[Bug?]: Yarn pnp / sdk generation doesn't work with ESLint new flat config support

[dbaeumer]

Self-service

• I'd be willing to implement a fix

Describe the bug

ESLint's new flat config support fails to load when using flat config module files. It does work when using common JS config files.

This bahviour gor reported against the VS Code ESLint extension (see microsoft/vscode-eslint#1620) but it is independent of the VS Code extension and can be reproduce using the eslint npm package standalone

To reproduce

Setup:

package.json

{
  "name": "yarn-eslint-test",
  "packageManager": "yarn@4.1.1",
  "type": "module",
  "scripts": {
    "eslint": "eslint test.js"
  },
  "devDependencies": {
    "@eslint/js": "^8.57.0",
    "eslint": "^8.57.0"
  }
}

eslint.config.mjs

import js from "@eslint/js";

export default [
	js.configs.recommended,
	{
		files: ["**/*.js"],
		rules: {
			"no-var": "error",
		}
	}
];

test.js

var x = 10;

Run the following commands in a shell:

> corepack enable
> yarn install
> yarn dlx @yarnpkg/sdks vscode
> export NODE_PATH=".yarn/sdks"

Setting the NODE_PATH is equivalent to setting the VS Code eslint.nodePath setting.

start node REPL and execute the following commands (to ensure to mimic the executing since a VS Code extension):

require.resolve('eslint');

We will load the eslint npm module from .yarn/sdks

const library = require('eslint');

async function main() { const eslint = new (await library.loadESLint({ useFlatConfig: true }))(); const report = await eslint.lintText(`var test = "hello";`); console.log(report); }

main().catch((error) => { console.error(error); process.exitCode = 1; });

You get:

Expected behavior: the eslint.config.mjs can successfully be loaded. Converting the config file to cjs makes everything work.

Environment

System:
OS: Linux 5.15 Ubuntu 22.04.4 LTS 22.04.4 LTS (Jammy Jellyfish)
CPU: (20) x64 12th Gen Intel(R) Core(TM) i7-12700K
Binaries:
Node: 18.18.2 - /tmp/xfs-e72dc863/node
Yarn: 4.1.1 - /tmp/xfs-e72dc863/yarn
npm: 9.8.1 - ~/.nvs/default/bin/npm

Additional context

No response

[dbaeumer]

Any news on this. This issue is basically blocking flat config adaption with VS Code / eslint extension.

[arcanis]

I'm looking right now at migrating this repository to Eslint 9; I'll take a look at that at the same time.

[arcanis]

I'm experimenting in #6278 - it seems to work with your (very detailed, thanks a lot!) reproduction, but it still fails in VSCode. Trying to figure out what might be different.

[arcanis]

I think I figured it out - v18.19.0 is the first version that supports register (to add ESM loaders at runtime), and VSCode ships with Electron 28, which is tied to Node 18.18. So unfortunately I'm afraid we can't do much right now 🫤

[dbaeumer]

@arcanis thanks for looking into this.

Which node version is required to make this work. I tested the same steps under Node 20.10.0 and it produces the same exception.

[arcanis]

You need both my PR (#6278) and Node >v20.6.0, v18.19.0; you can try it by cloning my branch and running your repro in this repo.

[dbaeumer]

Thanks!

We will move to Electron 29 in the near future which will come with NodeJS 20.x