refactor: replace class override with new hook to flush webp images

Refs: RW-816

html/modules/custom/reliefweb_utility/reliefweb_utility.module

@@ -91,21 +91,26 @@ function reliefweb_utility_file_presave(FileInterface $file) {
 }
 
 /**
- * Implements hook_entity_type_alter().
+ * Implements hook_image_style_flush().
  *
- * Replace the image style class so we can properly delete webp versions of the
- * derivative images because this is not done by image_optimize_webp, notably
- * because there is no hook provided for that by the image module.
- *
- * Normally this runs after the imageapi_optimize_entity_type_alter() due to
- * the alphabetical order.
+ * Delete the webp version of the derivative images.
  */
-function reliefweb_utility_entity_type_alter(array &$entity_types) {
-  /** @var \Drupal\Core\Entity\EntityTypeInterface[] $entity_types */
-  if (isset($entity_types['image_style'])) {
-    $image_style = $entity_types['image_style'];
-    if ($image_style->getClass() === 'Drupal\imageapi_optimize\Entity\ImageStyleWithPipeline') {
-      $image_style->setClass('Drupal\reliefweb_utility\Entity\ImageStyleWithPipeline');
+function reliefweb_utility_image_style_flush($style, ?string $path = NULL) {
+  // Also delete the webp version of the image if it exists.
+  // @see Drupal\image\Entity\ImageStyle::flush()
+  if (isset($path)) {
+    /** @var \Drupal\Core\File\FileSystemInterface $file_system */
+    $file_system = \Drupal::service('file_system');
+    $derivative_uri = $style->buildUri($path);
+    $derivative_uri_webp = $derivative_uri . '.webp';
+
+    if (file_exists($derivative_uri_webp)) {
+      try {
+        $file_system->delete($derivative_uri_webp);
+      }
+      catch (FileException $exception) {
+        // Ignore failed deletion.
+      }
     }
   }
 }