Refactor frontend code to allow for extension of assets

- Simpler class naming:
    Frontend\CompilerFactory → Frontend\Assets
    Frontend\HtmlDocumentFactory → Frontend\Frontend
    Frontend\HtmlDocument → Frontend\Document

- Remove AssetInterface and simply collect callbacks in Frontend\Assets
  instead

- Remove ContentInterface because it serves no purpose (never type-
  hinted or type-checked)

- Commit and add asset URLs to the Document via a content callback
  instead of in the Document factory class itself

- Add translations and locale assets to Assets separate to the assets
  factory, as non-forum/admin asset bundles probably won't want them

- Update Frontend Extender to allow the creation of new asset bundles

- Make custom LESS validation listener a standalone class instead of
  extending RecompileFrontendAssets

src/Admin/AdminServiceProvider.php

@@ -14,6 +14,9 @@
 use Flarum\Event\ConfigureMiddleware;
 use Flarum\Foundation\AbstractServiceProvider;
 use Flarum\Foundation\Application;
+use Flarum\Frontend\AddLocaleAssets;
+use Flarum\Frontend\AddTranslations;
+use Flarum\Frontend\Compiler\Source\SourceCollector;
 use Flarum\Frontend\RecompileFrontendAssets;
 use Flarum\Http\Middleware as HttpMiddleware;
 use Flarum\Http\RouteCollection;
@@ -62,17 +65,31 @@ public function register()
             $pipe->pipe(new HttpMiddleware\DispatchRoute($this->app->make('flarum.admin.routes')));
         });
 
-        $this->app->bind('flarum.admin.assets', function () {
-            return $this->app->make('flarum.frontend.assets.defaults')('admin');
+        $this->app->bind('flarum.assets.admin', function () {
+            /** @var \Flarum\Frontend\Assets $assets */
+            $assets = $this->app->make('flarum.assets.factory')('admin');
+
+            $assets->js(function (SourceCollector $sources) {
+                $sources->addFile(__DIR__.'/../../js/dist/admin.js');
+            });
+
+            $assets->css(function (SourceCollector $sources) {
+                $sources->addFile(__DIR__.'/../../less/admin.less');
+            });
+
+            $this->app->make(AddTranslations::class)->forFrontend('admin')->to($assets);
+            $this->app->make(AddLocaleAssets::class)->to($assets);
+
+            return $assets;
         });
 
-        $this->app->bind('flarum.admin.frontend', function () {
-            $view = $this->app->make('flarum.frontend.view.defaults')('admin');
+        $this->app->bind('flarum.frontend.admin', function () {
+            /** @var \Flarum\Frontend\Frontend $frontend */
+            $frontend = $this->app->make('flarum.frontend.factory')('admin');
 
-            $view->setAssets($this->app->make('flarum.admin.assets'));
-            $view->add($this->app->make(Content\AdminPayload::class));
+            $frontend->content($this->app->make(Content\AdminPayload::class));
 
-            return $view;
+            return $frontend;
         });
     }
 
@@ -87,7 +104,7 @@ public function boot()
 
         $this->app->make('events')->subscribe(
             new RecompileFrontendAssets(
-                $this->app->make('flarum.admin.assets'),
+                $this->app->make('flarum.assets.admin'),
                 $this->app->make('flarum.locales')
             )
         );

src/Admin/Content/AdminPayload.php

@@ -12,16 +12,15 @@
 namespace Flarum\Admin\Content;
 
 use Flarum\Extension\ExtensionManager;
-use Flarum\Frontend\Content\ContentInterface;
-use Flarum\Frontend\HtmlDocument;
+use Flarum\Frontend\Document;
 use Flarum\Group\Permission;
 use Flarum\Settings\Event\Deserializing;
 use Flarum\Settings\SettingsRepositoryInterface;
 use Illuminate\Contracts\Events\Dispatcher;
 use Illuminate\Database\ConnectionInterface;
 use Psr\Http\Message\ServerRequestInterface as Request;
 
-class AdminPayload implements ContentInterface
+class AdminPayload
 {
     /**
      * @var SettingsRepositoryInterface
@@ -52,7 +51,7 @@ public function __construct(SettingsRepositoryInterface $settings, ExtensionMana
         $this->events = $events;
     }
 
-    public function __invoke(HtmlDocument $document, Request $request)
+    public function __invoke(Document $document, Request $request)
     {
         $settings = $this->settings->all();
 

src/Extend/Frontend.php

@@ -12,9 +12,9 @@
 namespace Flarum\Extend;
 
 use Flarum\Extension\Extension;
-use Flarum\Frontend\Asset\ExtensionAssets;
-use Flarum\Frontend\CompilerFactory;
-use Flarum\Frontend\HtmlDocumentFactory;
+use Flarum\Frontend\Assets;
+use Flarum\Frontend\Compiler\Source\SourceCollector;
+use Flarum\Frontend\RecompileFrontendAssets;
 use Flarum\Http\RouteHandlerFactory;
 use Illuminate\Contracts\Container\Container;
 
@@ -77,16 +77,42 @@ private function registerAssets(Container $container, string $moduleName)
             return;
         }
 
-        $container->resolving(
-            "flarum.$this->frontend.assets",
-            function (CompilerFactory $assets) use ($moduleName) {
-                $assets->add(function () use ($moduleName) {
-                    return new ExtensionAssets(
-                        $moduleName, $this->css, $this->js
-                    );
+        $abstract = 'flarum.assets.'.$this->frontend;
+
+        $container->resolving($abstract, function (Assets $assets) use ($moduleName) {
+            if ($this->js) {
+                $assets->js(function (SourceCollector $sources) use ($moduleName) {
+                    $sources->addString(function () {
+                        return 'var module={}';
+                    });
+                    $sources->addFile($this->js);
+                    $sources->addString(function () use ($moduleName) {
+                        return "flarum.extensions['$moduleName']=module.exports";
+                    });
                 });
             }
-        );
+
+            if ($this->css) {
+                $assets->css(function (SourceCollector $sources) {
+                    foreach ($this->css as $path) {
+                        $sources->addFile($path);
+                    }
+                });
+            }
+        });
+
+        if (! $container->bound($abstract)) {
+            $container->bind($abstract, function (Container $container) {
+                return $container->make('flarum.assets.factory')($this->frontend);
+            });
+
+            $container->make('events')->subscribe(
+                new RecompileFrontendAssets(
+                    $container->make($abstract),
+                    $container->make('flarum.locales')
+                )
+            );
+        }
     }
 
     private function registerRoutes(Container $container)
@@ -114,13 +140,13 @@ private function registerContent(Container $container)
 
         $container->resolving(
             "flarum.$this->frontend.frontend",
-            function (HtmlDocumentFactory $view, Container $container) {
+            function (Frontend $frontend, Container $container) {
                 foreach ($this->content as $content) {
                     if (is_string($content)) {
                         $content = $container->make($content);
                     }
 
-                    $view->add($content);
+                    $frontend->content($content);
                 }
             }
         );

src/Forum/Content/AssertRegistered.php

@@ -11,16 +11,15 @@
 
 namespace Flarum\Forum\Content;
 
-use Flarum\Frontend\Content\ContentInterface;
-use Flarum\Frontend\HtmlDocument;
+use Flarum\Frontend\Document;
 use Flarum\User\AssertPermissionTrait;
 use Psr\Http\Message\ServerRequestInterface as Request;
 
-class AssertRegistered implements ContentInterface
+class AssertRegistered
 {
     use AssertPermissionTrait;
 
-    public function __invoke(HtmlDocument $document, Request $request)
+    public function __invoke(Document $document, Request $request)
     {
         $this->assertRegistered($request->getAttribute('actor'));
     }

src/Forum/Content/Discussion.php

@@ -12,15 +12,14 @@
 namespace Flarum\Forum\Content;
 
 use Flarum\Api\Client;
-use Flarum\Frontend\Content\ContentInterface;
-use Flarum\Frontend\HtmlDocument;
+use Flarum\Frontend\Document;
 use Flarum\Http\Exception\RouteNotFoundException;
 use Flarum\Http\UrlGenerator;
 use Flarum\User\User;
 use Illuminate\Contracts\View\Factory;
 use Psr\Http\Message\ServerRequestInterface as Request;
 
-class Discussion implements ContentInterface
+class Discussion
 {
     /**
      * @var Client
@@ -49,7 +48,7 @@ public function __construct(Client $api, UrlGenerator $url, Factory $view)
         $this->view = $view;
     }
 
-    public function __invoke(HtmlDocument $document, Request $request)
+    public function __invoke(Document $document, Request $request)
     {
         $queryParams = $request->getQueryParams();
         $page = max(1, array_get($queryParams, 'page'));

src/Forum/Content/Index.php

@@ -13,13 +13,12 @@
 
 use Flarum\Api\Client;
 use Flarum\Api\Controller\ListDiscussionsController;
-use Flarum\Frontend\Content\ContentInterface;
-use Flarum\Frontend\HtmlDocument;
+use Flarum\Frontend\Document;
 use Flarum\User\User;
 use Illuminate\Contracts\View\Factory;
 use Psr\Http\Message\ServerRequestInterface as Request;
 
-class Index implements ContentInterface
+class Index
 {
     /**
      * @var Client
@@ -41,10 +40,7 @@ public function __construct(Client $api, Factory $view)
         $this->view = $view;
     }
 
-    /**
-     * {@inheritdoc}
-     */
-    public function __invoke(HtmlDocument $document, Request $request)
+    public function __invoke(Document $document, Request $request)
     {
         $queryParams = $request->getQueryParams();