[Bug?]: Middleware with returned undici response ignores the content-type if the response body is async.

[dominikzogg]

Duplicates

• [X] I have searched the existing issues

Latest version

• [X] I have tested the latest version

Current behavior 😯

I get Content-Type: text/html if i return a response in a middleware with a async body.

import { Response } from 'undici';

return new Response(bodyStream.iterator(), {
      status: 200,
      statusText: 'OK',
      headers: {'content-type': 'application/json'},
    });

If the bodyStream is not async it does work.

import { Response } from 'undici';

const streamToBuffer = async (stream: Stream): Promise<Buffer> => {
  return new Promise<Buffer>((resolve, reject) => {
    const list: Array<Uint8Array> = [];

    stream.on('data', (chunk) => list.push(chunk));
    stream.on('end', () => resolve(Buffer.concat(list)));
    stream.on('error', (error) => reject(error));
  });
};

return new Response(await streamToBuffer(bodyStream), {
      status: 200,
      statusText: 'OK',
      headers: {'content-type': 'application/json'},
    });

Expected behavior 🤔

I expect that the content-type passed as a headers is maintained in async and sync bodies on response.

Steps to reproduce 🕹

Steps:

1. Create a Middleware
2. Return a Response (undici) with a async bodyInit and a headersInit with a content-type for example 'application/json'
3. Do a request which hits the middleware and check the content-type on the response.

Context 🔦

No response

Your environment 🌎

System:
  OS: Fedora 39
  CPU: x86_64
Binaries:
  Node: 20.11.1 (/run/user/1000/fnm_multishells/128003_1711479810299/bin/node)
  pnpm: 8.15.4 (/run/user/1000/fnm_multishells/128003_1711479810299/bin/pnpm)
npmPackages:
 all of solid start +
 "undici": "^6.10.2"
 "undici-types": "^6.10.1"

[dominikzogg]

This is the bridging code https://github.com/chubbyts/chubbyts-http-undici-bridge

[ryansolid]

Hmm.. do you know if this is specific to undici? With Nitro I believe stuff like Response gets patched globally. I'm just wondering if this is an issue with how we are handling Responses from middleware in general or if this is due to some weirdness in the adapter layer.

[dominikzogg]

@ryansolid what i can tell is, that the content-type header is part of the response object, but not part of the headers I get when calling it via curl.

[ryansolid]

Moved this to Vinxi since it is lower level than we'd probably look at: https://github.com/nksaraf/vinxi/issues/292