Adding support for eslint.config.mjs and eslint.config.cjs files.

[yittoo]

I am not sure if it is something that you do want to do until FlatConfig is final. But for cases where we want to use eslint.config.mjs we are adding a workspace overwrite as follows. I think this could be extended in the extension source code.

"eslint.options": {
  "overrideConfigFile": "eslint.config.mjs"
}

I can help with the code adjustment if this feature is desired. Cheers.

[dbaeumer]

How does that work when using ESLint on the command line?

[yittoo]

@dbaeumer with ESLINT_USE_FLAT_CONFIG=true eslint -c eslint.config.mjs cli flag

edit: also there is a workaround which is briefly mentioned here #1518 (comment)

[dbaeumer]

Since this is a command line option you need to use eslint.options to point to a different config file than the default one. I am reluctant to add any code to detect and choose config files besides that standard behavior of eslint npm package.

I will close the issue since this is the expected behavior.

[itpropro]

@dbaeumer eslint.config.js is considered the new standard and the .eslint options as legacy reference. I would definitely see it as a bug in this VSCode extension, if the default way of writing eslint configs would not be detected by default. Especially as I have not worked on a JS/TS project for months that still used the legacy syntax.

[dbaeumer]

The extension detects by default anything that the eslint npm module (https://www.npmjs.com/package/eslint) uses as default. I don't have any special code that detects the config file. This is why I said if you need to pass -c on the command line you need to let the extension know the same via eslint.options

[jamielaw-jellyfish]

I'm encountering a related issue.

Steps to reproduce:

Start a new blank project with the following package.json

{
  "scripts": {
    "lint": "eslint ."
  },
  "devDependencies": {
    "eslint": "^8.51.0"
  },
  "type": "module"
}

eslint.config.js

export default [
  {
    rules: {
      semi: "error",
    }
  }
];

and index.js

const foo = 42

VS Code gives no red underlines inside of index.js but running npm run lint will output the following errors in the console:

/Users/jamielaw/projects/linting/index.js
  1:15  error  Missing semicolon  semi

✖ 1 problem (1 error, 0 warnings)
  1 error and 0 warnings potentially fixable with the `--fix` option.

Switching eslint.config.js to the following .eslintrc.js

module.exports = {
  env: {
    es6: true
  },
  rules: {
    semi: 'error'
  }
};

and VS Code will highlight code errors automatically as expected. So, ESLint seems to understand the new config file format, but VS Code isn't picking it up.

[yittoo]

@jamielaw-jellyfish If i am not mistaken this feature is experimental still (or perhaps recently moved to stable?). Maybe the following will help fix it.

.vscode/settings.json

{
  "eslint.experimental.useFlatConfig": true
}

[jamielaw-jellyfish]

@yittoo It did not work in this case, at least not for me.

However, just knowing that in time it will be available is good enough. For the time being, I will keep using the old config format, but keep an eye out for when support for the new format becomes publicly available. :-)

[dbaeumer]

@jamielaw-jellyfish can you please provide me with a Github repository I can clone that demos this. This ensures we are looking at the same problem since things like this depend on many variables.

[jamielaw-jellyfish]

@dbaeumer Here you go:

https://github.com/jamielaw-jellyfish/eslint-config-test

[dbaeumer]

Could it be that you have something globally installed. Running npm run lint fails for me like this:

[jamielaw-jellyfish]

I realise the error I made in the repo: .eslint.config.js should not have a leading dot. Remove that and the command line should find the config file.

[dbaeumer]

Works for me as expected in VS Code

Anything special in the ESLint otuput log?

[jamielaw-jellyfish]

So, I have been able to get it working, I think. Here was my process:

1. I updated VS Code. I was on 1.83.0 before and now I am on 1.83.1
2. I restarted the ESLInt Server. Without .vscode/settings.json I got errors in the ESLint output log that no config file could be found. Adding the file was enough to get it working.

So, I think the solution was to add the file, but also to restart ESLint and/or VS Code.

Sorry for taking you down this rabbit hole.

[dbaeumer]

No problem. Happy to hear you could solve it.