Refactor `no-unused-modules` to not use `FileEnumerator`

[abrahamguo]

It looks like, in #457, there's been discussion to make no-unused-modules a no-op in ESLint 10 because of the removal of FileEnumerator.

However, has there been any discussion about changing this rule to still be functional without FileEnumerator? This is a very useful rule, and it seems surprising for it to simply disappear without any alternative.

[JounQin]

Yes, the mentioned PR is a first step to support ESLint 10 easier with a warning, if there is good solution for ESLint 10, we can absolutely add it back.

[SukkaW]

There was an advantage of using the FileEnumerator at that time: ESLint could collect all the files it was supposed to lint.

The rule was on its last breath. We had been using eslint/use-at-your-own-risk and even some non-conventional ways (asking users to create a blank no-op .eslintrc file) to keep this rule alive.

This is no longer possible with ESLint 10, which now completely removes legacy config support and the FileEnumerator.

With the ESLint flat config, an ESLint plugin can no longer know what files are supposed to be included/scanned.

In fact, I highly doubt that this rule would ever come back. ESLint is not designed to do cross-file linting in the first place, and you can't easily replicate the ESLint file-scanning process with some existing libraries like fast-glob.

In the meantime, you can always use some third-party tools like knip to detect unused modules.

[silverwind]

The loss of this rule is a real shame. I tried knip before but imho it's a tool that requires far too much baby-sitting to be worth it. This rule worked flawlessly with zero config.

[SukkaW]

The loss of this rule is a real shame. I tried knip before but imho it's a tool that requires far too much baby-sitting to be worth it. This rule worked flawlessly with zero config.

The main blocking is that there is no way to obtain a "map", or "index", or "scope" of every file ESLint's flat config is currently linting.

With the ESLint legacy config, that was where FileEnumerator kicked in. But there is no replacement for ESLint's flat config.

[silverwind]

Maybe it is time to dig into eslint runtime internals to obtain the file list 😆.

[abrahamguo]

I've moved over to knip and found it to be quite good! @silverwind happy to take a look if you're having issues with it...