Frontend refactor (#1471)

Refactor Frontend + Asset code

- Use Laravel's Filesystem component for asset IO, meaning theoretically
  assets should be storable on S3 etc.

- More reliable checking for asset recompilation when debug mode is on,
  so you don't have to constantly delete the compiled assets to force
  a recompile. Should also fix issues with locale JS files being
  recompiled with the same name and cached.

- Remove JavaScript minification, because it will be done by Webpack
  (exception is for the TextFormatter JS).

- Add support for JS sourcemaps.

- Separate frontend view and assets completely. This is an important
  distinction because frontend assets are compiled independent of a
  request, whereas putting together a view depends on a request.

- Bind frontend view/asset factory instances to the container (in
  service providers) rather than subclassing. Asset and content
  populators can be added to these factories – these are simply objects
  that populate the asset compilers or the view with information.

- Add RouteHandlerFactory functions that make it easy to hook up a
  frontend controller with a frontend instance ± some content.

- Remove the need for "nojs"

- Fix cache:clear command

- Recompile assets when settings/enabled extensions change

framework/core/src/Extend/Assets.php

@@ -12,29 +12,37 @@
 namespace Flarum\Extend;
 
 use Flarum\Extension\Extension;
-use Flarum\Frontend\Event\Rendering;
+use Flarum\Frontend\Asset\ExtensionAssets;
+use Flarum\Frontend\CompilerFactory;
 use Illuminate\Contracts\Container\Container;
-use Illuminate\Events\Dispatcher;
 
 class Assets implements ExtenderInterface
 {
-    protected $appName;
+    protected $frontend;
 
-    protected $assets = [];
+    protected $css = [];
     protected $js;
 
-    public function __construct($appName)
+    public function __construct($frontend)
     {
-        $this->appName = $appName;
+        $this->frontend = $frontend;
     }
 
-    public function asset($path)
+    public function css($path)
     {
-        $this->assets[] = $path;
+        $this->css[] = $path;
 
         return $this;
     }
 
+    /**
+     * @deprecated
+     */
+    public function asset($path)
+    {
+        return $this->css($path);
+    }
+
     public function js($path)
     {
         $this->js = $path;
@@ -44,35 +52,13 @@ class Assets implements ExtenderInterface
 
     public function __invoke(Container $container, Extension $extension = null)
     {
-        $container->make(Dispatcher::class)->listen(
-            Rendering::class,
-            function (Rendering $event) use ($extension) {
-                if (! $this->matches($event)) {
-                    return;
-                }
-
-                $event->addAssets($this->assets);
-
-                if ($this->js) {
-                    $event->view->getJs()->addString(function () use ($extension) {
-                        $name = $extension->getId();
-
-                        return 'var module={};'.file_get_contents($this->js).";\nflarum.extensions['$name']=module.exports";
-                    });
-                }
+        $container->resolving(
+            "flarum.$this->frontend.assets",
+            function (CompilerFactory $assets) use ($extension) {
+                $assets->add(function () use ($extension) {
+                    return new ExtensionAssets($extension, $this->css, $this->js);
+                });
             }
         );
     }
-
-    private function matches(Rendering $event)
-    {
-        switch ($this->appName) {
-            case 'admin':
-                return $event->isAdmin();
-            case 'forum':
-                return $event->isForum();
-            default:
-                return false;
-        }
-    }
 }