Issue #3054902 by ricovandevin, dww, woprrr: Use deep merge when creating routes from parent routes

src/Routing/EventSubscriber/FormModesSubscriber.php

@@ -2,6 +2,7 @@
 
 namespace Drupal\form_mode_manager\Routing\EventSubscriber;
 
+use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Entity\EntityDisplayRepositoryInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
 use Drupal\Core\Routing\RouteSubscriberBase;
@@ -213,9 +214,9 @@ class FormModesSubscriber extends RouteSubscriberBase {
       $parent_route->getPath(),
       $this->formModeManager->getFormModeMachineName($form_mode_infos['id']),
     ]);
-    $route_defaults = array_merge($parent_route->getDefaults(), $this->getFormModeRouteDefaults($parent_route, $form_mode_infos));
-    $route_options = array_merge($parent_route->getOptions(), $this->getFormModeRouteOptions($form_mode_infos));
-    $route_requirements = array_merge($parent_route->getRequirements(), $this->getFormModeRouteRequirements($form_mode_infos));
+    $route_defaults = NestedArray::mergeDeep($parent_route->getDefaults(), $this->getFormModeRouteDefaults($parent_route, $form_mode_infos));
+    $route_options = NestedArray::mergeDeep($parent_route->getOptions(), $this->getFormModeRouteOptions($form_mode_infos));
+    $route_requirements = NestedArray::mergeDeep($parent_route->getRequirements(), $this->getFormModeRouteRequirements($form_mode_infos));
 
     return new Route($route_path, $route_defaults, $route_requirements, $route_options);
   }