Gulp + TSC hack

gulpfile.js

let isWatching = false;

gulp.task('ts', () => {
    return new Promise((resolve, reject) => {
        const cmd = 'npx';
        const args = ['tsc'];

        if (isWatching) {
            args.push('-w', '--preserveWatchOutput');
        }

        const tsc = spawn(cmd, args);
        const sanitizeTSCOutput = (data) => data.toString().trim();

        tsc.stdout.on('data', (data) => {
            const message = sanitizeTSCOutput(data);
            log(message);

            // Hack to let gulp know we have the watcher online
            if (isWatching && message.includes('Watching for file changes')) {
                resolve();
            }
        });

        tsc.stderr.on('data', (data) => {
            log(sanitizeTSCOutput(data));
        });

        tsc.on('error', log);

        tsc.on('close', (code) => {
            if (!isWatching) {
                code !== 0 ? reject('TSC failed') : resolve();
            }
        });
    });
});

gulp.task('watch', gulp.series(function setIsWatching(cb) {
    isWatching = true;
    cb();
}, 'ts'));

ping