ZenFS Streams

A modern polyfill for node:stream.

This package replaces readable-stream in ZenFS. readable-stream made up 10 of the 17 dependencies in the @zenfs/core tree and totaled 703 KB unpacked, and it has a number of unresolved problems with its types and legacy code.

It is written in TypeScript against Node's current implementation, and every exported class is declared implements its node:stream counterpart.

Usage

import { Readable, Writable, pipeline } from '@zenfs/streams';

await pipeline(
	Readable.from(['hello', ' ', 'world']),
	new Writable({
		write(chunk, encoding, callback) {
			console.log(chunk.toString());
			callback();
		},
	})
);

Notes

• The only runtime dependency is buffer, which resolves to the built-in module on Node. events, process, abort-controller and string_decoder are not needed: EventEmitter and StringDecoder are implemented here, and AbortController and queueMicrotask are used directly.
• StringDecoder decodes UTF-8 with a streaming TextDecoder. UTF-16LE is handled separately, since Node drops a trailing odd byte and preserves lone surrogates where the WHATWG decoder replaces both with U+FFFD.
• Outside Node there is no process.nextTick, so callbacks fall back to queueMicrotask. Node drains its next-tick queue ahead of the microtask queue; the fallback has no equivalent, so those callbacks interleave with promise continuations rather than preceding them.
• finished() on a WHATWG stream needs the closed-promise symbol that node:stream (and this package's toWeb()) attaches. A plain ReadableStream cannot be observed without consuming it, so it is rejected.
• setMaxListeners is honored as state but never produces Node's MaxListenersExceededWarning.