TypeError: process.stdout.cursorTo is not a function

[hyunbinseo]

Describe the bug

After upgrading to SvelteKit 1.17.0+ endpoint prerender with process.stdout.cursorTo() fails.

Seems to be related to https://github.com/sveltejs/kit/pull/9919 - prerender in worker rather than subprocess to support Deno.

Reproduction

// src/routes/+server.ts

import type { RequestHandler } from './$types';

export const prerender = true;

export const GET = (() => {
  const now = new Date().toISOString();
  process.stdout.write(now);
  process.stdout.cursorTo(0);
  return new Response(now);
}) satisfies RequestHandler;

npm i @sveltejs/[email protected]
npm run build

✓ built in 217ms

TypeError: process.stdout.cursorTo is not a function

node:internal/event_target:1012
 process.nextTick(() => { throw err; });
                          ^
Error: 500 /

Logs

No response

System Info

System:
  OS: macOS 13.3.1
  CPU: (10) arm64 Apple M1 Pro
  Memory: 158.95 MB / 16.00 GB
  Shell: 5.9 - /bin/zsh
Binaries:
  Node: 18.16.0 - ~/.nvm/versions/node/v18.16.0/bin/node
  npm: 9.5.1 - ~/.nvm/versions/node/v18.16.0/bin/npm
Browsers:
  Chrome: 113.0.5672.126
  Firefox: 113.0.1
  Safari: 16.4
npmPackages:
  @sveltejs/adapter-auto: ^2.0.0 => 2.1.0 
  @sveltejs/kit: ^1.17.0 => 1.17.0 
  svelte: ^3.54.0 => 3.59.1 
  vite: ^4.3.0 => 4.3.8

Severity

blocking an upgrade

Additional Information

No response

[gtm-nayan]

Related https://github.com/nodejs/node/issues/28386

[hyunbinseo]

Solution

Check if a stream is connected to a TTY context.

const { isTTY } = process.stdout;
if (isTTY) process.stdout.write('-'.repeat(100));

Reference

process.stdout.fd

This property refers to the value of underlying file descriptor of process.stdout. The value is fixed at 1. In Worker threads, this field does not exist.

---

A note on process I/O

$ node -p "Boolean(process.stdin.isTTY)"
# true

$ echo "foo" | node -p "Boolean(process.stdin.isTTY)"
# false

$ node -p "Boolean(process.stdout.isTTY)"
# true

$ node -p "Boolean(process.stdout.isTTY)" | cat
# false