Return Exceptions as JSON reponse for JSON request

config/services.yaml

@@ -96,6 +96,10 @@ services:
             $defaultLocale: "%locale%"
             $supportedLocales: "%supported_locales%"
 
+    App\EventListener\JsonExceptionListener:
+        tags:
+            - { name: 'kernel.event_listener', event: 'kernel.exception' }
+
     App\Handler\:
         resource: '../src/Handler/*'
         public: true

src/EventListener/JsonResponseExceptionListener.php

@@ -0,0 +1,24 @@
+<?php
+
+namespace App\EventListener;
+
+use Symfony\Component\HttpFoundation\JsonResponse;
+use Symfony\Component\HttpKernel\Event\ExceptionEvent;
+use Symfony\Component\HttpKernel\Exception\HttpExceptionInterface;
+
+class JsonResponseExceptionListener
+{
+    public function onKernelException(ExceptionEvent $event)
+    {
+        $request = $event->getRequest();
+
+        if (
+            $request->headers->get('Accept') === 'application/json' ||
+            $request->headers->get('Content-Type') === 'application/json'
+        ) {
+            $exception = $event->getThrowable();
+            $statusCode = $exception instanceof HttpExceptionInterface ? $exception->getStatusCode() : 500;
+            $event->setResponse(new JsonResponse(['error' => $exception->getMessage()], $statusCode));
+        }
+    }
+}