File upload fields in the D8 Webform module don't show my custom 'required' message when they fail validation.

Here's the YAML source of a simple Webform:

  '#type': managed_file
  '#title': CV
  '#required': true
  '#required_error': 'Please upload a copy of your CV.'
  '#file_extensions': 'doc docx pdf odt rtf'
  '#type': document_file
  '#title': 'Test document'
  '#required': true
  '#required_error': 'Custom missing document file message.'
  '#format_items': comma

Instead of Please upload a copy of your CV etc., I get the default:

CV field is required.
Test document field is required.

I've run drush webform:repair
I've tested this on an otherwise empty form.
I've also cleared Drupal's cache.

Site setup:

Drupal 8.5.4.
No custom code yet.
(edit: we've since established it's nothing to do with contrib modules)

  • I was able to reproduce it, so it's a bug. – No Sssweat Jun 19 '18 at 3:16
  • I suggest you report it over at the issues page. The module's creator & maintainer jrockowitz is pretty quick at fixing them. – No Sssweat Jun 19 '18 at 7:57
  • Drupal core does not currently support the #required_error property for managed file uploads. @see \Drupal\file\Element\ManagedFile::validateManagedFile. We might need to remove this feature. – jrockowitz Jun 19 '18 at 12:51
  • Added my own answer, tidied question. – William Turrell Jun 20 '18 at 10:43

The error message for managed_file fields is added by ManagedFile::validateManagedFile - it does not support #required_error - the 'file missing' message (and others) are hardcoded:

      ->setError($element, t('@name field is required.', [
      '@name' => $element['#title'],

This is presumably because of the multiple types of error possible:

  • file does not exist
  • file is "not referenced" (it exists but is "unmanaged" - i.e. orphaned as far as DB concerned - see function docs linked above)
  • or, in our case, a file has not been uploaded at all


I bypassed this by adding my own validation to the form.

The Webform module has hook_webform_submission_form_alter - you can use this to append your own validation method:

function mymodule_webform_submission_form_alter(&$form, FormStateInterface $form_state, $form_id) {
    if ( $form['#webform_id'] != 'application' ) {
        // only do this for the specified form

    $form['#validate'][] = 'mymodule_fix_webform_validation';

function mymodule_fix_webform_validation($form, &$form_state) {

    // grab all the existing errors
    $errors = $form_state->getErrors();

    if ( isset( $errors['cv'] ) &&
         $errors['cv']->getUntranslatedString() == '@name field is required.' ) {
         // if (a) there's an error for this field, and
         // (b) it's the correct TYPE of error

         // reconstruct the error message
         // (you might add translatable strings if you need them)
         $errors['cv']->__construct( 'Please upload a copy of your CV.' );


(Decided to use the constructor from reading this answer to a similar question.)

Things I tried first:

The standard approach is to use $form_state->setError() or setErrorByName() - but neither appeared to have any effect on the error array - don't understand why.

On the actual form, the field was nested in a Webform "section"…


…so assumed I should supply the full array to setError(), for it to pull out the value of #parents and use that to construct the key. Except the error is actually stored as a flat 'cv' key, without the parent. Trying to set the 'cv' error using ByName didn't work either.

Overriding strings:

An alternative would be override the string (at time of writing, needs to be done programmatically: the string overrides module is not yet ready for D8). Add the following to settings.php:

$settings['locale_custom_strings_en'][''] = array(
    '@name field is required.' => 'Hello world!',

But this is a very broad brush and will apply to every file input on every form (plus anywhere else the phrase "@name field is required." is used - you can't specify the @name placeholder).

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