Attach .subprocess to the execa promise

[sindresorhus]

Node.js does this now for childProcess. when you promisify it.

https://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback

The name is to be decided.

One day, I hope we can get rid of execa() being both a childProcess and promise and just have the .child property on the promise. But that's a huge breaking change. For now, the best we can do is to add it, and recommend new users to use it instead of the old way. We could even un-document the old way.

@ehmicky Thoughts?

[ehmicky]

Yes this sounds good 👍

[sindresorhus]

Any thoughts on the name?

• .child
• .process
• .subprocess
• .childProcess

[ehmicky]

.child since this is the name used by Node.js util.promisify(childProcess.exec)?

[sindresorhus]

👍

[ehmicky]

@wesleytodd Based on your comment here, would you like to take a look at doing a PR for this feature? Please let us know if you need any help!

[wesleytodd]

I plan to, just have other priorities at work. If someone else gets to it before me that’s fine, my guess is I will be able to do it late next week at the earliest.

[ehmicky]

Per this comment, we are going to name the property subprocess instead.

[ehmicky]

We probably should keep the following specific methods on the returned promise, as opposed to the promise.subprocess property: .pipe() and [Symbol.asyncIterator]/.iterable(). That's because when those methods are called, the promise is awaited indirectly/differently. So those methods are more related to the promise than to the subprocess instance.

This leads a much more natural syntax.

const result = await execa`npm run build`
  .pipe`sort`
  .pipe`head -n 2`;

for await (const line of execa`npm run build`) {
  // ...
}

for await (const line of execa`npm run build`.iterable().drop(3)) {
  // ...
}

Instead of:

const result = await execa`npm run build`
  .subprocess.pipe`sort`
  .subprocess.pipe`head -n 2`;

for await (const line of execa`npm run build`.subprocess) {
  // ...
}

for await (const line of execa`npm run build`.subprocess.iterable().drop(3)) {
  // ...
}

All the other properties/methods though can be on the .subprocess property.