => $error, 'size' => $size);
    }

    /**
     * Sets the value of the field.
     *
     * @param string $value The value of the field
     */
    public function setValue($value, $raw = false)
    {
        if ($raw) {
            parent::setValue($value);
        } else {
            $this->upload($value);
        }
    }

<?php
    protected function addPostFiles($request, array $files, $arrayName = '')
    {
        if (!$request instanceof EntityEnclosingRequestInterface) {
            return;
        }

        foreach ($files as $name => $info) {
            if (!empty($arrayName)) {
                $name = $arrayName . '[' . $name . ']';
            }

            if (isset($info['tmp_name']) && '' !== $info['tmp_name']) {
                $request->addPostFile($name, $info['tmp_name']);
            } elseif (is_array($info)) {
                $this->addPostFiles($request, $info, $name);
+          } else {
+              $request->addPostFile($name, $info);
+          }
        }
    }

<?php
    /**
     * Attaches file path to file field located by it's XPath query.
     *
     * @param string $xpath
     * @param string $path
     */
    public function attachFile($xpath, $path)
    {
        $this->getFormField($xpath)->setValue($path, true);
    }