XMLHttpRequest.getAllResponseHeaders should return lowercase header fields in sorted order

[ascherkus]

Description

The getAllResponseHeaders() specification indicates that "Let initialHeaders be the result of running sort and combine with this’s response’s header list", where a sort and combine is defined in the Fetch specification as "the result of convert header names to a sorted-lowercase set with all the names of the headers in list."

Basically we should expect to see "content-type" not "Content-Type" similar to what you'd see when running on a web browser.

React Native version:

System:
OS: Linux 5.4 Ubuntu 20.04.3 LTS (Focal Fossa)
CPU: (8) x64 Intel(R) Core(TM) i7-3770K CPU @ 3.50GHz
Memory: 3.14 GB / 31.31 GB
Shell: 5.0.17 - /bin/bash
Binaries:
Node: 16.10.0 - /tmp/yarn--1633648470824-0.633831050292539/node
Yarn: 1.19.1 - /tmp/yarn--1633648470824-0.633831050292539/yarn
npm: 7.24.0 - /usr/bin/npm
Watchman: Not Found
SDKs:
Android SDK:
API Levels: 29, 30, 31
Build Tools: 29.0.3, 30.0.2, 31.0.0
System Images: android-29 | Intel x86 Atom_64, android-29 | Google Play Intel x86 Atom
Android NDK: Not Found
IDEs:
Android Studio: Not Found
Languages:
Java: 11.0.11 - /usr/bin/javac
npmPackages:
@react-native-community/cli: Not Found
react: 17.0.2 => 17.0.2
react-native: 0.66.0 => 0.66.0
npmGlobalPackages:
react-native: Not Found
Done in 2.82s.

Steps To Reproduce

Provide a detailed list of steps that reproduce the issue.

1. Start up a HTTP/1 webserver that returns uppercased headers (e.g., Content-Type versus content-type -- HTTP/2 requires headers to be lowercased)
2. Request something via XMLHttpRequest and call getAllResponseHeaders():

let xhr = new XMLHttpRequest();
xhr.addEventListener('readystatechange', function (e) {
  if (xhr.readyState == 4) {
    console.log(xhr.getAllResponseHeaders());
  }
});

// Replace with your test server -- I couldn't easily find a public facing one
// since most appear to run through proxies that don't exhibit the desired behaviour.
xhr.open('GET', 'https://uppercase-headers-http1.com/');
xhr.send();

Expected Results

A sorted list of the headers with the field names lowercased. For example:

[
"content-type: application/json",
"transfer-encoding: chunked"
]

Instead the headers fields are retured verbatim:

[
"Content-Type: application/json",
"Transfer-Encoding: chunked"
]

I think the fix in https://github.com/facebook/react-native/blob/main/Libraries/Network/XMLHttpRequest.js#L421 isn't too bad -- perhaps we should be using this._lowerCaseResponseHeaders and sort the result instead of this.responseHeaders?

[stale]

Hey there, it looks like there has been no activity on this issue recently. Has the issue been fixed, or does it still require the community's attention? This issue may be closed if no further activity occurs. You may also label this issue as a "Discussion" or add it to the "Backlog" and I will leave it open. Thank you for your contributions.

[github-actions]

This issue was closed because it has been stalled for 7 days with no activity.