TASK: Widget view helper explicitly merge things

`replaceHttpResponse` is unsafe to use and has hard to tell behaviour.
Instead, we up-merge the headers explicitly

Neos.FluidAdaptor/Classes/Core/Widget/AbstractWidgetViewHelper.php

@@ -239,19 +239,41 @@ protected function initiateSubRequest()
             $subRequest->setControllerObjectName($this->widgetContext->getControllerObjectName());
             try {
                 $subResponse = $this->controller->processRequest($subRequest);
-
-                // We need to make sure to not merge content up into the parent ActionResponse because that _could_ break the parent response.
-                $content = $subResponse->getBody()->getContents();
-                $subResponse = $subResponse->withBody(Utils::streamFor(''));
             } catch (StopActionException $exception) {
                 $subResponse = $exception->response;
-                $this->controllerContext->getResponse()->replaceHttpResponse($subResponse);
-                throw $exception;
+                $parentResponse = $this->controllerContext->getResponse()->buildHttpResponse();
+
+                // transfer possible headers that have been set dynamically
+                foreach ($subResponse->getHeaders() as $name => $values) {
+                    $parentResponse = $parentResponse->withHeader($name, $values);
+                }
+                // if the status code is 200 we assume it's the default and will not overrule it
+                if ($subResponse->getStatusCode() !== 200) {
+                    $parentResponse = $parentResponse->withStatus($subResponse->getStatusCode());
+                }
+
+                if ($subResponse->getBody()->getSize() !== 0) {
+                    $parentResponse = $parentResponse->withBody($subResponse->getBody());
+                }
+
+                throw StopActionException::createForResponse($parentResponse, 'Intercepted from widget view helper.');
             } catch (ForwardException $exception) {
                 $subRequest = $exception->nextRequest;
                 continue;
             }
-            $this->controllerContext->getResponse()->replaceHttpResponse($subResponse);
+
+            // We need to make sure to not merge content up into the parent ActionResponse because that _could_ break the parent response.
+            $content = $subResponse->getBody()->getContents();
+
+            // hacky, but part of the deal. We have to manipulate the global response to redirect for example.
+            // transfer possible headers that have been set dynamically
+            foreach ($subResponse->getHeaders() as $name => $values) {
+                $this->controllerContext->getResponse()->setHttpHeader($name, $values);
+            }
+            // if the status code is 200 we assume it's the default and will not overrule it
+            if ($subResponse->getStatusCode() !== 200) {
+                $this->controllerContext->getResponse()->setStatusCode($subResponse->getStatusCode());
+            }
         }
 
         return $content;