Move logic to Extension class

The gathering and execution of extenders can actually be done here
in the `Extension` class. This way, the `ExtensionManager` only
deals with the question of which extensions are enabled, the
`Extension` class actually extends the core application, and the
service provider simply calls a method, without having to know
about internals.

src/Extension/Extension.php

@@ -11,6 +11,8 @@
 
 namespace Flarum\Extension;
 
+use Flarum\Extend\Compat;
+use Illuminate\Contracts\Container\Container;
 use Illuminate\Contracts\Support\Arrayable;
 use Illuminate\Support\Arr;
 use Illuminate\Support\Str;
@@ -109,6 +111,28 @@ class Extension implements Arrayable
         $this->id = "$vendor-$package";
     }
 
+    public function extend(Container $app)
+    {
+        $bootstrapper = $this->getBootstrapperPath();
+
+        if (!file_exists($bootstrapper)) {
+            return;
+        }
+
+        $extenders = array_flatten((array) require $bootstrapper);
+
+        foreach ($extenders as $extender) {
+            // If an extension has not yet switched to the new bootstrap.php
+            // format, it might return a function (or more of them). We wrap
+            // these in a Compat extender to enjoy an unique interface.
+            if ($extender instanceof \Closure || is_string($extender)) {
+                $extender = new Compat($extender);
+            }
+
+            $extender($app, $this);
+        }
+    }
+
     /**
      * {@inheritdoc}
      */

src/Extension/ExtensionManager.php

@@ -20,6 +20,7 @@ use Flarum\Extension\Event\Enabling;
 use Flarum\Extension\Event\Uninstalled;
 use Flarum\Foundation\Application;
 use Flarum\Settings\SettingsRepositoryInterface;
+use Illuminate\Contracts\Container\Container;
 use Illuminate\Contracts\Events\Dispatcher;
 use Illuminate\Filesystem\Filesystem;
 use Illuminate\Support\Arr;
@@ -275,33 +276,15 @@ class ExtensionManager
     }
 
     /**
-     * Retrieve all extender instances of all enabled extensions.
+     * Call on all enabled extensions to extend the Flarum application.
      *
-     * @return Collection
+     * @param Container $app
      */
-    public function getActiveExtenders()
+    public function extend(Container $app)
     {
-        return $this->getEnabledExtensions()
-            ->flatMap(function (Extension $extension) {
-                $bootstrapper = $extension->getBootstrapperPath();
-
-                if ($this->filesystem->exists($bootstrapper)) {
-                    return array_map(function ($extender) use ($extension) {
-                        // If an extension has not yet switched to the new bootstrap.php
-                        // format, it might return a function (or more of them). We wrap
-                        // these in a Compat extender to enjoy an unique interface.
-                        if ($extender instanceof \Closure || is_string($extender)) {
-                            $extender = new Compat($extender);
-                        }
-
-                        return function ($app) use ($extension, $extender) {
-                            return $extender($app, $extension);
-                        };
-                    }, array_flatten((array) require $bootstrapper));
-                }
-
-                return [];
-            });
+        foreach ($this->getEnabledExtensions() as $extension) {
+            $extension->extend($app);
+        }
     }
 
     /**

src/Extension/ExtensionServiceProvider.php

@@ -24,11 +24,7 @@ class ExtensionServiceProvider extends AbstractServiceProvider
         $this->app->bind('flarum.extensions', ExtensionManager::class);
 
         $this->app->booting(function (Container $app) {
-            $extenders = $app->make('flarum.extensions')->getActiveExtenders();
-
-            foreach ($extenders as $extender) {
-                $extender($app);
-            }
+            $app->make('flarum.extensions')->extend($app);
         });
     }