Upgrade eslint to version 9.0.0

[timvandermeij]

We should upgrade to ESLint 9 now that it's officially released. The changelog, including the breaking changes that should be audited, can be found at https://github.com/eslint/eslint/releases/tag/v9.0.0. Note that this upgrade is currently blocked on the ESLint plugins that we use indicating support for ESLint 9 in their package.json ranges first, so this is mostly a tracking issue at the moment.

[wojtekmaj]

Let's make it a tracking issue then :D

Plugins

Plugin name	Update status	Development status	Issue	Comments
eslint-plugin-import		❓ Probably planned	import-js/eslint-plugin-import#2948	Worth considering a switch to eslint-plugin-import-x, much more reasonably maintained alternative
eslint-plugin-json		✅ Implemented	azeemba/eslint-plugin-json#80	Update blocked by eslint-plugin-mozilla support for v4.0.0
eslint-plugin-mozilla		❓ Probably planned	https://bugzilla.mozilla.org/show_bug.cgi?id=1881696
eslint-plugin-no-unsanitized		⌛ Planned	mozilla/eslint-plugin-no-unsanitized#234	Development blocked by typescript-eslint
eslint-plugin-sort-exports		❓ Unknown	n/a
eslint-plugin-unicorn	✅ d7f2bc0	✅ Implemented	sindresorhus/eslint-plugin-unicorn#2250

[timvandermeij]

In commit d7f2bc0 eslint-plugin-unicorn got upgraded to version 53.0.0 which contains support for ESLint 9, so we can cross that one off the list.

[nicolo-ribaudo]

If you haven't already seen https://eslint.org/blog/2024/05/eslint-compatibility-utilities/, it might be useful for this. It provides wrappers to run ESLint 8 plugins in ESLint 9.

[mozfreddyb]

I can comment for eslint-plugin-no-unsanitized: It's planned but blocked on dependencies (heh)
mozilla/eslint-plugin-no-unsanitized#241

[timvandermeij]

eslint-plugin-json 4.0.0 is now released and contains ESLint 9 support (see azeemba/eslint-plugin-json@0ff302c), but we can't update to it yet because eslint-plugin-mozilla has not indicated support for version 4.0.0 in package.json yet:

npm error While resolving: eslint-plugin-mozilla@3.7.4
npm error Found: eslint-plugin-json@4.0.0
npm error node_modules/eslint-plugin-json
npm error   dev eslint-plugin-json@"^4.0.0" from the root project
npm error
npm error Could not resolve dependency:
npm error peer eslint-plugin-json@"^3.1.0" from eslint-plugin-mozilla@3.7.4
npm error node_modules/eslint-plugin-mozilla
npm error   dev eslint-plugin-mozilla@"^3.7.4" from the root project
npm error
npm error Conflicting peer dependency: eslint-plugin-json@3.1.0
npm error node_modules/eslint-plugin-json
npm error   peer eslint-plugin-json@"^3.1.0" from eslint-plugin-mozilla@3.7.4
npm error   node_modules/eslint-plugin-mozilla
npm error     dev eslint-plugin-mozilla@"^3.7.4" from the root project