This upgrade is going to be a lot of work, because it brings a breaking change for plugins and our configuration. So we need to upgrade each and every plugin to a version that supports eslint v9, and then we will need to rewrite our configuration file to the new "flat config" format.

Here is a list of our plugins where maintainers have released versions compatible with v9:

vue-eslint-parser

Upgrade: [] Support: ☑ https://github.com/vuejs/vue-eslint-parser/releases/tag/v10.0.0

eslint-plugin-you-dont-need-lodash-underscore

Upgrade: [] Support: ❌ https://github.com/you-dont-need/You-Dont-Need-Lodash-Underscore/issues/396

We could do the work to contribute the support for flat config & v9, or we could decide to drop this plugin. Usage of lodash has been drastically reduced.

eslint-plugin-monorepo-cop

Upgrade: [] Support: ❌ https://github.com/sterlingwes/eslint-plugin-monorepo-cop/issues/9

We could do the work to contribute the support for flat config & v9, or we need to find an alternative. We still want to forbid relative imports.

eslint-plugin-no-unsanitized

Upgrade: [] Support: ☑ https://github.com/mozilla/eslint-plugin-no-unsanitized/commit/d9704a7e402c7f95e31b4f97a8c192afdcfe1994

eslint-plugin-no-only-tests

Upgrade: [x] Support ☑

Release v3.3.0

eslint-plugin-storybook

Upgrade: [x] Support ☑ https://github.com/storybookjs/eslint-plugin-storybook/blob/v0.10.0/CHANGELOG.md#v0100-mon-oct-21-2024

Changelog for v0.12.0

eslint-plugin-jest

Upgrade: [x] Support ☑

• Changelog for v28.0.0
• Changelog for v28.14.0

eslint-plugin-import

Upgrade: [x] Support ☑ https://github.com/import-js/eslint-plugin-import/issues/2556

Changelog for v2.31.0

eslint-plugin-vue

Upgrade: [] Support ☑ https://github.com/vuejs/eslint-plugin-vue/issues/1291

typescript-eslint

Upgrade: [] Support ☑ https://github.com/typescript-eslint/typescript-eslint/issues/8211

• Changelog for v7.x
• Changelog for v8.x
• Blog post for v8.x
• Changelog for v8.34.1

eslint-plugin-cypress

Upgrade: [x] Support ☑ https://github.com/cypress-io/eslint-plugin-cypress/issues/146

• Release v3.0.0
• Release v3.2.0
• Release v3.3.0
• Release v3.6.0

eslint-plugin-prettier

Upgrade: [] Support ☑ https://github.com/prettier/eslint-plugin-prettier/issues/591

eslint

Upgrade: [x] 8.52.0 -> 8.57.0

• Changelog for v8.57.0 - This enables us to upgrade plugins like eslint-plugin-jest that only keep compatibility with the last eslint 8.x version.

Useful links:

• https://eslint.org/docs/latest/use/configure/configuration-files-new
• https://github.com/prettier/eslint-config-prettier#eslintconfigjs-flat-config-plugin-caveat
• https://eslint.org/docs/latest/use/configure/migration-guide
• https://eslint.org/docs/latest/use/configure/migration-guide#cli-flag-changes
• https://eslint.org/docs/latest/use/migrate-to-9.0.0#flat-config