added support for Twig runtime loaders

src/Silex/Provider/Twig/RuntimeLoader.php

+<?php
+
+/*
+ * This file is part of the Silex framework.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Silex\Provider\Twig;
+
+use Pimple\Container;
+
+/**
+ * Loads Twig extension runtimes via Pimple.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class RuntimeLoader implements \Twig_RuntimeLoaderInterface
+{
+    private $container;
+    private $mapping;
+
+    public function __construct(Container $container, array $mapping)
+    {
+        $this->container = $container;
+        $this->mapping = $mapping;
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function load($class)
+    {
+        if (isset($this->mapping[$class])) {
+            return $this->container[$this->mapping[$class]];
+        }
+    }
+}

src/Silex/Provider/TwigServiceProvider.php

@@ -13,6 +13,7 @@ namespace Silex\Provider;
 
 use Pimple\Container;
 use Pimple\ServiceProviderInterface;
+use Silex\Provider\Twig\RuntimeLoader;
 use Symfony\Bridge\Twig\AppVariable;
 use Symfony\Bridge\Twig\Extension\AssetExtension;
 use Symfony\Bridge\Twig\Extension\DumpExtension;
@@ -24,6 +25,7 @@ use Symfony\Bridge\Twig\Extension\HttpFoundationExtension;
 use Symfony\Bridge\Twig\Extension\HttpKernelExtension;
 use Symfony\Bridge\Twig\Form\TwigRendererEngine;
 use Symfony\Bridge\Twig\Form\TwigRenderer;
+use Symfony\Bridge\Twig\Extension\HttpKernelRuntime;
 
 /**
  * Twig integration for Silex.
@@ -118,6 +120,10 @@ class TwigServiceProvider implements ServiceProviderInterface
                 if (isset($app['var_dumper.cloner'])) {
                     $twig->addExtension(new DumpExtension($app['var_dumper.cloner']));
                 }
+
+                if (class_exists(HttpKernelRuntime::class)) {
+                    $twig->addRuntimeLoader($app['twig.runtime_loader']);
+                }
             }
 
             return $twig;
@@ -141,5 +147,20 @@ class TwigServiceProvider implements ServiceProviderInterface
         $app['twig.environment_factory'] = $app->protect(function ($app) {
             return new \Twig_Environment($app['twig.loader'], $app['twig.options']);
         });
+
+        $app['twig.runtime.httpkernel'] = function ($app) {
+            return new HttpKernelRuntime($app['fragment.handler']);
+        };
+
+        $app['twig.runtimes'] = function ($app) {
+            return array(
+                HttpKernelRuntime::class => 'twig.runtime.httpkernel',
+                TwigRenderer::class => 'twig.form.renderer',
+            );
+        };
+
+        $app['twig.runtime_loader'] = function ($app) {
+            return new RuntimeLoader($app, $app['twig.runtimes']);
+        };
     }
 }