Start: createServerFn cannot return raw response objects

[nekochan0122]

Which project does this relate to?

Start

Describe the bug

Server functions should able to return Raw Response objects.

Your Example Website or App

https://github.com/nekochan0122/tanstack-start-return-response-object

Steps to Reproduce the Bug or Issue

1. Open the dev server
2. Click the "Trigger serverFn" button
3. See the console output and cookies

Expected behavior

const serverFn = createServerFn({ method: "POST" }).handler(async () => {
  return new Response(JSON.stringify({ hello: "world" }), {
    status: 200,
    headers: {
      "Content-Type": "application/json",
      "Set-Cookie": "test=test",
    },
  });
});

1. The console output is expected to contain { hello: "world" }
2. The cookie should be set to test=test

Screenshots or Videos

No response

Platform

• OS: [e.g. macOS, Windows, Linux]
• Browser: [e.g. Chrome, Safari, Firefox]
• Version: [e.g. 91.1]

Additional context

No response

[nekochan0122]

a temporary solution:

async function handleResponse<ResponseBody = unknown>(response: Response): Promise<ResponseBody> {
  const event = getEvent()

  setHeaders(event, Object.fromEntries(response.headers))

  switch (response.headers.get('Content-Type')) {
    case 'application/json':
      return response.json() as ResponseBody

    default:
      return response.body as ResponseBody
  }
}

[cpakken]

Tried https://discord.com/channels/719702312431386674/1310732156561260575/1310785299915346100

const exampleStreamingFn = createServerFn({ method: 'GET' }).handler(async () => {
  const encoder = new TextEncoder();

  // replace with ur actual stream
  const stream = new ReadableStream({
    async start(controller) {
      for (let i = 0; i < 10; i++) {
        const chunk = encoder.encode(`${i + 1}`);
        controller.enqueue(chunk);
        await new Promise((resolve) => setTimeout(resolve, 100));
      }
      controller.close();
    },
  });

  const res = new Response(stream, { status: 200 });

  return sendWebResponse(getEvent(), res);
});

and https://discord.com/channels/719702312431386674/1310732156561260575/1310785660948578355

const res = await fetch(exampleStreamingFn.url);

Which got streaming kindof working, but after stream is done im getting.

ServerFn Response: 200
 - Payload: {"result":{"$undefined":""},"context":{}}

node:_http_outgoing:699
    throw new ERR_HTTP_HEADERS_SENT('set');
          ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
    at ServerResponse.setHeader (node:_http_outgoing:699:11)  

and then vinxi crashes and I need to restart the server