[Bug]: `Worker` class of `jest-worker` does not support ESM worker modules

Version

v27.4.7

Steps to reproduce

An exception is raised, if I try to initialise a worker with an ESM module: new Worker('path/to/ESMworker.mjs'). Looks like jest-worker is simply trying to require the module and that does not work: https://github.com/facebook/jest/blob/d1bc333c549ffb53691e1ba68b16a21915fc5fdc/packages/jest-worker/src/workers/processChild.ts#L113-L114

https://github.com/facebook/jest/blob/d1bc333c549ffb53691e1ba68b16a21915fc5fdc/packages/jest-worker/src/workers/processChild.ts#L96-L97

https://github.com/facebook/jest/blob/d1bc333c549ffb53691e1ba68b16a21915fc5fdc/packages/jest-worker/src/index.ts#L32-L33

I was trying to refactor the code using the requireOrImportModule from jest-utils. Unfortunately the private method this._bindExposedWorkerMethods() of the Worker class has to become async, but it is called in the constructor. Async calls are not possible in constructors.

Good news: Worker is a named export. If I get it right, this makes it possible to export something else from jest-worker. So perhaps an asynchronous createWorker() factory function could be a non-breaking solution?

import {createWorker} from 'jest-worker';

const workerPath = new URL('./testWorker.js', import.meta.url).pathname;

const worker = await createWorker(workerPath);

@SimenB Does it look acceptable for you? Feels like I could solve it this way.

Expected behavior

Would be great to support ESM worker modules in jest-worker package.

Actual behavior

jest-worker package does not support ESM worker modules.

Additional context

No response

Environment

System:
    OS: macOS 10.15.7
    CPU: (8) x64 Intel(R) Core(TM) i7-3615QM CPU @ 2.30GHz
Binaries:
    Node: 17.3.1 - ~/.nvm/versions/node/v17.3.1/bin/node
    Yarn: 2.4.3 - /usr/local/opt/node@16/bin/yarn
    npm: 8.3.0 - ~/.nvm/versions/node/v17.3.1/bin/npm
npmPackages:
    jest: workspace:* => 27.4.7

[SimenB]

@SimenB Does it look acceptable for you? Feels like I could solve it this way.

yes! factory pattern is how we’ve solved other “class does require in constructor, we need await import”

[SimenB]

yay!