[AssetMapper] Automatically preload CSS files

weaverryan · weaverryan · commit edcc1e9ee6ae · 2023-10-03T13:25:32.000-04:00
diff --git a/src/Symfony/Bundle/FrameworkBundle/Resources/config/asset_mapper.php b/src/Symfony/Bundle/FrameworkBundle/Resources/config/asset_mapper.php
@@ -191,6 +191,7 @@
                 param('kernel.charset'),
                 abstract_arg('polyfill URL'),
                 abstract_arg('script HTML attributes'),
+                service('request_stack'),
             ])
 
         ->set('asset_mapper.importmap.command.require', ImportMapRequireCommand::class)
diff --git a/src/Symfony/Component/AssetMapper/CHANGELOG.md b/src/Symfony/Component/AssetMapper/CHANGELOG.md
@@ -8,6 +8,7 @@ CHANGELOG
  * Add CSS support to the importmap
  * Add "entrypoints" concept to the importmap
  * Allow relative path strings in the importmap
+ * Automatically set `_links` attribute for preload CSS files for WebLink integration
  * Add `PreAssetsCompileEvent` event when running `asset-map:compile`
  * Add support for importmap paths to use the Asset component (for subdirectories)
  * Removed the `importmap:export` command
diff --git a/src/Symfony/Component/AssetMapper/ImportMap/ImportMapRenderer.php b/src/Symfony/Component/AssetMapper/ImportMap/ImportMapRenderer.php
@@ -11,7 +11,13 @@
 
 namespace Symfony\Component\AssetMapper\ImportMap;
 
+use Psr\Link\EvolvableLinkProviderInterface;
 use Symfony\Component\Asset\Packages;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\WebLink\EventListener\AddLinkHeaderListener;
+use Symfony\Component\WebLink\GenericLinkProvider;
+use Symfony\Component\WebLink\Link;
 
 /**
  * @author Kévin Dunglas <kevin@dunglas.dev>
@@ -27,6 +33,7 @@ public function __construct(
         private readonly string $charset = 'UTF-8',
         private readonly string|false $polyfillUrl = ImportMapManager::POLYFILL_URL,
         private readonly array $scriptAttributes = [],
+        private readonly ?RequestStack $requestStack = null,
     ) {
     }
 
@@ -68,6 +75,10 @@ public function render(string|array $entryPoint, array $attributes = []): string
             $output .= "\n<link rel=\"stylesheet\" href=\"$url\">";
         }
 
+        if (class_exists(AddLinkHeaderListener::class) && $request = $this->requestStack?->getCurrentRequest()) {
+            $this->addWebLinkPreloads($request, $cssLinks);
+        }
+
         $scriptAttributes = $this->createAttributesString($attributes);
         $importMapJson = json_encode(['imports' => $importMap], \JSON_THROW_ON_ERROR | \JSON_PRETTY_PRINT | \JSON_UNESCAPED_SLASHES | \JSON_HEX_TAG);
         $output .= <<<HTML
@@ -131,4 +142,25 @@ private function createAttributesString(array $attributes): string
 
         return $attributeString;
     }
+
+    private function addWebLinkPreloads(Request $request, array $cssLinks): void
+    {
+        $cssPreloadLinks = array_map(fn ($url) => new Link('preload', $url), $cssLinks);
+
+        if (null === $linkProvider = $request->attributes->get('_links')) {
+            $request->attributes->set('_links', new GenericLinkProvider($cssPreloadLinks));
+
+            return;
+        }
+
+        if (!$linkProvider instanceof EvolvableLinkProviderInterface) {
+            return;
+        }
+
+        foreach ($cssPreloadLinks as $link) {
+            $linkProvider = $linkProvider->withLink($link);
+        }
+
+        $request->attributes->set('_links', $linkProvider);
+    }
 }
diff --git a/src/Symfony/Component/AssetMapper/Tests/ImportMap/ImportMapRendererTest.php b/src/Symfony/Component/AssetMapper/Tests/ImportMap/ImportMapRendererTest.php
@@ -15,6 +15,9 @@
 use Symfony\Component\Asset\Packages;
 use Symfony\Component\AssetMapper\ImportMap\ImportMapManager;
 use Symfony\Component\AssetMapper\ImportMap\ImportMapRenderer;
+use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\RequestStack;
+use Symfony\Component\WebLink\GenericLinkProvider;
 
 class ImportMapRendererTest extends TestCase
 {
@@ -130,4 +133,40 @@ private function createBasicImportMapManager(): ImportMapManager
 
         return $importMapManager;
     }
+
+    public function testItAddsPreloadLinks()
+    {
+        $importMapManager = $this->createMock(ImportMapManager::class);
+        $importMapManager->expects($this->once())
+            ->method('getImportMapData')
+            ->willReturn([
+                'app_js_preload' => [
+                    'path' => '/assets/app-preload-d1g35t.js',
+                    'type' => 'js',
+                    'preload' => true,
+                ],
+                'app_css_preload' => [
+                    'path' => '/assets/styles/app-preload-d1g35t.css',
+                    'type' => 'css',
+                    'preload' => true,
+                ],
+                'app_css_no_preload' => [
+                    'path' => '/assets/styles/app-nopreload-d1g35t.css',
+                    'type' => 'css',
+                ],
+            ]);
+
+        $request = Request::create('/foo');
+        $requestStack = new RequestStack();
+        $requestStack->push($request);
+
+        $renderer = new ImportMapRenderer($importMapManager, requestStack: $requestStack);
+        $renderer->render(['app']);
+
+        $linkProvider = $request->attributes->get('_links');
+        $this->assertInstanceOf(GenericLinkProvider::class, $linkProvider);
+        $this->assertCount(1, $linkProvider->getLinks());
+        $this->assertSame(['preload'], $linkProvider->getLinks()[0]->getRels());
+        $this->assertSame('/assets/styles/app-preload-d1g35t.css', $linkProvider->getLinks()[0]->getHref());
+    }
 }
diff --git a/src/Symfony/Component/AssetMapper/composer.json b/src/Symfony/Component/AssetMapper/composer.json
@@ -28,7 +28,8 @@
         "symfony/finder": "^5.4|^6.0|^7.0",
         "symfony/framework-bundle": "^6.4|^7.0",
         "symfony/http-foundation": "^5.4|^6.0|^7.0",
-        "symfony/http-kernel": "^5.4|^6.0|^7.0"
+        "symfony/http-kernel": "^5.4|^6.0|^7.0",
+        "symfony/web-link": "^5.4|^6.0|^7.0"
     },
     "conflict": {
         "symfony/framework-bundle": "<6.4"
