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: support unknown
• [] ❌ eslint-plugin-you-dont-need-lodash-underscore 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-no-unsanitized https://github.com/mozilla/eslint-plugin-no-unsanitized/commit/d9704a7e402c7f95e31b4f97a8c192afdcfe1994
• [x] ☑ eslint-plugin-no-only-tests https://github.com/levibuzolic/eslint-plugin-no-only-tests/releases/tag/v3.3.0
• ☑ eslint-plugin-storybook https://github.com/storybookjs/eslint-plugin-storybook/blob/main/CHANGELOG.md#v0100-mon-oct-21-2024
• [] ☑ eslint-plugin-jest https://github.com/jest-community/eslint-plugin-jest/blob/main/CHANGELOG.md#2800-2024-04-06
• [] ☑ eslint-plugin-import https://github.com/import-js/eslint-plugin-import/issues/2556
• [] ☑ eslint-plugin-vue https://github.com/vuejs/eslint-plugin-vue/issues/1291
• [] ☑ typescript-eslint https://github.com/typescript-eslint/typescript-eslint/issues/8211
• [] ☑ eslint-plugin-cypress https://github.com/cypress-io/eslint-plugin-cypress/issues/146
• [] ☑ eslint-plugin-prettier https://github.com/prettier/eslint-plugin-prettier/issues/591

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