We're trying to configure our application to use json format by default and override the format for specific routes to be plain text (Prometheus metrics endpoint for example). Our expectation was that using the format parameter in the Route attribute would overwrite the format in the configuration defaults.

Configuration (routes.yaml):

controllers:
  resource:
    path: ../src/Controller/
    namespace: App\Controller
  type: attribute
  defaults:
    _format: json

Route attribute:

#[Route('/metrics', format: 'txt')]
public function metrics(): Response {
    return new Response(content: '# HELP');
}

When calling this route, the response contains the header Content-Type: application/json instead of the expected Content-Type: text/plain. We can work around this issue by explicitly setting the Content-Type header on the returned Response, but are wondering whether it is by design that the routes.yaml configuration overwrites the Route attribute format parameter.