Updating eslint to 9 causes dev server errors.

[JustFly1984]

Preliminary Checks

• This issue is not a duplicate. Before opening a new issue, please search existing issues: https://github.com/gatsbyjs/gatsby/issues
• This issue is not a question, feature request, RFC, or anything other than a bug report directly related to Gatsby. Please post those things in GitHub Discussions: https://github.com/gatsbyjs/gatsby/discussions

Description

I've tried to update eslint to 9, with new flat config.VSCode and cli works good, but then I'm trying to run dev, it fails with error.
Looking at documentation, disabling eslint with empty .eslintrc doesn't help.

Error:

 ERROR #98123  WEBPACK.DEVELOP

Generating development JavaScript bundle failed

Invalid Options:
- Unknown options: extensions, rulePaths, useEslintrc
- 'extensions' has been removed.
- 'rulePaths' has been removed. Please define your rules using plugins.

failed Building development bundle - 3.210s
ERROR in Invalid Options:
- Unknown options: extensions, rulePaths, useEslintrc
- 'extensions' has been removed.
- 'rulePaths' has been removed. Please define your rules using plugins.

develop compiled with 1 error

Reproduction Link

don't have a repro

Steps to Reproduce

1. Update eslint and plugins to latest
2. Run migration eslintrc to mjs https://eslint.org/docs/latest/use/configure/migration-guide
3. Run eslint in cli, to check if config is correct.
4. Run gatsby develop - you will get an error

Expected Result

Dev server should be decoupled from eslint version.
Gatsby should support eslint@9 and flat config.

Actual Result

Error:

 ERROR #98123  WEBPACK.DEVELOP

Generating development JavaScript bundle failed

Invalid Options:
- Unknown options: extensions, rulePaths, useEslintrc
- 'extensions' has been removed.
- 'rulePaths' has been removed. Please define your rules using plugins.

failed Building development bundle - 3.210s
ERROR in Invalid Options:
- Unknown options: extensions, rulePaths, useEslintrc
- 'extensions' has been removed.
- 'rulePaths' has been removed. Please define your rules using plugins.

develop compiled with 1 error

Environment

System:
    OS: macOS 14.5
    CPU: (10) arm64 Apple M1 Max
    Shell: 3.2.57 - /bin/sh
  Binaries:
    Node: 22.4.0 - /tmp/yarn--1720005845909-0.247377011876049/node
    Yarn: 1.22.22 - /tmp/yarn--1720005845909-0.247377011876049/yarn
    npm: 10.8.1 - ~/.nvm/versions/node/v22.4.0/bin/npm
  Browsers:
    Chrome: 126.0.6478.127
    Safari: 17.5
  npmPackages:
    gatsby: 5.13.6 => 5.13.6
    gatsby-link: 5.13.1 => 5.13.1
    gatsby-plugin-catch-links: 5.13.1 => 5.13.1
    gatsby-plugin-dts-css-modules: 3.0.0 => 3.0.0
    gatsby-plugin-minify-classnames: 5.0.0 => 5.0.0
    gatsby-plugin-postcss: 6.13.1 => 6.13.1
    gatsby-plugin-purgecss: 6.2.1 => 6.2.1
    gatsby-plugin-root-import: 2.0.9 => 2.0.9
    gatsby-plugin-sass: 6.13.1 => 6.13.1
    gatsby-plugin-sitemap: 6.13.1 => 6.13.1
    gatsby-plugin-typescript: 5.13.1 => 5.13.1
    gatsby-react-router-scroll: 6.13.1 => 6.13.1
    gatsby-script: 2.13.0 => 2.13.0

Config Flags

No response

[Austaras]

As a workaround, you can create a empty .eslintrc to disable eslint-loader. A proper fix is possible, but with the current status of gatsby, it would take some time.

[JustFly1984]

I've tried the workaround, gatsby still crashes

[justinchan23]

i resolved this issue by the following:

1. npm install --save-dev gatsby-plugin-eslint eslint eslint-webpack-plugin eslint-config-react-app
2. create an empty .eslintrc.js file in the root dir

linting still works using the cli but may not appear in the running gatsby process .

alternatively if the above doesnt fix your dev server you can just build and serve the app (not ideal but was a workaround for me)

[amalitsky]

Could not figure this one out. Already had .eslintrc.js in place.
Rolled eslint back to v.8.57.1.

[kunalyadav684]

Yes same for me, after creating empty .eslintrc.js file getting below error