Supports WebWorker using comlink

[yukukotani]

A proposal to support WebWorker using comlink. This is inspired by singleton mode of comlink-loader.

Maybe we can implement this as a plugin, but i don't know how to generate proxy.js in plugin. It seems that load function can returns only one file for each extensions, so I think generating both *.worker.js and *.worker.proxy.js is impossible in current plugin architecture.

Example

Source

calc.worker.js

export async function calcInWorker(str) {
  // something heavy
  return `calculated: ${str}`;
}

main.js

import { calcInWorker } from "./calc.worker.js";

const result = await calcInWorker("example");
console.log(result);

Dist

calc.worker.js

import { expose } from "comlink";

async function calcInWorker(str) {
  // something heavy
  return `calculated: ${str}`;
}

expose({ calcInWorker });

calc.worker.proxy.js

import { wrap } from "comlink";

const worker = new Worker("calc.worker.js", { type: "module" });
const wrappedWorker = wrap(worker);

export async function calcInWorker(str) {
  return await wrappedWorker.calcInWorker(str);
}

main.js

import { calcInWorker } from "./calc.worker.proxy.js";

const result = await calcInWorker("example");
console.log(result);

[yukukotani]

@FredKSchott I'd like to ask your opinion!

I think this proposal is not web standard and shouldn't be included in snowpack core. To realize this proposal as a plugin, we need to extend current plugin architecture to generate .proxy.js. What do you think??

[yukukotani]

I've just found #1122. This seems to be a good solution!