RequestInit: duplex option is required when sending a body

[cyco130]

Version

v18.13.0

Platform

Linux xxx 5.15.0-58-generic #64~20.04.1-Ubuntu SMP Fri Jan 6 16:42:31 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

Subsystem

undici

What steps will reproduce the bug?

Run the following line of code (in REPL or a script)

new Request("http://example.com", { method: "POST", body: new ReadableStream() });

How often does it reproduce? Is there a required condition?

All the time.

What is the expected behavior?

No error thrown.

What do you see instead?

Uncaught TypeError: RequestInit: duplex option is required when sending a body.
    at new Request (node:internal/deps/undici/undici:7090:19)

Additional information

Behavior of other versions:

• v16.19.0 fails, v.16.18.1 works (with --experimental-fetch option and ReadableStream imported from stream/web)
• >= 19.1 fails, 19.0.1 works
• v18.12.1 and lower works

[KhafraDev]

The error is expected, see whatwg/fetch#1457

[cyco130]

So this happens because Node can't do full duplex when streaming so duplex: "half" has to be explicitly set, is that it?

Ugh, it's gonna break so many things :/

[climba03003]

So this happens because Node can't do full duplex when streaming so duplex: "half" has to be explicitly set, is that it?

I believe it is a changes from specification to force it to be a must. You may see the same in foreseeable future for other implementer of fetch if they follow specification.

[nedataghizadeh79]

maybe This error occurs because you are passing a ReadableStream as the body of the request without providing the duplex option in the RequestInit object.

To fix the error, you can provide the duplex option and set it to true, like this:

new Request("http://example.com", { method: "POST", body: new ReadableStream(), duplex: true });

This tells the Request constructor that the body is a duplex stream that can both be read from and written to.

Note that the duplex option is required when sending a ReadableStream as the body of the request, as stated in the error message.

[hillar]

The error is expected, see whatwg/fetch#1457

just do not forget duplex: 'half', for example piping one fetch to another

async function pipeUrlToUrlwithFetch(url1, url2) {
  const getResponse = await fetch(url1);
  const options = {
    method: 'POST',
    body: getResponse.body,
    duplex: 'half',
  };
  const postResponse = await fetch(url2, options);
  return postResponse.json();
}

pipeUrlToUrlwithFetch('https://jsonplaceholder.typicode.com/posts/1', 'https://jsonplaceholder.typicode.com/posts')
.then(result => {console.log(result);})
.catch(error => {console.error(error);});

[KevinBLT]

Why the spec did not just came up with applying the only sane default value to duplex: 'half' (and that is easy, because it's the only actual value at the moment) but instead forcing everybody to insert this options with only one available value is out of my mind.