class DefaultExceptionSubscriber

class DefaultExceptionSubscriber extends SerializationDefaultExceptionSubscriber {
    
    /**
     * {@inheritdoc}
     */
    protected static function getPriority() {
        return parent::getPriority() + 25;
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getHandledFormats() {
        return [
            'api_json',
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function onException(ExceptionEvent $event) {
        if (!$this->isJsonApiExceptionEvent($event)) {
            return;
        }
        if (($exception = $event->getThrowable()) && !$exception instanceof HttpException) {
            $exception = new HttpException(500, $exception->getMessage(), $exception);
            $event->setThrowable($exception);
        }
        $this->setEventResponse($event, $exception->getStatusCode());
    }
    
    /**
     * {@inheritdoc}
     */
    protected function setEventResponse(ExceptionEvent $event, $status) {
        
        /** @var \Symfony\Component\HttpKernel\Exception\HttpException $exception */
        $exception = $event->getThrowable();
        $document = new JsonApiDocumentTopLevel(new ErrorCollection([
            $exception,
        ]), new NullIncludedData(), new LinkCollection([]));
        if ($event->getRequest()
            ->isMethodCacheable()) {
            $response = new CacheableResourceResponse($document, $exception->getStatusCode(), $exception->getHeaders());
            $response->addCacheableDependency($exception);
        }
        else {
            $response = new ResourceResponse($document, $exception->getStatusCode(), $exception->getHeaders());
        }
        $event->setResponse($response);
    }
    
    /**
     * Check if the error should be formatted using JSON:API.
     *
     * The JSON:API format is supported if the format is explicitly set or the
     * request is for a known JSON:API route.
     *
     * @param \Symfony\Component\HttpKernel\Event\ExceptionEvent $exception_event
     *   The exception event.
     *
     * @return bool
     *   TRUE if it needs to be formatted using JSON:API. FALSE otherwise.
     */
    protected function isJsonApiExceptionEvent(ExceptionEvent $exception_event) {
        $request = $exception_event->getRequest();
        $parameters = $request->attributes
            ->all();
        return $request->getRequestFormat() === 'api_json' || (bool) Routes::getResourceTypeNameFromParameters($parameters);
    }

}