Fatal error: Type of ResponsiveGalleryFormatter::$fileUrlGenerator must be FileUrlGeneratorInterface in Drupal 11.4+

Problem/Motivation

On Drupal 11.4.0 and newer, loading a page or rendering a field using the responsive_gallery formatter triggers a fatal error:

Fatal error: Type of Drupal\responsive_gallery\Plugin\Field\FieldFormatter\ResponsiveGalleryFormatter::$fileUrlGenerator must be Drupal\Core\File\FileUrlGeneratorInterface (as in class Drupal\image\Plugin\Field\FieldFormatter\ImageFormatter) in /path/to/modules/contrib/responsive_gallery/src/Plugin/Field/FieldFormatter/ResponsiveGalleryFormatter.php on line 29

Cause

In Drupal core 11.4.x, the parent class Drupal\image\Plugin\Field\FieldFormatter\ImageFormatter adopted PHP 8 constructor property promotion with explicit type declarations:

protected FileUrlGeneratorInterface $fileUrlGenerator

ResponsiveGalleryFormatter redeclares protected $fileUrlGenerator; without a type declaration, causing a fatal type mismatch in PHP 7.4+. 2. In addition, Drupal 11.4 introduced ?ImageDerivativeUtilities $imageDerivativeUtilities as the 11th parameter in ImageFormatter::__construct(). The constructor override in ResponsiveGalleryFormatter previously forwarded $route_match as the 11th argument into parent::__construct(), which leads to a TypeError.

Proposed resolution

1. Remove the redundant, untyped protected $fileUrlGenerator; property declaration (it is already declared and assigned with the proper type in the parent ImageFormatter).
2. Remove the custom constructor override.
3. Update ResponsiveGalleryFormatter::create() to call parent::create() and assign module-specific services (renderer and current_route_match) directly onto the instance:

public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
  $instance = parent::create($container, $configuration, $plugin_id, $plugin_definition);
  $instance->renderer = $container->get('renderer');
  $instance->routeMatch = $container->get('current_route_match');
  return $instance;
}

This prevents brittleness against future upstream changes to ImageFormatter's constructor parameters.

Remaining tasks

Review and test the attached patch.

Credits

Gemini