Support for eslint v9

[pnodet]

Summary

Eslint has introduced a new config files system called flat config and using eslint.config.js.

As per the documentation:

Warning
We are transitioning to a new config system in ESLint v9.0.0. The config system shared on this page is currently the default but will be deprecated in v9.0.0. You can opt-in to the new config system by following the instructions in the documentation.

I migrated my config to the flat system but nextjs doesn't picked it up when calling next lint.

From next.js/packages/next/src/cli/next-lint.ts

    // Find user's .eslintrc file
    // See: https://eslint.org/docs/user-guide/configuring/configuration-files#configuration-file-formats
    const eslintrcFile =
      (await findUp(
        [
          '.eslintrc.js',
          '.eslintrc.cjs',
          '.eslintrc.yaml',
          '.eslintrc.yml',
          '.eslintrc.json',
          '.eslintrc',
        ],
        {
          cwd: baseDir,
        }
      )) ?? null

Additional information

No response

Example

No response

[pnodet]

Any update on this?

The flat config will be the de facto standard but I can't make it work when running next lint.

Saw a PR (#56181) but doesn't seem to be active...

[z0n]

ESLint 9 is now out and it's not compatible with next lint at all:

$ next lint
Invalid Options:
- Unknown options: useEslintrc, extensions, resolvePluginsRelativeTo, rulePaths, ignorePath, reportUnusedDisableDirectives
- 'extensions' has been removed.
- 'resolvePluginsRelativeTo' has been removed.
- 'ignorePath' has been removed.
- 'rulePaths' has been removed. Please define your rules using plugins.
- 'reportUnusedDisableDirectives' has been removed. Please use the 'overrideConfig.linterOptions.reportUnusedDisableDirectives' option instead.

If you get these errors, downgrade to ESLint 8.

[manuelbachl]

I get these exact messages right AFTER downgrading to ESLint 8...
Before I had the problem with the patch.

[kaungmyatlwin]

If you have [email protected], update to eslint^9. This solved for me.

[infodusha]

As a temporary solution you can skip eslint on build via config and run it manually. You have to reconfigure all the plugins to use flat config tho.

[dzienisz]

imho it should be updated in next 14

[developedbyumair]

downgrade is not a solution

[poksme]

This will not make Next.js pickup your config file, but I wrote a guide on how to migrate to ESLint 9 until Next.js supports it : Eslint 9 & Next.js — Setup Guide

Also for a TLDR; check my comment here

[leerob]

ESLint 9 is supported as of the Next.js 15 RC 2. v15 stable release coming soon 🙏

https://x.com/nextjs/status/1846276572812124565

[jdhiro]

I'm still not seeing any real details or examples of how we move to the new eslint.config.js format. I've tried many things but always get:

Failed to patch ESLint because the calling module was not recognized.
If you are using a newer ESLint version that may be unsupported, please create a GitHub issue:
https://github.com/microsoft/rushstack/issues

[paschun]

Yeah, the rushstack eslint patch require() breaks it for me. I wasn't able to make @eslint/eslintrc FlatCompat work because of that line. I even tried converting my config to commonjs, because the docs say only commonjs supported, but that seems irrelevant and didn't fix it either. I ended up including eslint plugins react,react-hooks,import,jsx-ally,next myself. And just copy+pasting over the 10 or so rules that eslint-config-next provides. That's really all the config is, the recommended rules from those 5 plugins plus 10 or so modifications. The only other line that is needed is the eslint-import-resolver-typescript. All the other settings in there are superfluous or legacy cruft at this point.

next.js/packages/eslint-config-next/index.js

Line 53 in ca5f29d

require('@rushstack/eslint-patch/modern-module-resolution')

Kinda surprised this hasn't been addressed, because the changes needed to update it are so trivial. I guess the engineers at vercel aren't using eslint-config-next in the up-to-date way, that would explain it. Or if there is a general stability-fear-of-change that has taken hold.

Oh, and those 5 plugins mostly don't support flat config yet, but that can easily be worked around with something like

    plugins: { 'react-hooks': reactHooks },
    rules: reactHooks.configs.recommended.rules,

where reactHooks refers to the root default export of the plugin. Again, why is this so hard for plugin authors to do? It's so trivial, lol. Apathy? Whatever the explanation it would probably apply to both next and react plugins since several of the core React engineers are employed at Vercel.

[jdhiro]

@leerob any chance you could chime in here and let us know when there will be a sensible eslist9/nextjs config available?

[SouroucheB]

I'm exactly in the same situation, when I'm running the "next lint" in the terminal, I'm getting the rushstack issue.

Failed to patch ESLint because the calling module was not recognized.
If you are using a newer ESLint version that may be unsupported, please create a GitHub issue:
https://github.com/microsoft/rushstack/issues

Guys, what did you ended to do ? Just rollbacking to Eslint 8 or as @paschun says, copy/past the eslint-config-next config ?
TYVM.

[omermecitoglu]

I'm exactly in the same situation, when I'm running the "next lint" in the terminal, I'm getting the rushstack issue.

Failed to patch ESLint because the calling module was not recognized.
If you are using a newer ESLint version that may be unsupported, please create a GitHub issue:
https://github.com/microsoft/rushstack/issues

Guys, what did you ended to do ? Just rollbacking to Eslint 8 or as @paschun says, copy/past the eslint-config-next config ? TYVM.

#49337 (comment)

[prashantchothani]

Same for me. The reference to @rushstack/eslint-patch is coming from: node_modules/eslint-config-next/index.js. It contains require('@rushstack/eslint-patch/modern-module-resolution') which is creating an issue for eslint 9 to run. So the twitter post supporting eslint 9 is not correct I feel @leerob

[leerob]

It might be worth starting a new project with create-next-app and picking ESLint, which will use v9 (source code), and then working backwards from that example vs. your current repo.

[prashantchothani]

This is a new project. However I will try once again as suggested