@effection/node

node.js

import child_process from 'child_process';

/**
 * Continue a process once an event is received:
 * ```ts
 * yield untilEvent(mocha, 'onTestStarted');
 *
 */ 
function untilEvent(emitter, eventName) {
  return execution => {
    let handle = (...args) => execution.resume(args);

    emitter.on(eventName, handle);

    return () => emitter.off(eventName, handle);
  };
}
/**
 * Spawn a process using command and arguments. It will raise if the child 
 * process has a non-zero exit status or is interrupted.
 * e.g. 
 * ```js
 * // spawn child process, and continue once it exits successfully.
 * yield spawn("/usr/bin/chrome", ['--no-data-dir', '--disable-popups']);
 * 
 * // spawn child process, but continue immediately.
 * this.fork(spawn("/usr/bin/chrome", ['--no-data-dir', '--disable-popups']));
 * ```
 */
function spawn(cmd, args) {
  return function*() {
    let process = child_process.spawn(cmd, args);

    // listen for errors
    let errors = this.fork(function*() {
      let [ error ] = yield untilEvent(process, 'error');
      throw error;
    });

    try {
      let [ code, signal ] = yield untilEvent(process, 'exit');

      if (code != null & code !== 0) {
        let error =  new Error(`'${cmd} ${args.join('')}' exited with non zero exit status`);
        error.name = 'NonZeroExitError';
        throw error;
      } else if (signal != null) {
        let error = new Error(`interrupted with ${signal}`);
        error.name = 'SignalError';
        throw error;
      }
    } finally {
      errors.halt();
      process.kill();
    }
  };
}