The Drupal\webform_dropzonejs\Element\WebformDropzonejs::preRenderDropzoneJs uses $element['#extensions'] = $element['#upload_validators']['file_validate_extensions'][0] ?? ''; to determine valid file extensions. This doesn't seem to be valid anymore in newer versions of webform/Drupal.
https://www.drupal.org/project/webform/issues/3465838 ✨ Drupal 11 compatibility fixes for webform Active handles this as follows:
- $validators = ['file_validate_extensions' => ['csv']];
+ $validators = ['FileExtension' => ['extensions' => 'csv']];
We need to do the same.
Update to a recent version of core/webform and try to drag and drop to upload a file. Upload fails no matter what the file type is. Futher, clicking "select files" doesn't even allow selection of any files because it thinks there are no valid extensions.
Update extension validation.
update extensions validation
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