Change Request: Don't set `languageOptions.sourceType` (for ESLint 9)

[simonhaenisch]

eslint-plugin-n version

17.10.2

What problem do you want to solve?

https://eslint-online-playground.netlify.app/#eNpVjjsOwjAQRK9ibZMGzKfh13ILlsKy15HBXltxQJGi3J04SUHanfd2pofc6B11KiRPMrwyXMGFFJtW2CxsE4OobK5gA5S941bqyNbVa5KjoZnFBdsm/6kdbxnhhoxM3QQasurjW/FAFpO1vMuPynrV7hrSMQRiQ6Z6Ij9Hd2xOSr9VTfKVI4+lfZERDH3vlArL2lFGuIopKdk8opwQLvIs9wibdfY3sECHkzzs5RGhUAPyAMMPStleUQ==

☝️ gives

Parsing error: 'import' and 'export' may appear only with 'sourceType: module'

even though the file is using .mjs extension. After some digging I found the problem is this plugin's config which enforces languageOptions.sourceType: 'commonjs' for all files. ESLint 9 already sets the sourceType correctly based on type field in package.json and file extensions (.js/.cjs/.mjs), so there's no need for this plugin to configure this.

What do you think is the correct solution?

Don't set sourceType in language options and let ESLint handle this instead... see this playground where I removed the field from the config object and then it works fine.

https://eslint-online-playground.netlify.app/#eNpdkDFPAzEMhf9K5OWWNm1ZgCLEwo6E2GqGKHFOKYkTXXKoqLr/ziVXCdrV73vPfj5DHvSGTiokTzIcM+zBhRSHImwWdohBdDZ3sALK3nGROrJ1/TXJ0dDC4gVbJz/2jteM8ISMPLvywr2TjiEQGzLiuU0ukfnQWa/KZvgDus9mNuSp0K1besX9qHp6S8XN8S8yx3HQ9PGTqNno1I4zZNXoizggi9sM5LphLpeU/pqj5DFHnnudK4tg6PuVUiVZO8oIe9GUqi096wjhUT7ILcLqWvv3gwrt7uVuK+8QKjUhTzD9AiiihF8=

Participation

• I am willing to submit a pull request for this change.

Additional comments

Not sure if it's the same for ESLint 8.

[scagood]

I think I agree here.

---

Maybe its worth making the flat/mixed-esm-and-cjs config the recommended one 🤔

playground example

---

Thoughts @aladdin-add and @voxpelli?

This is also possibly related to #300

[voxpelli]

Yeah, I think #300 should be the recommended one

[voxpelli]

I'm running something similar to #300 in my own projects: https://github.com/voxpelli/eslint-config/blob/9eb2261fd1e0b91bea570bd83811911cf23849f6/base-configs/node.js#L12

[simonhaenisch]

Just tried

import node from 'eslint-plugin-n'

const nodeRecommended = node.configs['flat/mixed-esm-and-cjs']

nodeRecommended.forEach(config => delete config.languageOptions?.sourceType)

export default [
 ...nodeRecommended,
 // more stuff
]

and that works fine for me (.js files based on type field in package.json, and .cjs/.mjs fixed to CommonJS/ESM respectively).

So I'm also for making mixed-esm-and-cjs the actual recommended config.

I'd also drop the languageOptions.sourceType config, however I'm not sure if ESLint 8 also sets that correctly already.

[ohadschn]

import node from 'eslint-plugin-n'

const nodeRecommended = node.configs['flat/mixed-esm-and-cjs']

nodeRecommended.forEach(config => delete config.languageOptions?.sourceType)

export default [
 ...nodeRecommended,
 // more stuff
]

@voxpelli , @scagood , @simonhaenisch
What would be the equivalent workaround for pure ESM projects (not mixed)?
The same but use recommended-script instead of mixed-esm-and-cjs?

I'm also a bit confused about the spread operator (...) used in the workaround above, the docs don't include it:

const nodePlugin = require("eslint-plugin-n")

module.exports = [
    nodePlugin.configs["flat/recommended-script"],
    {
        rules: {
            "n/exports-style": ["error", "module.exports"]
        }
    }
]

[aladdin-add]

for pure esm projects (with pkg.type = "module"), just use recommneded (and it's just the same as recommended-module):

import node from 'eslint-plugin-n'

export default [
 node.configs['flat/recommended']
]

[ohadschn]

for pure esm projects (with pkg.type = "module"), just use recommneded (and it's just the same as recommended-module):

import node from 'eslint-plugin-n'

export default [
 node.configs['flat/recommended']
]

ohh so that's what the script suffix meant there... thanks!
Perhaps consider clarifying the docs a bit

[aladdin-add]

sure, PRs are always welcome! 😄

[ohadschn]

sure, PRs are always welcome! 😄

Forgive me but I barely know what I'm doing here (not a JS dev to say the least).
Took me a while to even get this config working, can't say I understand the difference between your syntax, the docs syntax, and the syntax which finally worked for me (in the previous two forms, the rules didn't actually run, I injected offenders to test):

import pluginN from 'eslint-plugin-n';

export default [
  {
    files: ['**/*.js'],
    languageOptions: {
      globals: globals.node,
      sourceType: 'module',
    },
    plugins: {
      n: pluginN,
    },
    rules: {
      ...pluginN.configs['flat/recommended'].rules,
    },
  },
];

[MikeMcC399]

I would like to see this work out-of-the box with ESLint v9 (the only currently supported version of ESLint).

With package.json having no defined type (defaults to commonjs) and eslint.config.mjs containing simply

import nodePlugin from 'eslint-plugin-n'

export default [
  nodePlugin.configs['flat/recommended'],
]

the result is:

error Parsing error: 'import' and 'export' may appear only with 'sourceType: module'

(as previously discussed above.)

Other plugins work correctly, for example:

import globals from 'globals'
import pluginJs from '@eslint/js'
import stylistic from '@stylistic/eslint-plugin'
import eslintPlugin from 'eslint-plugin-eslint-plugin'

export default [
  { languageOptions: { globals: globals.browser } },
  pluginJs.configs.recommended,
  stylistic.configs.recommended,
  eslintPlugin.configs['flat/recommended'],
]

Sorry, I don't have the understanding and confidence to fix this with a PR. Hopefully somebody else can?!