rpc.pre_response

The response has been built but not sent yet. Dispatched both for a result and for an error (in that case $service is null).

When it is dispatched

• After successful method execution (before rpc.post_execute).
• After an execution error (from rpc.error).
• On receipt of a notification or a request with $rpc.callback — with a placeholder response (null or {"async": true, "callback": …}); later, when the method runs, — once more with the real response.

Not dispatched for a cached response.

Built-in listeners

What can be changed

RpcResponse is immutable. To replace the response, set a new one through the request with a priority above -100000:

$event->rpcRequest->setResponse(new RpcResponse($event->rpcRequest->getId(), $newResult));

• Assigning $event->response does not change the response to the client (but this is exactly what rpc.post_response receives).
• Listeners with a priority above 1000 see the raw result object, below 1000 — an already normalized array.
• Replacement has no effect on the notification/callback placeholder.
• Do not stop propagation above -100000: the response will not be picked up.

Usage examples

Masking sensitive data

#[AsEventListener(RpcEvent::PRE_RESPONSE, priority: 500)]
final class MaskEmailListener
{
    public function __invoke(RpcPreResponseEvent $event): void
    {
        $result = $event->response->getResult();
        if ($event->response->getError() !== null || !is_array($result) || !isset($result['email'])) {
            return;
        }

        $result['email'] = preg_replace('/(?<=.).(?=[^@]*@)/', '*', $result['email']);
        $event->rpcRequest->setResponse(new RpcResponse($event->rpcRequest->getId(), $result));
    }
}

Other ideas

• logging responses (taking errors into account: $event->response->getError());
• adding service fields to the result for a specific API group;
• collecting response size metrics.