Return the original response if the body size has changed.

- Per @ezimuel, when the original response body has been written to,
  `FinalHandler` was still returning the 404 response. This patch
  ensures that if the body size changes, the response will still be
  returned.

src/FinalHandler.php

@@ -19,6 +19,13 @@
  */
 class FinalHandler
 {
+    /**
+     * Original response body size.
+     *
+     * @var int
+     */
+    private $bodySize = 0;
+
     /**
      * @var array
      */
@@ -39,6 +46,10 @@ public function __construct(array $options = [], ResponseInterface $response = n
     {
         $this->options  = $options;
         $this->response = $response;
+
+        if ($response) {
+            $this->bodySize = $response->getBody()->getSize();
+        }
     }
 
     /**
@@ -73,6 +84,16 @@ public function __invoke(RequestInterface $request, ResponseInterface $response,
             return $response;
         }
 
+        // If the response passed is the same as the one at instantiation,
+        // check to see if the body size has changed; if it has, return
+        // the response, as the message body has been written to.
+        if ($this->response
+            && $this->response === $response
+            && $this->bodySize !== $response->getBody()->getSize()
+        ) {
+            return $response;
+        }
+
         return $this->create404($request, $response);
     }
 

test/FinalHandlerTest.php

@@ -122,6 +122,9 @@ public function test404ResponseIncludesOriginalRequestUri()
         $this->assertContains($originalUrl, (string) $response->getBody());
     }
 
+    /**
+     * @group 12
+     */
     public function testReturnsResponseIfItDoesNotMatchResponsePassedToConstructor()
     {
         $psrResponse = new PsrResponse();
@@ -132,4 +135,19 @@ public function testReturnsResponseIfItDoesNotMatchResponsePassedToConstructor()
         $result = $final(new Request(new PsrRequest()), $passedResponse);
         $this->assertSame($passedResponse, $result);
     }
+
+    /**
+     * @group 12
+     */
+    public function testReturnsResponseIfBodyLengthHasChanged()
+    {
+        $psrResponse = new PsrResponse();
+        $response    = new Response($psrResponse);
+        $final       = new FinalHandler([], $response);
+
+        $response->write('return this response');
+
+        $result = $final(new Request(new PsrRequest()), $response);
+        $this->assertSame($response, $result);
+    }
 }