Issue #3425688: Change file_validate functions to constraints

Closes #3425688

src/Element/FileUploader.php

@@ -90,6 +90,14 @@ class FileUploader extends ManagedFile {
     ];
 
     // Prepare the attachment settings.
+    if (isset($element['#upload_validators']['file_validate_extensions'][0])) {
+      $extensions = $element['#upload_validators']['file_validate_extensions'][0] ?? '';
+      $filesize = $element['#upload_validators']['file_validate_size'][0] ?? 0;
+    }
+    else {
+      $extensions = $element['#upload_validators']['FileExtension']['extensions'] ?? '';
+      $filesize = $element['#upload_validators']['FileSizeLimit']['fileLimit'] ?? 0;
+    }
     $settings = [
       'provider' => $element['#upload_provider'],
       'name' => $element['#name'],
@@ -97,8 +105,8 @@ class FileUploader extends ManagedFile {
         'xhr' => $url->toString(),
         'validators' => [
           'limit' => $element['#cardinality'],
-          'extensions' => preg_filter('/^/', '.', explode(' ', $element['#upload_validators']['file_validate_extensions'][0] ?? NULL)),
-          'filesize' => $element['#upload_validators']['file_validate_size'][0] ?? 0,
+          'extensions' => preg_filter('/^/', '.', explode(' ', $extensions)),
+          'filesize' => $filesize,
         ],
       ],
       'values' => $values,