make sure HEAD requests do not return a body

Slim/App.php

@@ -11,7 +11,6 @@
 use Exception;
 use Psr\Http\Message\UriInterface;
 use Slim\Exception\InvalidMethodException;
-use Slim\Http\Response;
 use Throwable;
 use Closure;
 use InvalidArgumentException;
@@ -27,7 +26,6 @@
 use Slim\Http\Headers;
 use Slim\Http\Body;
 use Slim\Http\Request;
-use Slim\Interfaces\Http\EnvironmentInterface;
 use Slim\Interfaces\RouteGroupInterface;
 use Slim\Interfaces\RouteInterface;
 use Slim\Interfaces\RouterInterface;
@@ -445,7 +443,8 @@ public function respond(ResponseInterface $response)
         }
 
         // Body
-        if (!$this->isEmptyResponse($response)) {
+        $request = $this->container->get('request');
+        if (!$this->isEmptyResponse($response) && !$this->isHeadRequest($request)) {
             $body = $response->getBody();
             if ($body->isSeekable()) {
                 $body->rewind();
@@ -614,7 +613,8 @@ protected function finalize(ResponseInterface $response)
         // stop PHP sending a Content-Type automatically
         ini_set('default_mimetype', '');
 
-        if ($this->isEmptyResponse($response)) {
+        $request = $this->container->get('request');
+        if ($this->isEmptyResponse($response) && !$this->isHeadRequest($request)) {
             return $response->withoutHeader('Content-Type')->withoutHeader('Content-Length');
         }
 
@@ -631,6 +631,11 @@ protected function finalize(ResponseInterface $response)
             }
         }
 
+        // clear the body if this is a HEAD request
+        if ($this->isHeadRequest($request)) {
+            return $response->withBody(new Body(fopen('php://temp', 'r+')));
+        }
+
         return $response;
     }
 
@@ -652,6 +657,18 @@ protected function isEmptyResponse(ResponseInterface $response)
         return in_array($response->getStatusCode(), [204, 205, 304]);
     }
 
+    /**
+     * Helper method to check if the current request is a HEAD request
+     *
+     * @param RequestInterface $request
+     *
+     * @return bool
+     */
+    protected function isHeadRequest(RequestInterface $request)
+    {
+        return strtoupper($request->getMethod()) === 'HEAD';
+    }
+
     /**
      * Call relevant handler from the Container if needed. If it doesn't exist,
      * then just re-throw.

tests/AppTest.php

@@ -9,6 +9,7 @@
 
 namespace Slim\Tests;
 
+use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
 use Psr\Http\Message\UriInterface;
 use Slim\App;
@@ -24,6 +25,7 @@
 use Slim\Http\Request;
 use Slim\Http\RequestBody;
 use Slim\Http\Response;
+use Slim\Http\StatusCode;
 use Slim\Http\Uri;
 use Slim\Router;
 use Slim\Tests\Assets\HeaderStack;
@@ -1515,37 +1517,72 @@ public function testInvokeSubRequestUsesResponseObject()
 
     // TODO: Test run()
     public function testRun()
+    {
+        $app = $this->getAppForTestingRunMethod();
+
+        ob_start();
+        $app->run();
+        $resOut = ob_get_clean();
+
+        $this->assertEquals('bar', (string)$resOut);
+    }
+
+    public function testRunReturnsEmptyResponseBodyWithHeadRequestMethod()
+    {
+        $app = $this->getAppForTestingRunMethod('HEAD');
+
+        ob_start();
+        $app->run();
+        $resOut = ob_get_clean();
+
+        $this->assertEquals('', (string)$resOut);
+    }
+
+    public function testRunReturnsEmptyResponseBodyWithGetRequestMethodInSilentMode()
+    {
+        $app = $this->getAppForTestingRunMethod();
+        $response = $app->run(true);
+
+        $this->assertEquals('bar', $response->getBody()->__toString());
+    }
+
+    public function testRunReturnsEmptyResponseBodyWithHeadRequestMethodInSilentMode()
+    {
+        $app = $this->getAppForTestingRunMethod('HEAD');
+        $response = $app->run(true);
+
+        $this->assertEquals('', $response->getBody()->__toString());
+    }
+
+    private function getAppForTestingRunMethod($method = 'GET')
     {
         $app = new App();
 
         // Prepare request and response objects
         $env = Environment::mock([
             'SCRIPT_NAME' => '/index.php',
             'REQUEST_URI' => '/foo',
-            'REQUEST_METHOD' => 'GET',
+            'REQUEST_METHOD' => $method,
         ]);
         $uri = Uri::createFromEnvironment($env);
         $headers = Headers::createFromEnvironment($env);
         $cookies = [];
         $serverParams = $env->all();
         $body = new Body(fopen('php://temp', 'r+'));
-        $req = new Request('GET', $uri, $headers, $cookies, $serverParams, $body);
-        $res = new Response();
+        $req = new Request($method, $uri, $headers, $cookies, $serverParams, $body);
+        $res = new Response(StatusCode::HTTP_OK, null, $body);
         $app->getContainer()['request'] = $req;
         $app->getContainer()['response'] = $res;
 
         $app->get('/foo', function ($req, $res) {
-            echo 'bar';
-        });
+            $res->getBody()->write('bar');
 
-        ob_start();
-        $app->run();
-        $resOut = ob_get_clean();
+            return $res;
+        });
 
-        $this->assertEquals('bar', (string)$resOut);
+        return $app;
     }
 
-
     public function testRespond()
     {
         $app = new App();
@@ -2326,6 +2363,34 @@ public function testIsEmptyResponseWithoutEmptyMethod()
         $this->assertTrue($result);
     }
 
+    public function testIsHeadRequestWithGetRequest()
+    {
+        $method = new \ReflectionMethod('Slim\App', 'isHeadRequest');
+        $method->setAccessible(true);
+
+        /** @var Request $request */
+        $request = $this->getMockBuilder(RequestInterface::class)->getMock();
+        $request->method('getMethod')
+            ->willReturn('get');
+
+        $result = $method->invoke(new App(), $request);
+        $this->assertFalse($result);
+    }
+
+    public function testIsHeadRequestWithHeadRequest()
+    {
+        $method = new \ReflectionMethod('Slim\App', 'isHeadRequest');
+        $method->setAccessible(true);
+
+        /** @var Request $request */
+        $request = $this->getMockBuilder(RequestInterface::class)->getMock();
+        $request->method('getMethod')
+            ->willReturn('head');
+
+        $result = $method->invoke(new App(), $request);
+        $this->assertTrue($result);
+    }
+
     public function testHandlePhpError()
     {
         $this->skipIfPhp70();