Resolve extenders from ExtensionManager

Loading the activated extensions now means retrieving an array of
extenders (classes that implement a certain type of extension of a core
feature in Flarum).

For now, the only existing extender is the Compat extender which is used
to handle old-style bootstrappers that simply return a closure that
receives all of its dependencies via auto injection.

In the future, extensions will be able to return an array of extender
instances from their bootstrapper instead. These extender classes will
be implemented in the next step.

src/Extend/Compat.php

@@ -0,0 +1,38 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Extend;
+
+use Illuminate\Contracts\Container\Container;
+
+/**
+ * This class is used to wrap old bootstrap.php closures (as used in versions up
+ * to 0.1.0-beta7) in the new Extender format.
+ *
+ * This gives extensions the chance to work with the new API without making any
+ * changes, and have some time to convert to the pure usage of extenders.
+ *
+ * @deprecated
+ */
+class Compat implements Extender
+{
+    protected $callback;
+
+    public function __construct($callback)
+    {
+        $this->callback = $callback;
+    }
+
+    public function apply(Container $container)
+    {
+        $container->call($this->callback);
+    }
+}

src/Extend/Extender.php

@@ -0,0 +1,19 @@
+<?php
+
+/*
+ * This file is part of Flarum.
+ *
+ * (c) Toby Zerner <toby.zerner@gmail.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Flarum\Extend;
+
+use Illuminate\Contracts\Container\Container;
+
+interface Extender
+{
+    public function apply(Container $container);
+}

src/Extension/Extension.php

@@ -231,6 +231,11 @@ class Extension implements Arrayable
         return $this->path;
     }
 
+    public function getBootstrapperPath()
+    {
+        return "{$this->path}/bootstrap.php";
+    }
+
     /**
      * Tests whether the extension has assets.
      *

src/Extension/ExtensionManager.php

@@ -12,6 +12,7 @@
 namespace Flarum\Extension;
 
 use Flarum\Database\Migrator;
+use Flarum\Extend\Compat;
 use Flarum\Extension\Event\Disabled;
 use Flarum\Extension\Event\Disabling;
 use Flarum\Extension\Event\Enabled;
@@ -273,21 +274,30 @@ class ExtensionManager
     }
 
     /**
-     * Loads all bootstrap.php files of the enabled extensions.
+     * Retrieve all extender instances of all enabled extensions.
      *
      * @return Collection
      */
-    public function getEnabledBootstrappers()
+    public function getActiveExtenders()
     {
-        $bootstrappers = new Collection;
+        return $this->getEnabledExtensions()
+            ->flatMap(function (Extension $extension) {
+                $bootstrapper = $extension->getBootstrapperPath();
+                if ($this->filesystem->exists($bootstrapper)) {
+                    $extenders = require $bootstrapper;
 
-        foreach ($this->getEnabledExtensions() as $extension) {
-            if ($this->filesystem->exists($file = $extension->getPath().'/bootstrap.php')) {
-                $bootstrappers->push($file);
-            }
-        }
+                    if (is_array($extenders)) {
+                        return $extenders;
+                    }
 
-        return $bootstrappers;
+                    // Assume that the extension has not yet switched to the new
+                    // bootstrap.php format, and wrap the callback in a Compat
+                    // extender.
+                    return [new Compat($extenders)];
+                } else {
+                    return [];
+                }
+            });
     }
 
     /**

src/Extension/ExtensionServiceProvider.php

@@ -12,6 +12,7 @@
 namespace Flarum\Extension;
 
 use Flarum\Foundation\AbstractServiceProvider;
+use Illuminate\Contracts\Container\Container;
 
 class ExtensionServiceProvider extends AbstractServiceProvider
 {
@@ -22,13 +23,14 @@ class ExtensionServiceProvider extends AbstractServiceProvider
     {
         $this->app->bind('flarum.extensions', ExtensionManager::class);
 
-        $bootstrappers = $this->app->make('flarum.extensions')->getEnabledBootstrappers();
+        $this->app->booting(function (Container $app) {
+            /** @var \Flarum\Extend\Extender[] $extenders */
+            $extenders = $app->make('flarum.extensions')->getActiveExtenders();
 
-        foreach ($bootstrappers as $file) {
-            $bootstrapper = require $file;
-
-            $this->app->call($bootstrapper);
-        }
+            foreach ($extenders as $extender) {
+                $extender->apply($app);
+            }
+        });
     }
 
     /**