Allow multiple readers at once

[ehmicky]

When get-stream is used, other readers cannot be used at the same time.

For example, this does not work (both calls will compete for the same data):

await Promise.all([
  getStream(stream),
  getStream(stream),
])

This creates some limitations for users. For example, in Execa, the following does not work:

import {execa} from 'execa'

const subprocess = execa(...)
subprocess.stdout.on('data', chunk => {...})
const {stdout} = await subprocess

Because the data event and the stdout buffering compete for the same data. Users have to opt-out of stdout buffering by using the buffer: false option.

However, it does not have the be this way. The issue here is that get-stream uses Readable[Symbol.asyncIterator]. The default implementation relies on calling stream.read() repeatedly. This works but does not allow for multiple readers at once.

Instead, using stream.on('data') would allow for multiple readers at once. We should make get-stream use that instead.

Since get-stream supports not only Node.js Readable streams but any async iterable, this logic would only be used when a Node.js Readable stream is passed.

[sindresorhus]

👍

[sindresorhus]

uses Readable[Symbol.asyncIterator]. The default implementation relies on calling stream.read() repeatedly. This works but does not allow for multiple readers at once.

Worth opening a Node.js issue about this?

[ehmicky]

nodejs/node#52086