[core] Remove unused classes

[jens-ox]

Hi all!

This is just a minor addition to the eslint plugin, which detects unused classes in makeStyles declarations.
I saw that this was requested in different places (e.g. here and here).

Cheers!

Closes #23492

[mui-pr-bot]

Details of bundle changes

Generated by 🚫 dangerJS against a8b0f0e

[oliviertassinari]

Thanks for sharing. I have tried to enable it on the repository but I couldn't get it work. Any idea?

[oliviertassinari]

@jens-ox If you have time to look into the issue, please do, we would be happy to include this eslint rule :).

Now, we also plan to remove the withStyles and makeStyles, progressively (v6), so I'm closing, as it was inactive and the core have no bandwidth to look into it.

[jens-ox]

Hi @oliviertassinari! Thanks for getting back.

Could you quickly explain how I can enable it in the repository?

[oliviertassinari]

@jens-ox I had a second look at the pull request. I could make it work on the codebase, and even better remove dead classes in our demos :). However, I could also spot a couple of limitations:

• Doesn't support withStyles
• Doesn't detect when a style rule is used as a selector to increase specificity only, e.g. &$focused
• I have fixed the support of @global
• Doesn't detect when a classes is provided as a prop to another component.

In the end, I have removed the new eslint rule in a8b0f0e based on the direction we are taking with #22342. Getting this eslint rule to a great state will require a non-negligible amount of work. If you want to keep polishing, please do! It would be great to link the documentation to this eslint rule hosted under a different repository.

[jens-ox]

Just created a separate package for the rule: https://github.com/jens-ox/eslint-plugin-material-ui-unused-classes

Should I create a PR to link to it in the docs?

[oliviertassinari]

Should I create a PR to link to it in the docs?

Yes, I think that it would be interesting :)

[oliviertassinari]

@jens-ox Could you add documentation for the eslint plugin in the new repository? Regarding linking it in the docs, maybe under https://next.material-ui.com/discover-more/related-projects/#ide-tools?

[jens-ox]

Updated the docs in the repo, created PR (#23843) ☺️