Adding a new SelfCheckingAsseticResource for compat with 2.8-3.0+

In 2.8, the SelfCheckingResourceInterface becomes available and you must
implement it for 3.0. An if statement either uses the old AsseticResource
(which does not include this interface) or the new SelfCheckingAsseticResource
if the interface exists.

Config/SelfCheckingAsseticResource.php

@@ -0,0 +1,25 @@
+<?php
+
+/*
+ * This file is part of the Symfony framework.
+ *
+ * (c) Fabien Potencier <[email protected]>
+ *
+ * This source file is subject to the MIT license that is bundled
+ * with this source code in the file LICENSE.
+ */
+
+namespace Symfony\Bundle\AsseticBundle\Config;
+
+use Symfony\Component\Config\Resource\SelfCheckingResourceInterface;
+
+/**
+ * Implements SelfCheckingResourceInterface required in Symfony 3.0.
+ *
+ * @author Ryan Weaver <[email protected]>
+ *
+ * @internal
+ */
+class SelfCheckingAsseticResource extends AsseticResource implements SelfCheckingResourceInterface
+{
+}

Routing/AsseticLoader.php

@@ -14,6 +14,7 @@
 use Assetic\Asset\AssetInterface;
 use Assetic\Factory\LazyAssetManager;
 use Symfony\Bundle\AsseticBundle\Config\AsseticResource;
+use Symfony\Bundle\AsseticBundle\Config\SelfCheckingAsseticResource;
 use Symfony\Component\Config\Loader\Loader;
 use Symfony\Component\Routing\Route;
 use Symfony\Component\Routing\RouteCollection;
@@ -56,7 +57,12 @@ public function load($routingResource, $type = null)
                 $resources = array($resources);
             }
             foreach ($resources as $resource) {
-                $routes->addResource(new AsseticResource($resource));
+                if (interface_exists('Symfony\Component\Config\Resource\SelfCheckingResourceInterface')) {
+                    $routes->addResource(new SelfCheckingAsseticResource($resource));
+                } else {
+                    // for BC with symfony/config 2.7 and lower
+                    $routes->addResource(new AsseticResource($resource));
+                }
             }
         }