Check that files meet a given criteria.
This hook lets modules perform additional validation on files. They're able to report a failure by returning one or more error messages.
Drupal\file\File $file: The file entity being validated.
An array of error messages. If there are no problems with the file return an empty array.
Note: this list is generated by pattern matching, so it may include some functions that are not actually implementations of this hook.
function hook_file_validate(Drupal\file\File $file) {
$errors = array();
if (empty($file->filename)) {
$errors[] = t("The file's name is empty. Please give a name to the file.");
}
if (strlen($file->filename) > 255) {
$errors[] = t("The file's name exceeds the 255 characters limit. Please rename the file and try again.");
}
return $errors;
}