Async import from both worker and child worker: 'Cannot find module'

[mischnic]

🐛 bug report

Doing async imports in nested workers doesn't work beacuse ./loaders/worker/js-loader isn't available in the inner worker.

😯 Current Behavior

child-worker.b4a550ff.js:59 Uncaught Error: Cannot find module '2TfhN'
    at newRequire (child-worker.b4a550ff.js:59)
    at newRequire (child-worker.b4a550ff.js:43)
    at localRequire (child-worker.b4a550ff.js:81)
    at Object.1xm4F../loaders/worker/js-loader (child-worker.b4a550ff.js:144)
    at newRequire (child-worker.b4a550ff.js:69)
    at localRequire (child-worker.b4a550ff.js:81)
    at Object.39YhH../async.js (child-worker.b4a550ff.js:142)
    at newRequire (child-worker.b4a550ff.js:69)
    at child-worker.b4a550ff.js:118
    at child-worker.b4a550ff.js:141

💁 Possible Solution

This is probably because the context is actually the same between main and child worker, so Parcel thinks it can reuse the asset from a parent bundle?

💻 Code Sample

parcel build index.html --no-scope-hoist

<script src="index.js"></script>

// index.js
new Worker("./worker.js");

// worker.js
new Worker("./child-worker.js");
import("./async.js").then((v) => console.log("worker: async=", v));

// child-worker.js
import("./async.js").then((v) => console.log("child worker: async=", v));

// async.js
export const async = "async!";

🌍 Your Environment

Software	Version(s)
Parcel	f89e5ef

[mischnic]

Another case that might be caused by the same problem:

Uncaught Error: Cannot find module 'WkjLV'
    at newRequire (ParcelWorker.3cce57a2.js:59)
    at newRequire (ParcelWorker.3cce57a2.js:43)
    at localRequire (ParcelWorker.3cce57a2.js:81)
    at Object.1iSde../bundle-manifest (ParcelWorker.3cce57a2.js:142)
    at newRequire (ParcelWorker.3cce57a2.js:69)
    at ParcelWorker.3cce57a2.js:118
    at ParcelWorker.3cce57a2.js:141
    at ParcelWorker.3848616d.js:1

parcel build index.html --no-scope-hoist

<script src="index.js"></script>

// index.js
new Worker("./ParcelWorker.js");

// ParcelWorker.js
import './Parcel';
import("./async.js").then((v) => console.log("worker: async=", v));

// async.js
console.log("async");
export const async = "async!";

// Parcel.js
import WorkerFarm from './Worker';

// Worker.js
import "./common.js";
if (Date.now() === 0) {
	new Worker("./child.js");
}

// common.js
(some large file to trigger this becoming a shared bundle: 20kb)

// child.js
import "./Parcel";

[lgarron]

I'm also able to trigger this with normal module imports:

https://github.com/lgarron/parcel-2-worker-common-import

The cubing package contains a lot of imports, but a search of cubing/dist/esm (which you can confirm is used by Parcel by deleting cubing/dist/cjs) shows that there are no async import calls.