Upcast attributes in any variable

Closes #3406011

src/Controller/ServerEndpointController.php

@@ -186,9 +186,12 @@ class ServerEndpointController extends ControllerBase {
   private function generateRenderArray(Component $component, array $context): array {
     $metadata = $component->metadata;
     // Try to convert a key-value attributes property into the Drupal object.
-    if ($this->attributesPropNeedsUpcasting($context, $metadata)) {
-      $context['attributes'] = new Attribute($context['attributes']);
-    };
+    foreach ($context as $key => $value) {
+      if ($this->attributesPropNeedsUpcasting($context, $key, $metadata)) {
+        $context[$key] = new Attribute($value);
+      }
+    }
+
     $block_names = array_keys($metadata->slots);
     $slots = array_map(
       static fn (string $slot_str) => [
@@ -218,13 +221,14 @@ class ServerEndpointController extends ControllerBase {
    *
    * @param array $context
    *   The template context.
+   * @param string $key
    * @param \Drupal\sdc\Component\ComponentMetadata $metadata
    *   The component metadata.
    */
-  private function attributesPropNeedsUpcasting(array $context, ComponentMetadata $metadata) {
+  private function attributesPropNeedsUpcasting(array $context, string $key, ComponentMetadata $metadata) {
     $properties = $metadata->schema['properties'] ?? [];
-    $context_has_attributes = is_array($context['attributes'] ?? NULL);
-    $metadata_has_attributes = ($properties['attributes']['type'][0] ?? NULL) === "Drupal\Core\Template\Attribute";
+    $context_has_attributes = is_array($context[$key] ?? NULL);
+    $metadata_has_attributes = ($properties[$key]['type'][0] ?? NULL) === "Drupal\Core\Template\Attribute";
     return $context_has_attributes && $metadata_has_attributes;
   }