Node 22.3.0 regression: undici sends invalid origin header in some cases

[mickdermack]

Bug Description

Since v6.16.1, undici sends the origin header as origin: https://origin.example.com, undefined in some cases.

This reproducibly happens when sending a POST request, with the origin header explicitly specified in headers and redirect: "error".

Reproducible By

import { fetch } from 'undici';

async function repro() {
  let api_url = "http://localhost:8080";
  let response = await fetch(api_url, {
    "headers": {        
      "origin": "https://origin.example.com"            
    },
    "body": "",    
    "method": "POST",
    "redirect": "error"
  });
}

await repro();

Expected Behavior

I expected the origin header to be sent as origin: https://origin.example.com.

Logs & Screenshots

complete request sent with undici v6.16.1 and above:

POST / HTTP/1.1
host: localhost:8080
connection: keep-alive
origin: https://origin.example.com, undefined
content-type: text/plain;charset=UTF-8
accept: */*
accept-language: *
sec-fetch-mode: cors
user-agent: undici
accept-encoding: gzip, deflate
content-length: 0

complete request sent with undici v6.16.0:

POST / HTTP/1.1
host: localhost:8080
connection: keep-alive
origin: https://origin.example.com
content-type: text/plain;charset=UTF-8
accept: */*
accept-language: *
sec-fetch-mode: cors
user-agent: undici
accept-encoding: gzip, deflate
content-length: 0

Environment

Arch Linux, Node.js v22.3.0

Additional context

[ronag]

@KhafraDev

[KhafraDev]

Caused by 0a66d30, will fix soon