Windows: no supported way to reopen console input (`CONIN$`) as a raw `tty.ReadStream` when stdin is a pipe

[edemaine]

Version

v24.11.0

Platform

Microsoft Windows NT 10.0.26200.0 x64

Subsystem

node:tty or node:fs

What steps will reproduce the bug?

Run the following code in a CommonJS setting (or convert requires to imports):

const fs = require("node:fs");
const tty = require("node:tty");
const fd = fs.openSync("\\\\.\\CONIN$", "r");
const input = new tty.ReadStream(fd);
input.setRawMode(true);

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

Windows

What is the expected behavior? Why is that the expected behavior?

Successful open of console/TTY in raw mode

What do you see instead?

\\.\CONIN$ opens and new tty.ReadStream(fd) reports isTTY: true, but setRawMode(true) throws EPERM.

Additional information

Motivation

A terminal TUI/pager such as hunk needs to read application data from stdin, while still interacting via keyboard/mouse input from the controlling console. For example:

git diff | hunk pager -

In this process, fd 0 is the pipe containing the diff, not the keyboard. On Unix, this can be handled by opening /dev/tty and passing that fd to new tty.ReadStream(fd), then calling setRawMode(true). On Windows, I expected \\.\CONIN$ to be the equivalent, and Node can open it and reports the resulting tty.ReadStream as a TTY, but setRawMode(true) fails with EPERM.

I also tried a few other names for CONIN$:

const fs = require("node:fs");
const tty = require("node:tty");

for (const path of ["CON", "CONIN$", "\\\\.\\CONIN$", "//./CONIN$"]) {
  try {
    const fd = fs.openSync(path, "r");
    const stream = new tty.ReadStream(fd);

    let result;
    try {
      stream.setRawMode(true);
      result = "raw ok";
      stream.setRawMode(false);
    } catch (error) {
      result = `raw failed: ${error.code} ${error.message}`;
    }

    console.error(path, {
      fd,
      isTTY: stream.isTTY,
      result,
    });

    stream.destroy();
  } catch (error) {
    console.error(path, "open failed:", error.code, error.message);
  }
}

Output:

CON open failed: ENOENT ENOENT: no such file or directory, open '...\CON'
CONIN$ open failed: ENOENT ENOENT: no such file or directory, open '...\CONIN$'
\\.\CONIN$ { fd: 3, isTTY: true, result: 'raw failed: EPERM setRawMode EPERM' }
//./CONIN$ { fd: 3, isTTY: true, result: 'raw failed: EPERM setRawMode EPERM' }

There should be a supported way for a Windows CLI/TUI application to reopen the controlling console input while stdin is a pipe, then enable raw mode on that input stream. Otherwise, tools that consume piped stdin but need interactive terminal input cannot work as full-screen TUIs on Windows without native addons or platform-specific external helpers.