Ideas? about execa

[sindresorhus]

@revelt Either execa(commandApp, commandAttributes, {stdio: 'inherit'}) or use the --color flag to force colors.

[callumlocke]

I often want stdio: 'inherit' behaviour (which is normally only an option with cp.spawn() or execa.spawn(), I think) but with the simple promise-returning API of execa().

The stdio: 'inherit' option lets you watch logs coming from the child process live and incrementally (and in colour!), which is what I want 50% of the time. But it means I have to use spawn, and therefore have to manually hook up event listeners to handle the child process ending or erroring.

I often find myself writing a wrapper like this:

function run(file, args, options = {}) {
  return new Promise((resolve, reject) => {
    const child = execa.spawn.call(
      null, file, args, Object.assign({ stdio: 'inherit' }, options)
    );

    child.on('error', reject);
    child.on('exit', code => {
      if (code === 0) resolve();
      else reject();
    });
  });
}

It would be great if execa() could introduce an option like this.

Even better would be if there was some nice way to visually distinguish the child logs as being from the child process, like prefixing each line with > or something (but still retaining ANSI colour codes in the child logs).

---

EDIT

Just thought of another way of approaching this, maybe the solution is simply to add a new promise-returning method to spawned child process objects:

const child = execa.spawn(...);
const {stdio, stderr} = await child.exited();

I guess this would give the most flexibility, as you still get access to a ChildProcess instance (in case you need to send a signal to it, or something) but you also get the convenience of a promise-based way to monitor its completion.

Maybe the .exited() method (not sure about the name) could even take an argument to set the expected exit code, e.g. .exited(0) would mean any non-zero exit code causes a rejection.

[sindresorhus]

@callumlocke I really like the idea! I've had similar needs. Would you mind moving this into a new issue?

[zealoushacker]

IPC support, like in child_process.spawn's options.stdio would be awesome.

child-process-promise seems to do a good job of this, because it's a wrapper and supports the same options as the thing it's trying to improve, is that why you had chosen not to go that route?

[sindresorhus]

@zealoushacker Should already be supported, since we use child_process.spawn() internally, but needs to be tested and documented.

[tpetry]

Automatic handling of timeout by execa for executed processes would be nice. You define a max running time of e.g. 15000ms and the executed process has to finish within this time limit or will be killed. This is very useful for any application which has to fulfill QoS criterias.

[sindresorhus]

@tpetry execa already has a timeout option:

execa(file, [arguments], [options])

Same options as child_process.execFile.

[tpetry]

My fault, you're right. Didn't look up the options because i expected the same options as child_process.spawn

[revelt]

Is there a way to make it so that the output of the commands run via execa is coloured in the terminal?

I'm running it this way:

execa(commandApp, commandAttributes).stdout.pipe(process.stdout)

but everything in the terminal (tested on both hyper.js and iTerm) is black and white.

To give some context, I'm using execa in fol to allow people to input a folder name, then let them pick a subfolder from a list, then place that choice into user's chosen terminal command. I need this, for example, to call gulp with a flag and a name of a subfolder, like gulp -t vip_template_64. That subfolder name varies, it's the different template I pick each time.

I got it wired and working, just the stdout output is uncoloured.

Thanks in advance.

[revelt]

@sindresorhus it worked! thanks a lot.