Drupal 8 Webform add prefix to uploaded file names - drupal-8

Question

I have a webform with a file upload field. I need do one of two things. Either upload files into a subfolder inside the private area, OR, add a prefix to the filename that the user is uploading. The user can upload several files. The webform editor allows you to 'Rename' the file and use tokens for this, but I don't see any way of preserving the original file name. I can hack getFileDestinationUri() in WebformManagedFileBase.php to do what I want, but obviously I would rather not do that. Am I missing something?

Answer 1

It turns out that you can use the drupal form alter hook to alter the destination. I had thought of this but felt if was unlikely to work. It does.
Below is MY code solution: (I may be missing container types)
function _mymodule_fix_elements(&$elements) {
foreach ($elements as $key => &$element) {
if (strpos($key, '#') !== 0) {
if (is_array($element)) {
if (isset($element['#type'])) {
if (($element['#type'] == 'fieldset') ||
($element['#type'] == 'webform_flexbox') ||
($element['#type'] == 'container')) {
_mymodule_fix_elements($element);
} else if ($element['#type'] == 'managed_file') {
$pattern = $element['#upload_location'];
if (strpos($pattern, 'private:') === 0) {
$element['#upload_location'] = $pattern . '/' . $key;
}
}
}
}
}
}
}
function mymodule_form_alter(&$form, &$form_state, $id) {
if (strpos($id, 'webform_') === 0) {
_mymodule_fix_elements($form['elements']);
}
}