How to implement macro with async function inside?

[stereobooster]

• babel-plugin-macros version: 2.1.0
• node version: 8.6
• npm (or yarn) version: yarn 1.5.1

Relevant code or config

What you did:

What happened:

Reproduction repository:

https://github.com/stereobooster/lqip.macro

Problem description:

I want to implement lqip.macro. I'm not sure how to use async lqip in babel-plugin-macros, which seems to be expecting synchronous code. Am I wrong here? What is the way to work with async functions? Thanks

Suggested solution:

[kentcdodds]

Yes, this is a sad limitation to babel transforms. They are completely synchronous. @threepointone told me this crazy idea to make async node code run synchronously. It's going to be slow, but it works like a charm. Here's an example from real code that I'm using at PayPal:

const results = crossSpawn.sync('node', [
  '-e',
  `require("${spundlePath}")("${localesDir}", "${country}", "${locale}", (err, out) => {console.log(JSON.stringify(out))})`,
])
const en = JSON.parse(results.stdout)['en-US']

That should give you an idea of how to make it run synchronously. There may be a module for this.

In any case, I think we should either create a utility and expose that from babel-plugin-macros, or (probably better) create a module that makes this easier. What do you think?

[stereobooster]

Can we make babel to accept async function? I'm not aware of implementation details. I will try your code meantime.

[kentcdodds]

Unfortunately not. But @hzoo may have some other ideas.

[stereobooster]

I did this:

function syncLqip(path) {
  return execSync("node src/lqip.js " + path, { shell: false })
    .toString("utf8")
    .trim();
}

[stereobooster]

I found workaround for my case. Should we close this ticket or keep open to find general solution?

[kentcdodds]

Maybe we could add a link to this issue in the author.md docs file?

[Zemnmez]

I've made @kentcdodds solution into a more generic & cleaner micro library: https://github.com/Zemnmez/do-sync

[kentcdodds]

Very cool @Zemnmez! Thank you 💯