Trying to set a header for an error response

[atomic spruce]

When trying to implement RFC9457 using Nuxt, I am having a problem sending the content-type "application/problem+json" to an error response using sendError, as shown in the example below:

if (allQueries.length > 0 && !hasValidQueries) {
        setResponseHeaders(event, {
            'Content-Type': 'application/problem+json',
        });

        // event.headers.set('Content-Type', 'application/problem+json');

        // event.node.res.setHeader('Content-Type', 'application/problem+json');

        return sendError(event, createError({
            statusCode: 400,
            statusMessage: 'Invalid query',
            stack: event.context.clientAddress,
            data: {
                type: 'about:blank',
                title: 'Bad Request',
                status: 400,
                detail: 'You can only use group_id or group_name as query.',
                instance: event.path,
            }
        }))
}

None of the ways tried define the desired header, but if I comment out sendError and return a common message, like the example below, the header is defined.

if (allQueries.length > 0 && !hasValidQueries) {
        setResponseHeaders(event, {
            'Content-Type': 'application/problem+json',
        });

        return {
            test: 'Send Erro'
        }
}

Any idea what I should do to set a header using sendError?

[unique nexus]

You could try throwing sendError instead of returning it?

Or use creatError and the docs say you should throw that
https://nuxt.com/docs/getting-started/error-handling#createerror

It looks like sendError is a h3 internal function that probably shouldn't be used. And on this line it overwrites the content header https://github.com/unjs/h3/blob/c04c458810e34eb15c1647e1369e7d7ef19f567d/src/error.ts#L170

Docs say to throw createError https://h3.unjs.io/guide/event-handler#responses-types

[atomic spruce]

Firstly thanks for the help!

When I use sendError it is to obtain a JSON response in the request, because when using createError by launching directly I do not obtain a JSON response.

But I understand that the h3 documents do not have sendError documented, so there is no way to do this in Nuxt? To return an expected response in case of an error?

Or in this case should I use another means than createError? If you know what the option would be to obtain a JSON response I would greatly appreciate it.

[unique nexus]

when using createError by launching directly I do not obtain a JSON response
oh really? It should return json, are you using an API client like postman or are you using the browser?

So looking at the code I think if you throw creatError it will call sendError anyway and that overrides the content-type to be json.

So you could try making your own custom sendError that doesn't do this

export function customSendError(
  event: H3Event,
  error: Error | H3Error,
  debug?: boolean,
) {
  if (event.handled) {
    return;
  }

  const h3Error = isError(error) ? error : createError(error);

  const responseBody = {
    statusCode: h3Error.statusCode,
    statusMessage: h3Error.statusMessage,
    stack: [] as string[],
    data: h3Error.data,
  };

  if (debug) {
    responseBody.stack = (h3Error.stack || "").split("\n").map((l) => l.trim());
  }

  if (event.handled) {
    return;
  }
  const _code = Number.parseInt(h3Error.statusCode as unknown as string);
  setResponseStatus(event, _code, h3Error.statusMessage);
  // event.node.res.setHeader("content-type", MIMES.json);
  event.node.res.setHeader("content-type", "application/problem+json");
  event.node.res.end(JSON.stringify(responseBody, undefined, 2));
}

I hope this works for you. Just a little annoying that h3 overwrites your custom content-type header
Might even be good to open an issue or PR on this