added a way to lazy load mounted applications

doc/usage.rst

@@ -417,6 +417,11 @@ one::
 Now, blog posts are available under the ``/blog/post/{id}`` route, along side
 any other routes you might have defined.
 
+If you mount many applications, you might want to avoid the overhead of
+loading them all on each request by using the ``LazyApplication`` wrapper::
+
+    $blog = new LazyApplication(__DIR__.'/blog.php');
+
 Pitfalls
 --------
 

src/Silex/LazyApplication.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;
+
+use Symfony\Component\HttpFoundation\Request;
+
+/**
+ * A Lazy application wrapper.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class LazyApplication
+{
+    protected $app;
+
+    public function __construct($app)
+    {
+        $this->app = $app;
+    }
+
+    public function __invoke(Request $request, $prefix)
+    {
+        if (!$this->app instanceof Application) {
+            $this->app = require $this->app;
+        }
+
+        return $this->app->__invoke($request, $prefix);
+    }
+}

tests/Silex/Tests/FunctionalTest.php

@@ -12,6 +12,7 @@
 namespace Silex\Tests;
 
 use Silex\Application;
+use Silex\LazyApplication;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 
@@ -69,4 +70,28 @@ class FunctionalTest extends \PHPUnit_Framework_TestCase
         $response = $app->handle(Request::create('/hello/Silex'));
         $this->assertEquals('Silex', $response->getContent());
     }
+
+    public function testLazyMountWithAnExternalFile()
+    {
+        $tmp = sys_get_temp_dir().'/SilexLazyApp.php';
+        file_put_contents($tmp, <<<'EOF'
+<?php
+
+$app = new Silex\Application();
+$app->get('/{name}', function ($name) { return new Symfony\Component\HttpFoundation\Response($name); });
+
+return $app;
+EOF
+        );
+
+        $mounted = new LazyApplication($tmp);
+
+        $app = new Application();
+        $app->mount('/hello', $mounted);
+
+        $response = $app->handle(Request::create('/hello/Silex'));
+        $this->assertEquals('Silex', $response->getContent());
+
+        unlink($tmp);
+    }
 }