sync-child-process

This package exposes a SyncChildProcess class that allows Node.js to run a
subprocess synchronously and interactively.

[API Docs]

[API Docs]: https://sass.github.io/sync-child-process/classes/SyncChildProcess.html

Usage

Use [new SyncChildProcess()] to start running a subprocess. This supports the
same API as [child_process.spawn()] other than a few options. You can send
input to the process using [process.stdin], and receive events from it
(stdout, stderr, or exit) using [process.next()]. This implements [the
iterator protocol], but not the iterable protocol because it's intrinsically
stateful.

[new SyncChildProcess()]: https://sass.github.io/sync-child-process/classes/SyncChildProcess.html#constructor
[child_process.spawn()]: https://nodejs.org/api/child_process.html#child_processspawncommand-args-options
[process.stdin]: https://sass.github.io/sync-child-process/classes/SyncChildProcess.html#stdin
[process.next()]: https://sass.github.io/sync-child-process/classes/SyncChildProcess.html#next
[the iterator protocol]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#the_iterator_protocol

``js
import {SyncChildProcess} from 'sync-child-process';
// or
// const {SyncChildProcess} = require('sync-child-process');

const node = new SyncChildProcess('node', ['--interactive']);

for (;;) {
if (node.next().value.data.toString().endsWith('> ')) break;
}

node.stdin.write("41 * Math.pow(2, 5)\n");
console.log((node.next().value.data.toString().split("\n")[0]));
node.stdin.write(".exit\n");
console.log(Node exited with exit code ${node.next().value.code});
`

Why synchrony?

See [the sync-message-port documentation] for an explanation of why running
code synchronously can be valuable even in an asynchronous ecosystem like
Node.js

[the sync-message-port documentation]: https://github.com/sass/sync-message-port?tab=readme-ov-file#why-synchrony

$3

Although Node's built-in [child_process.spawnSync()] function does run
synchronously, it's not interactive. It only returns once the process has run to
completion and exited, which means it's not suitable for any long-lived
subprocess that interleaves sending and receiving data, such as when using the
[embedded Sass protocol].

[child_process.spawnSync()`]: https://nodejs.org/api/child_process.html#child_processspawnsynccommand-args-options
[embedded Sass protocol]: https://github.com/sass/sass/blob/main/spec/embedded-protocol.md

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Disclaimer: this is not an official Google product.