[5.5] Ability to build a response using a fallback route name

src/Illuminate/Routing/Router.php

@@ -572,20 +572,7 @@ public function dispatch(Request $request)
      */
     public function dispatchToRoute(Request $request)
     {
-        // First we will find a route that matches this request. We will also set the
-        // route resolver on the request so middlewares assigned to the route will
-        // receive access to this route instance for checking of the parameters.
-        $route = $this->findRoute($request);
-
-        $request->setRouteResolver(function () use ($route) {
-            return $route;
-        });
-
-        $this->events->dispatch(new Events\RouteMatched($route, $request));
-
-        $response = $this->runRouteWithinStack($route, $request);
-
-        return $this->prepareResponse($request, $response);
+        return $this->buildResponse($request, $this->findRoute($request));
     }
 
     /**
@@ -603,6 +590,26 @@ protected function findRoute($request)
         return $route;
     }
 
+    /**
+     * Return the response for the given route.
+     *
+     * @param  Route  $route
+     * @param  Request  $request
+     * @return mixed
+     */
+    protected function buildResponse(Request $request, Route $route)
+    {
+        $request->setRouteResolver(function () use ($route) {
+            return $route;
+        });
+
+        $this->events->dispatch(new Events\RouteMatched($route, $request));
+
+        return $this->prepareResponse($request,
+            $this->runRouteWithinStack($route, $request)
+        );
+    }
+
     /**
      * Run the given route within a Stack "onion" instance.
      *
@@ -1102,6 +1109,19 @@ public function auth()
         $this->post('password/reset', 'Auth\ResetPasswordController@reset');
     }
 
+    /**
+     * Return a response out of the given route.
+     *
+     * @param  string  $name
+     * @return mixed
+     */
+    public function respondWith($name)
+    {
+        return $this->buildResponse($this->currentRequest,
+            tap($this->routes->getByName($name))->bind($this->currentRequest)
+        );
+    }
+
     /**
      * Set the unmapped global resource parameters to singular.
      *

tests/Integration/Routing/FallbackRouteTest.php

@@ -72,6 +72,20 @@ public function test_no_routes()
         $this->assertEquals(404, $this->get('/non-existing')->getStatusCode());
     }
 
+    public function test_respond_with_named_fallback_route()
+    {
+        Route::fallback(function () {
+            return response('fallback', 404);
+        })->name('testFallbackRoute');
+
+        Route::get('one', function () {
+            return Route::respondWith('testFallbackRoute');
+        });
+
+        $this->assertContains('fallback', $this->get('/non-existing')->getContent());
+        $this->assertContains('fallback', $this->get('/one')->getContent());
+    }
+
     public function test_no_fallbacks()
     {
         Route::get('one', function () {