#3508694 Adding JSC access control + trying to provide better error in denied deletion

Closes #3508694

src/Access/XbEntityCreateAccessCheck.php

+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\experience_builder\Access;
+
+use Drupal\Core\Access\AccessResult;
+use Drupal\Core\Access\AccessResultInterface;
+use Drupal\Core\Entity\EntityCreateAccessCheck;
+use Drupal\Core\Routing\Access\AccessInterface;
+use Drupal\Core\Routing\RouteMatchInterface;
+use Drupal\Core\Session\AccountInterface;
+use Symfony\Component\Routing\Route;
+
+/**
+ * Defines an access checker for entity creation allowing dynamic entity types.
+ *
+ * @todo Remove when https://www.drupal.org/project/drupal/issues/3516775 lands in Drupal core and XB requires a version that includes it.
+ */
+final class XbEntityCreateAccessCheck extends EntityCreateAccessCheck implements AccessInterface {
+
+  protected $requirementsKey = '_xb_entity_create_access';
+
+  /**
+   * {@inheritdoc}
+   */
+  public function access(Route $route, RouteMatchInterface $route_match, AccountInterface $account): AccessResultInterface {
+    [$entity_type, $bundle] = explode(':', $route->getRequirement($this->requirementsKey) . ':');
+
+    // Allow dynamic entity types.
+    $parameters = $route_match->getParameters();
+    if ($parameters->has($entity_type)) {
+      $entity_type = $parameters->get($entity_type);
+    }
+
+    // The bundle argument can contain request argument placeholders like
+    // {name}, loop over the raw variables and attempt to replace them in the
+    // bundle name. If a placeholder does not exist, it won't get replaced.
+    if ($bundle && str_contains($bundle, '{')) {
+      foreach ($route_match->getRawParameters()->all() as $name => $value) {
+        $bundle = str_replace('{' . $name . '}', $value, $bundle);
+      }
+      // If we were unable to replace all placeholders, deny access.
+      if (str_contains($bundle, '{')) {
+        return AccessResult::neutral(sprintf("Could not find '%s' request argument, therefore cannot check create access.", $bundle));
+      }
+    }
+    return $this->entityTypeManager->getAccessControlHandler($entity_type)->createAccess($bundle, $account, [], TRUE);
+  }
+
+}