Using Node'18 --watch mode with esm and swc

[jraoult]

I realise I'm going very niche here. Still, I think the new Node's --watch mode is a fantastic opportunity for ts-node to get a watch mode for "free" without the complexity of getting another library involved. You can read about this experimental feature in the official doc if you are not familiar with it.

I tried to get it to work with NODE-OPTIONS='--watch' ts-node --esm --swc (my combo of choice these days), but it gets into an infinite restart loop. I know the --esm mode works with 2 processes, so I suspect the first process is dynamically updating a dependency detected by --watch which ten restarts the whole thing. I tried to debug it but couldn't find a satisfying answer so may be my hypothesis is wrong.

I ended up hacking my loader like so:

import { createEsmHooks, register } from "ts-node";

export const { resolve, load, getFormat, transformSource } = createEsmHooks(
  register({ transpileOnly: true, swc: true, esm: true })
);

and I use it with node --loader myloader.mjs --watch myEntry.ts

It works perfectly so for but having it working out of the box in ts-node would be a better DX.

@cspotcode any idea why it would restart like that? If you guide me, I'm happy to help with a PR.

[SrBrahma]

Up. Having to install ts-node-dev is a thing from the past decade!

[jraoult]

@cspotcode I'm still happy to create a PR for this if you think it makes sense 😀 I've been using it for months now, and it works well.

[Khaaz]

Awesome! Would be nice to have it built in indeed!

[Khaaz]

@jraoult Hi, I don't know if that helps but I also have regularly the infinite restart loop when using node --watch on native js with no other tools.
Usually I just starts it once without watch mode and then it works again in watch mode.