[5.8] Fix fake dispatcher issue

Description:
Integration tests proof that it will work with both built-in session guard or any other custom guard whether it has a dispatcher or not.

Note : some build-in guards like Token guard does dispatch any events, hence there is no `setDispatcher ` method or any dispatcher on it.
So there are 2 types of guards.

which I think a contract (interface) is missing here, in order to mark the SessionGuard class or any other custom guard as an event dispatching guard, and enforce `setDispatcher` and `getDispatcher` methods on them.)

So the clunky `method_exists` check won't be needed.

Re-submit: #28131
fixed: #27451

src/Illuminate/Auth/AuthServiceProvider.php

@@ -23,6 +23,8 @@ public function register()
         $this->registerAccessGate();
 
         $this->registerRequestRebindHandler();
+
+        $this->registerEventRebindHandler();
     }
 
     /**
@@ -87,4 +89,19 @@ protected function registerRequestRebindHandler()
             });
         });
     }
+
+    /**
+     * Register a resolver for the 'events' rebinding.
+     *
+     * @return void
+     */
+    protected function registerEventRebindHandler()
+    {
+        $this->app->rebinding('events', function ($app, $dispatcher) {
+            $guard = $app['auth']->guard();
+            if (method_exists($guard, 'setDispatcher')) {
+                $guard->setDispatcher($dispatcher);
+            }
+        });
+    }
 }

tests/Integration/Auth/AuthenticationTest.php

@@ -4,16 +4,20 @@
 
 use Illuminate\Support\Str;
 use Illuminate\Auth\Events\Login;
+use Illuminate\Auth\SessionGuard;
+use Illuminate\Events\Dispatcher;
 use Orchestra\Testbench\TestCase;
 use Illuminate\Auth\Events\Failed;
 use Illuminate\Auth\Events\Logout;
+use Illuminate\Support\Facades\Auth;
 use Illuminate\Support\Facades\Event;
 use Illuminate\Auth\Events\Attempting;
 use Illuminate\Support\Facades\Schema;
 use Illuminate\Auth\EloquentUserProvider;
 use Illuminate\Auth\Events\Authenticated;
 use Illuminate\Database\Schema\Blueprint;
 use Illuminate\Auth\Events\OtherDeviceLogout;
+use Illuminate\Support\Testing\Fakes\EventFake;
 use Illuminate\Tests\Integration\Auth\Fixtures\AuthenticationTestUser;
 
 /**
@@ -245,4 +249,79 @@ public function test_auth_via_attempt_remembering()
 
         $this->assertNull($provider->retrieveByToken($user->id, $token));
     }
+
+    public function test_dispatcher_changes_if_there_is_one_on_the_auth_guard()
+    {
+        $this->assertInstanceOf(SessionGuard::class, $this->app['auth']->guard());
+        $this->assertInstanceOf(Dispatcher::class, $this->app['auth']->guard()->getDispatcher());
+
+        Event::fake();
+
+        $this->assertInstanceOf(SessionGuard::class, $this->app['auth']->guard());
+        $this->assertInstanceOf(EventFake::class, $this->app['auth']->guard()->getDispatcher());
+    }
+
+    public function test_dispatcher_changes_if_there_is_one_on_the_custom_auth_guard()
+    {
+        $this->app['config']['auth.guards.myGuard'] = [
+            'driver' => 'myCustomDriver',
+            'provider' => 'user',
+        ];
+
+        Auth::extend('myCustomDriver', function () {
+            return new MyCustomGuardStub();
+        });
+
+
+        $this->assertInstanceOf(MyCustomGuardStub::class, $this->app['auth']->guard('myGuard'));
+        $this->assertInstanceOf(Dispatcher::class, $this->app['auth']->guard()->getDispatcher());
+
+        Event::fake();
+
+        $this->assertInstanceOf(MyCustomGuardStub::class, $this->app['auth']->guard('myGuard'));
+        $this->assertInstanceOf(EventFake::class, $this->app['auth']->guard()->getDispatcher());
+    }
+
+
+    public function test_has_no_problem_if_there_is_no_dispatching_the_auth_custom_guard()
+    {
+        $this->app['config']['auth.guards.myGuard'] = [
+            'driver' => 'myCustomDriver',
+            'provider' => 'user',
+        ];
+
+        Auth::extend('myCustomDriver', function() {
+            return new MyDispatcherLessCustomGuardStub();
+        });
+
+        $this->assertInstanceOf(MyDispatcherLessCustomGuardStub::class, $this->app['auth']->guard('myGuard'));
+
+        Event::fake();
+
+        $this->assertInstanceOf(MyDispatcherLessCustomGuardStub::class, $this->app['auth']->guard('myGuard'));
+    }
+}
+
+class MyCustomGuardStub
+{
+    protected $events;
+
+    public function __construct()
+    {
+        $this->setDispatcher(new Dispatcher());
+    }
+
+    public function setDispatcher(Dispatcher $events)
+    {
+        $this->events = $events;
+    }
+
+    public function getDispatcher()
+    {
+        return $this->events;
+    }
 }
+
+class MyDispatcherLessCustomGuardStub
+{
+}