Ensure that MiddlewarePipes are called as callables if an error is present

src/Dispatch.php

@@ -76,6 +76,11 @@ public function __invoke(
             $this->setResponsePrototype($response);
         }
 
+        // Handle middleware pipes as callables if an $err is present
+        if ($route->handler instanceof MiddlewarePipe && null !== $err) {
+            return $this->dispatchCallableMiddleware($route->handler, $next, $request, $response, $err);
+        }
+
         if ($route->handler instanceof ServerMiddlewareInterface) {
             return $this->dispatchInteropMiddleware($route->handler, $next, $request);
         }

test/DispatchTest.php

@@ -441,6 +441,104 @@ public function testInvokingWithInteropMiddlewareDispatchesIt()
         );
     }
 
+    public function errorProvider()
+    {
+        yield 'exception' => [new \Exception('expected')];
+        yield 'derivative-exception' => [new RuntimeException('expected')];
+        if (version_compare(\PHP_VERSION, '7.0', 'gte')) {
+            yield 'throwable' => [new \Error('expected')];
+        }
+    }
+
+    /**
+     * @dataProvider errorProvider
+     */
+    public function testInvokingWithMiddlewarePipeAndErrorDispatchesNextErrorMiddleware($error)
+    {
+        $request  = $this->prophesize(ServerRequestInterface::class)->reveal();
+        $response = $this->prophesize(ResponseInterface::class)->reveal();
+        $expected = $this->prophesize(ResponseInterface::class)->reveal();
+
+        $next = $this->prophesize(Next::class);
+        $next->willImplement(DelegateInterface::class);
+        $next
+            ->__invoke(
+                $request,
+                $this->response->reveal(),
+                $error
+            )
+            ->willReturn($expected);
+
+        $middleware = $this->prophesize(MiddlewarePipe::class);
+        $middleware
+            ->__invoke(
+                Argument::type(ServerRequestInterface::class),
+                Argument::type(ResponseInterface::class),
+                Argument::type('callable')
+            )
+            ->shouldNotBeCalled();
+        $middleware
+            ->process(
+                Argument::type(ServerRequestInterface::class),
+                Argument::type(DelegateInterface::class)
+            )
+            ->shouldNotBeCalled();
+
+        $route = new Route('/foo', $middleware->reveal());
+
+        $dispatch = new Dispatch();
+
+        $this->assertSame(
+            $expected,
+            $dispatch($route, $error, $request, $this->response->reveal(), $next->reveal())
+        );
+    }
+
+    public function testInvokingWithMiddlewarePipeAndNoErrorDispatchesAsInteropMiddleware()
+    {
+        $request  = $this->prophesize(ServerRequestInterface::class)->reveal();
+        $response = $this->prophesize(ResponseInterface::class)->reveal();
+
+        $next = $this->prophesize(Next::class);
+        $next->willImplement(DelegateInterface::class);
+        $next
+            ->__invoke(
+                Argument::type(ServerRequestInterface::class),
+                Argument::type(ResponseInterface::class)
+            )
+            ->shouldNotBeCalled();
+        $next
+            ->process(Argument::type(ServerRequestInterface::class))
+            ->shouldNotBeCalled();
+
+        $middleware = $this->prophesize(MiddlewarePipe::class);
+        $middleware
+            ->__invoke(
+                Argument::type(ServerRequestInterface::class),
+                Argument::type(ResponseInterface::class),
+                Argument::type('callable')
+            )
+            ->shouldNotBeCalled();
+        $middleware
+            ->hasResponsePrototype()
+            ->willReturn(true);
+        $middleware
+            ->process(
+                Argument::type(ServerRequestInterface::class),
+                Argument::type(DelegateInterface::class)
+            )
+            ->willReturn($response);
+
+        $route = new Route('/foo', $middleware->reveal());
+
+        $dispatch = new Dispatch();
+
+        $this->assertSame(
+            $response,
+            $dispatch($route, null, $request, $this->response->reveal(), $next->reveal())
+        );
+    }
+
     /**
      * @group http-interop
      */