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For complicated and unpleasant reasons[*], I want to embed entity data from the JSONAPI module inside JSON returned from a REST module resource.

I am trying to do this by making an HTTP subrequest to the JSONAPI module route within the REST module resource class.

Like this:

    $kernel = \Drupal::service('http_kernel');

    $current_request = \Drupal::request();

    $request = Request::create('/jsonapi/paragraph/' . $paragraph->bundle() . '/' . $paragraph->uuid->value);
    $request->setSession($current_request->getSession());

    $response = $kernel->handle($request, HttpKernelInterface::SUB_REQUEST);
    $json = $response->getContent();
    $data = json_decode($json, TRUE);

I get the data I want and it's great!

However, the main request to the REST resource endpoint crashes with this:

Symfony\Component\Serializer\Exception\NotEncodableValueException: Serialization for the format "api_json" is not supported. in Symfony\Component\Serializer\Serializer->serialize() (line 112 of /var/www/vendor/symfony/serializer/Serializer.php).

This is because in Drupal\rest\EventSubscriber\ResourceResponseSubscriber->getResponseFormat(), $route = $route_match->getRouteObject(); is the JSONAPI module route from the subrequest, and not the route from the main request.

What am I doing wrong with my subrequest?

[*] Enormous amount of custom code powering a REST resource for a decoupled front end. I want to change it to using JSONAPI but it's a massive change with huge repercussions on the frontend. To change over incrementally to JSONAPI, I want to switch some paragraph types to the JSONAPI format. Could call the JSONAPI module's PHP code directly, but that's not a public API and so future versions of Drupal could break it. Making a subrequest is using the API and so more maintainable.

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  • Why are you doing a subrequest and not using the Guzzle HTTP client to do your request?
    – Jaypan
    Jun 7, 2021 at 15:53
  • Someone suggested I use a Symfony subrequest in Slack. Won't a Guzzle HTTP client mean an actual separate request to the server? There are LOTS of paragraph entities involved, so adding actual HTTP requests would presumably be bad for performance.
    – joachim
    Jun 7, 2021 at 15:59
  • Updated question to explain more clearly that I want to put the JSON data from one inside the other.
    – joachim
    Jun 7, 2021 at 16:00

2 Answers 2

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After running the subrequest the request stack is quite a mess, it still contains the subrequest while the route match stack was cleaned up. If you then get the current route match this will return a newly created route match based on the json api request.

A quick fix would be to clean up the request stack by hand, including a check so that the code still works when the core issue is fixed:

$current_request = \Drupal::request();

$request = Request::create('/jsonapi/node/page/UUID', 'GET', [], $current_request->cookies->all(), [], $current_request->server->all());
$request->setSession($current_request->getSession());


$response = $kernel->handle($request, HttpKernelInterface::SUB_REQUEST);
if (\Drupal::request()->getPathInfo() !== $current_request->getPathInfo()) {
  \Drupal::requestStack()->pop();
}

BTW your subrequest probably needs more metadata from the main request. I've added cookies and server headers to the code example.

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  • That was exactly it -- the subrequest's route match was polluting things. Is that a core bug, and is there an issue for it? I've got it all working now, thank you!! :)
    – joachim
    Jun 9, 2021 at 9:52
  • Couldn't find an existing issue, filed drupal.org/project/drupal/issues/3218022.
    – joachim
    Jun 9, 2021 at 10:08
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I've since discovered that jsonapi_extras module provides the exact same functionality -- getting the JSONAPI representation of an entity by making a subrequest. That seems to avoid the problem by using the http_kernel.basic service to mak the subrequest. It looks like that doesn't keep a request stack, so bypasses the problem of multiple requests being kept track of?

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