[node-core-library] SubprocessTerminator ignores SIGHUP, so detached children outlive a closed terminal #6124

🤖 Filed by GitHub Copilot acting for Naman Kanakiya (@namankanakiya) (light review only).

Package: @rushstack/node-core-library 5.25.1. Linux/macOS (non-Windows).

Repro: script.js:

const { SubprocessTerminator } = require('@rushstack/node-core-library');
const c = require('child_process').spawn('sleep', ['1000'], SubprocessTerminator.RECOMMENDED_OPTIONS);
SubprocessTerminator.killProcessTreeOnExit(c, SubprocessTerminator.RECOMMENDED_OPTIONS);
setInterval(() => {}, 1000);

Run it in a terminal, then close the terminal (or kill -HUP <pid>).

Observed: sleep keeps running with ppid 1. RECOMMENDED_OPTIONS (detached: true) puts the child in its own session, so the terminal's hangup never reaches it, and killProcessTreeOnExit only handles SIGINT, SIGTERM and exit. With SIGINT or SIGTERM the child is killed as expected.

Expected: on non-Windows, SIGHUP is handled like SIGINT/SIGTERM, so closing the terminal of a tool that uses SubprocessTerminator does not leak its detached children.

Suggested fix: in _ensureInitialized, also process.prependListener('SIGHUP', _onTerminateSignal), and remove it in _cleanupChildProcesses.

Happy to test a candidate fix.