[Asset] Add support for preloading with links and HTTP/2 push

src/Symfony/Bridge/Twig/Extension/AssetExtension.php

@@ -12,6 +12,7 @@
 namespace Symfony\Bridge\Twig\Extension;
 
 use Symfony\Component\Asset\Packages;
+use Symfony\Component\Asset\Preload\PreloadManagerInterface;
 
 /**
  * Twig extension for the Symfony Asset component.
@@ -21,10 +22,12 @@ use Symfony\Component\Asset\Packages;
 class AssetExtension extends \Twig_Extension
 {
     private $packages;
+    private $preloadManager;
 
-    public function __construct(Packages $packages)
+    public function __construct(Packages $packages, PreloadManagerInterface $preloadManager = null)
     {
         $this->packages = $packages;
+        $this->preloadManager = $preloadManager;
     }
 
     /**
@@ -35,6 +38,7 @@ class AssetExtension extends \Twig_Extension
         return array(
             new \Twig_SimpleFunction('asset', array($this, 'getAssetUrl')),
             new \Twig_SimpleFunction('asset_version', array($this, 'getAssetVersion')),
+            new \Twig_SimpleFunction('preload', array($this, 'preload')),
         );
     }
 
@@ -67,6 +71,26 @@ class AssetExtension extends \Twig_Extension
         return $this->packages->getVersion($path, $packageName);
     }
 
+    /**
+     * Preloads an asset.
+     *
+     * @param string $path   A public path
+     * @param string $as     A valid destination according to https://fetch.spec.whatwg.org/#concept-request-destination
+     * @param bool   $nopush If this asset should not be pushed over HTTP/2
+     *
+     * @return string The path of the asset
+     */
+    public function preload($path, $as = '', $nopush = false)
+    {
+        if (null === $this->preloadManager) {
+            throw new \RuntimeException('A preload manager must be configured to use the "preload" function.');
+        }
+
+        $this->preloadManager->addResource($path, $as, $nopush);
+
+        return $path;
+    }
+
     /**
      * Returns the name of the extension.
      *

src/Symfony/Bridge/Twig/Tests/Extension/AssetExtensionTest.php

@@ -0,0 +1,44 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (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 Symfony\Bridge\Twig\Tests\Extension;
+
+use Symfony\Bridge\Twig\Extension\AssetExtension;
+use Symfony\Component\Asset\Packages;
+use Symfony\Component\Asset\Preload\PreloadManager;
+
+/**
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class AssetExtensionTest extends \PHPUnit_Framework_TestCase
+{
+    public function testGetAndPreloadAssetUrl()
+    {
+        if (!class_exists(PreloadManager::class)) {
+            $this->markTestSkipped('Requires Asset 3.3+.');
+        }
+
+        $preloadManager = new PreloadManager();
+        $extension = new AssetExtension(new Packages(), $preloadManager);
+
+        $this->assertEquals('/foo.css', $extension->preload('/foo.css', 'style', true));
+        $this->assertEquals('</foo.css>; rel=preload; as=style; nopush', $preloadManager->buildLinkValue());
+    }
+
+    /**
+     * @expectedException \RuntimeException
+     */
+    public function testNoConfiguredPreloadManager()
+    {
+        $extension = new AssetExtension(new Packages());
+        $extension->preload('/foo.css');
+    }
+}

src/Symfony/Bundle/FrameworkBundle/Resources/config/assets.xml

@@ -38,5 +38,13 @@
 
         <service id="assets.empty_version_strategy" class="Symfony\Component\Asset\VersionStrategy\EmptyVersionStrategy" public="false" />
 
+        <service id="assets.preload_manager" class="Symfony\Component\Asset\Preload\PreloadManager" public="false" />
+
+        <service id="asset.preload_listener" class="Symfony\Component\Asset\EventListener\PreloadListener">
+            <argument type="service" id="assets.preload_manager" />
+
+            <tag name="kernel.event_subscriber" />
+        </service>
+
     </services>
 </container>

src/Symfony/Bundle/FrameworkBundle/Tests/DependencyInjection/FrameworkExtensionTest.php

@@ -375,6 +375,12 @@ abstract class FrameworkExtensionTest extends TestCase
         $this->assertEquals('assets.custom_version_strategy', (string) $defaultPackage->getArgument(1));
     }
 
+    public function testAssetHasPreloadListener()
+    {
+        $container = $this->createContainerFromFile('assets');
+        $this->assertTrue($container->hasDefinition('asset.preload_listener'));
+    }
+
     public function testTranslator()
     {
         $container = $this->createContainerFromFile('full');

src/Symfony/Bundle/FrameworkBundle/composer.json

@@ -60,6 +60,7 @@
     "conflict": {
         "phpdocumentor/reflection-docblock": "<3.0",
         "phpdocumentor/type-resolver": "<0.2.0",
+        "symfony/asset": "<3.3",
         "symfony/console": "<3.3"
     },
     "suggest": {

src/Symfony/Bundle/TwigBundle/Resources/config/twig.xml

@@ -70,6 +70,7 @@
 
         <service id="twig.extension.assets" class="Symfony\Bridge\Twig\Extension\AssetExtension" public="false">
             <argument type="service" id="assets.packages" />
+            <argument type="service" id="assets.preload_manager" on-invalid="ignore" />
         </service>
 
         <service id="twig.extension.code" class="Symfony\Bridge\Twig\Extension\CodeExtension" public="false">

src/Symfony/Component/Asset/EventListener/PreloadListener.php

@@ -0,0 +1,55 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (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 Symfony\Component\Asset\EventListener;
+
+use Symfony\Component\Asset\Preload\PreloadManager;
+use Symfony\Component\Asset\Preload\PreloadManagerInterface;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
+use Symfony\Component\HttpKernel\KernelEvents;
+
+/**
+ * Adds the preload Link HTTP header to the response.
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class PreloadListener implements EventSubscriberInterface
+{
+    private $preloadManager;
+
+    public function __construct(PreloadManagerInterface $preloadManager)
+    {
+        $this->preloadManager = $preloadManager;
+    }
+
+    public function onKernelResponse(FilterResponseEvent $event)
+    {
+        if (!$event->isMasterRequest()) {
+            return;
+        }
+
+        if ($value = $this->preloadManager->buildLinkValue()) {
+            $event->getResponse()->headers->set('Link', $value, false);
+
+            // Free memory
+            $this->preloadManager->clear();
+        }
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public static function getSubscribedEvents()
+    {
+        return array(KernelEvents::RESPONSE => 'onKernelResponse');
+    }
+}

src/Symfony/Component/Asset/Preload/PreloadManager.php

@@ -0,0 +1,58 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (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 Symfony\Component\Asset\Preload;
+
+/**
+ * Manages preload HTTP headers.
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class PreloadManager implements PreloadManagerInterface
+{
+    private $resources = array();
+
+    /**
+     * {@inheritdoc}
+     */
+    public function addResource($uri, $as = '', $nopush = false)
+    {
+        $this->resources[$uri] = array('as' => $as, 'nopush' => $nopush);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function clear()
+    {
+        $this->resources = array();
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function buildLinkValue()
+    {
+        if (!$this->resources) {
+            return;
+        }
+
+        $parts = array();
+        foreach ($this->resources as $uri => $options) {
+            $as = '' === $options['as'] ? '' : sprintf('; as=%s', $options['as']);
+            $nopush = $options['nopush'] ? '; nopush' : '';
+
+            $parts[] = sprintf('<%s>; rel=preload%s%s', $uri, $as, $nopush);
+        }
+
+        return implode(',', $parts);
+    }
+}

src/Symfony/Component/Asset/Preload/PreloadManagerInterface.php

@@ -0,0 +1,43 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (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 Symfony\Component\Asset\Preload;
+
+/**
+ * Manages resources to preload according to the W3C "Preload" specification.
+ *
+ * @see https://www.w3.org/TR/preload/
+ *
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+interface PreloadManagerInterface
+{
+    /**
+     * Adds an element to the list of resources to preload.
+     *
+     * @param string $uri    The resource URI
+     * @param string $as     A valid destination according to https://fetch.spec.whatwg.org/#concept-request-destination
+     * @param bool   $nopush If this asset should not be pushed over HTTP/2
+     */
+    public function addResource($uri, $as = '', $nopush = false);
+
+    /**
+     * Clears the list of resources.
+     */
+    public function clear();
+
+    /**
+     * Builds the value of the preload Link HTTP header.
+     *
+     * @return string|null
+     */
+    public function buildLinkValue();
+}

src/Symfony/Component/Asset/Tests/EventListener/PreloadListenerTest.php

@@ -0,0 +1,55 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (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 Symfony\Component\Asset\Tests\EventListener;
+
+use Symfony\Component\Asset\EventListener\PreloadListener;
+use Symfony\Component\Asset\Preload\PreloadManager;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
+use Symfony\Component\HttpKernel\KernelEvents;
+
+/**
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class PreloadListenerTest extends \PHPUnit_Framework_TestCase
+{
+    public function testOnKernelResponse()
+    {
+        $manager = new PreloadManager();
+        $manager->addResource('/foo');
+
+        $subscriber = new PreloadListener($manager);
+        $response = new Response('', 200, array('Link' => '<https://demo.api-platform.com/docs.jsonld>; rel="http://www.w3.org/ns/hydra/core#apiDocumentation"'));
+
+        $event = $this->getMockBuilder(FilterResponseEvent::class)->disableOriginalConstructor()->getMock();
+        $event->method('isMasterRequest')->willReturn(true);
+        $event->method('getResponse')->willReturn($response);
+
+        $subscriber->onKernelResponse($event);
+
+        $this->assertInstanceOf(EventSubscriberInterface::class, $subscriber);
+
+        $expected = array(
+            '<https://demo.api-platform.com/docs.jsonld>; rel="http://www.w3.org/ns/hydra/core#apiDocumentation"',
+            '</foo>; rel=preload',
+        );
+
+        $this->assertEquals($expected, $response->headers->get('Link', null, false));
+        $this->assertNull($manager->buildLinkValue());
+    }
+
+    public function testSubscribedEvents()
+    {
+        $this->assertEquals(array(KernelEvents::RESPONSE => 'onKernelResponse'), PreloadListener::getSubscribedEvents());
+    }
+}

src/Symfony/Component/Asset/Tests/Preload/PreloadManagerTest.php

@@ -0,0 +1,30 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (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 Symfony\Component\Asset\Preload;
+
+/**
+ * @author Kévin Dunglas <dunglas@gmail.com>
+ */
+class PreloadManagerTest extends \PHPUnit_Framework_TestCase
+{
+    public function testManageResources()
+    {
+        $manager = new PreloadManager();
+        $this->assertInstanceOf(PreloadManagerInterface::class, $manager);
+
+        $manager->addResource('/foo/bar.js', 'script', false);
+        $manager->addResource('/foo/baz.css');
+        $manager->addResource('/foo/bat.png', 'image', true);
+
+        $this->assertEquals('</foo/bar.js>; rel=preload; as=script,</foo/baz.css>; rel=preload,</foo/bat.png>; rel=preload; as=image; nopush', $manager->buildLinkValue());
+    }
+}

src/Symfony/Component/Asset/composer.json

@@ -22,7 +22,8 @@
         "symfony/http-foundation": ""
     },
     "require-dev": {
-        "symfony/http-foundation": "~2.8|~3.0"
+        "symfony/http-foundation": "~2.8|~3.0",
+        "symfony/http-kernel": "~2.8|~3.0"
     },
     "autoload": {
         "psr-4": { "Symfony\\Component\\Asset\\": "" },