Update Eslint to from v9 to v10

[SjurSutterudSagen]

There has been a new version of Eslint released since the beginning of the year, but some of the plugins we use have not been updated to support it. This has meant we have not been able to update to the new version, even though it is maybe 5+ months since it was released.

We need to sit down and go through the plugins and really consider if we should change to something else.

Dependabot PR for the update: #1340

I think there is atleast one more plugin holding us back than the one mentioned in that pull request, so we need to look for alternatives to that one too.

Eslint v9 EOL is 2026-08-06
https://eslint.org/version-support/

[SjurSutterudSagen]

Eslint dependency	Supports Eslint 10
eslint-config-prettier	❓Unsure. 1 year since last release. Support may not be needed since all it does it turn rules off? Official Prettier plugin
eslint-plugin-import	❌ Fix merged to main, but unreleased. Only installed, not wired up in our config? Unused?
eslint-plugin-jsx-a11y	❌ PR opened, no comment from maintainer in it. Seems unmaintained. Only installed, not wired up in our config? Unused?
eslint-plugin-react	❌ PR in progress. Needs the fix from eslint-plugin-import
eslint-plugin-react-hooks	✅ Since 7.1.0 Official react plugin
eslint-plugin-storybook	✅ Since 10.3.0
eslint-plugin-unused-imports	✅ Since 4.4.0 but relies on eslint-plugin-react
PxWeb2-ui/eslint-plugin-storybook	✅ Since 10.3.0

A few things to note:

• We need to decide if we want to use the unused plugins or not. If not, then remove them.
• Do we need both eslint-plugin-storybook? Maybe we tried moving it to root, but updating with the Storybook CLI re-added it in pxweb2-ui?
• The unsupported plugins are all maintained by the same maintainer. He has been working on fixes, but it seems to go quite slow. I think it is unlikely that they will be updated with support before Eslint 9 is EOL on 6th August, ref: https://eslint.org/version-support/.

The biggest hurdle seems to be eslint-plugin-react,

[SjurSutterudSagen]

Eslint v9 is EOL today. Discussed it with @PerIngeVaaje and we decided to wait a little while longer to see if gets unblocked in the near future.

If not, a potential alternative can be to use https://www.npmjs.com/package/@eslint-react/eslint-plugin instead of eslint-plugin-react, and just check to see if all the rules we use are supported. It is not a fully drop-in replacement.

[SjurSutterudSagen]

Discussed this internally in Norway, and we think there is so much noise around this now that it is better to test removing the problem packages. At least for a while.