bin-v8-flag-filter-sync/index.js

This package is inspired from the [bin-v8-flags-filter](https://www.npmjs.com/package/bin-v8-flags-filter) package in npm.

var spawn = require('child_process').spawnSync;

var FLAGS = [
    'debug',
    '--debug',
    '--debug-brk',
    '--inspect',
    '--inspect-brk',
    '--expose-gc',
    '--gc-global',
    '--es_staging',
    '--no-deprecation',
    '--prof',
    '--log-timer-events',
    '--throw-deprecation',
    '--trace-deprecation',
    '--use_strict',
    '--allow-natives-syntax',
    '--perf-basic-prof',
    '--experimental-repl-await'
];

var FLAG_PREFIXES = [
    '--harmony',
    '--trace',
    '--icu-data-dir',
    '--max-old-space-size',
    '--preserve-symlinks'
];

var DEFAULT_FORCED_KILL_DELAY = 30000;

function getChildArgs (cliPath, ignore) {
    var args = [cliPath];

    process.argv.slice(2).forEach(function (arg) {
        var flag = arg.split('=')[0];

        if (ignore.indexOf(flag) > -1) {
            args.push(arg);
            return;
        }

        if (FLAGS.indexOf(flag) > -1) {
            args.unshift(arg);
            return;
        }

        for (var i = 0; i < FLAG_PREFIXES.length; i++) {
            if (arg.indexOf(FLAG_PREFIXES[i]) === 0) {
                args.unshift(arg);
                return;
            }
        }

        args.push(arg);
    });

    return args;
}

function setupSignalHandler (signal, childProcess, useShutdownMessage, forcedKillDelay) {
    function forceKill () {
        childProcess.kill('SIGTERM');
    }

    function handler () {
        if (useShutdownMessage)
            childProcess.send('shutdown');
        else
            childProcess.kill(signal);

        setTimeout(forceKill, forcedKillDelay).unref();
    }

    process.on(signal, handler);
}

module.exports = function (cliPath, opts) {
    var useShutdownMessage = opts && opts.useShutdownMessage;
    var forcedKillDelay    = opts && opts.forcedKillDelay || DEFAULT_FORCED_KILL_DELAY;
    var ignore             = opts && opts.ignore || [];
    var args               = getChildArgs(cliPath, ignore);

    var cliProc = spawn(process.execPath, args, { stdio: [process.stdin, process.stdout, process.stderr] });


    setupSignalHandler('SIGINT', cliProc, useShutdownMessage, forcedKillDelay);
    setupSignalHandler('SIGBREAK', cliProc, useShutdownMessage, forcedKillDelay);

    if (useShutdownMessage) {
        process.on('message', function (message) {
            if (message === 'shutdown')
                cliProc.send('shutdown');
        });
    }
};