Support Responsable objects.

This is the foundation for allowing objects to be converted into full
HTTP responses, allowing more fluent API packages to be built in the
future.

src/Illuminate/Contracts/Support/Responsable.php

@@ -0,0 +1,13 @@
+<?php
+
+namespace Illuminate\Contracts\Support;
+
+interface Responsable
+{
+    /**
+     * Create an HTTP response that represents the object.
+     *
+     * @return \Illuminate\Http\Response
+     */
+    public function toResponse();
+}

src/Illuminate/Routing/Pipeline.php

@@ -71,7 +71,8 @@ protected function carry()
      */
     protected function handleException($passable, Exception $e)
     {
-        if (! $this->container->bound(ExceptionHandler::class) || ! $passable instanceof Request) {
+        if (! $this->container->bound(ExceptionHandler::class) ||
+            ! $passable instanceof Request) {
             throw $e;
         }
 

src/Illuminate/Routing/Router.php

@@ -15,6 +15,7 @@
 use Illuminate\Contracts\Support\Jsonable;
 use Illuminate\Contracts\Events\Dispatcher;
 use Illuminate\Contracts\Support\Arrayable;
+use Illuminate\Contracts\Support\Responsable;
 use Illuminate\Contracts\Routing\BindingRegistrar;
 use Psr\Http\Message\ResponseInterface as PsrResponseInterface;
 use Illuminate\Contracts\Routing\Registrar as RegistrarContract;
@@ -620,6 +621,8 @@ public static function prepareResponse($request, $response)
     {
         if ($response instanceof PsrResponseInterface) {
             $response = (new HttpFoundationFactory)->createResponse($response);
+        } elseif ($response instanceof Responsable) {
+            $response = $response->toResponse();
         } elseif (! $response instanceof SymfonyResponse &&
                    ($response instanceof Arrayable ||
                     $response instanceof Jsonable ||

tests/Integration/Routing/ResponsableTest.php

@@ -0,0 +1,33 @@
+<?php
+
+use Orchestra\Testbench\TestCase;
+use Illuminate\Support\Facades\Route;
+use Illuminate\Contracts\Support\Responsable;
+
+/**
+ * @group integration
+ */
+class ResponsableTest extends TestCase
+{
+    public function test_responsable_objects_are_rendered()
+    {
+        Route::get('/responsable', function () {
+            return new TestResponsableResponse;
+        });
+
+        $response = $this->get('/responsable');
+
+        $this->assertEquals(201, $response->status());
+        $this->assertEquals('Taylor', $response->headers->get('X-Test-Header'));
+        $this->assertEquals('hello world', $response->getContent());
+    }
+}
+
+
+class TestResponsableResponse implements Responsable
+{
+    public function toResponse()
+    {
+        return response('hello world', 201, ['X-Test-Header' => 'Taylor']);
+    }
+}