Bug: react-hooks/exhaustive-deps false positive on TypeScript generic type variable

[mschl0ss]

React version: 16.13.1

Steps To Reproduce

1. Use type generics in a useEffect.

Code example:

function useBug<T>(): void {
  useEffect(() => {
    let bug: T;
  }, []); // <-- ESLint error: React Hook useEffect has a missing dependency: 'T'.

}

The current behavior

Dependency array throws ESLint error.

React Hook useEffect has a missing dependency: 'T'. Either include it or remove the dependency array  react-hooks/exhaustive-deps

The expected behavior

No missing dependencies reported.

[sweetliquid]

Can I take this?

[sweetliquid]

@danielmiladinov

[eps1lon]

@mschl0ss We can't reproduce the reported bug with our versions of @typescript-eslint/parser and eslint-plugin-react-hooks (#20432 adds a passing test that replicates your report). Could you run npx envinfo --npmPackages '{eslint,eslint-plugin-react-hooks,@typescript-eslint/*}' --showNotFound and report back with the result?

[sweetliquid]

I built a sandbox to reproduce this problem:

[mschl0ss]

@eps1lon Running that command produced this result:

npx: installed 1 in 3.21s

After running that command I do not see the bug anymore, so I guess that did fix it. Can you explain to me what the command did? Also, why is @sweetliquid seeing the error in his sandbox?

[eps1lon]

I built a sandbox to reproduce this problem:

codesandbox might use outdated dependencies which we can't fix. If I download the codesandbox and install it I get no lint errors which hints at outdated dependencies in codesandbox.

Running that command produced this result:

It should've actually printed something more but I forgot to add an important flag: --fullTree. Could you run npx envinfo --npmPackages '{eslint,eslint-plugin-react-hooks,@typescript-eslint/*}' --showNotFound --fullTree and post the results?

[mschl0ss]

Results:

npx: installed 1 in 1.494s

  npmPackages:
    @typescript-eslint/eslint-plugin:  4.9.0
    @typescript-eslint/experimental-utils:  4.9.0
    @typescript-eslint/parser:  4.9.0
    @typescript-eslint/scope-manager:  4.9.0
    @typescript-eslint/types:  4.9.0
    @typescript-eslint/typescript-estree:  4.9.0
    @typescript-eslint/visitor-keys:  4.9.0
    eslint:  7.14.0
    eslint-plugin-react-hooks:  4.2.0

[mschl0ss]

The bug seems to have gone away. I worry that I'm giving you the false impression that the bug is being reproduced with the versions reported above.

[eps1lon]

Fairly certain this error was fixed at some point. Make sure to use the latest version of eslint-plugin-react-hooks and @typescript-eslint/parser. If the error persists please let me know and share the result of npx envinfo --npmPackages '{eslint,eslint-plugin-react-hooks,@typescript-eslint/*}' --showNotFound --fullTree

[ecraig12345]

I hit this too, and it went away after deleting old eslint caches. Something to try if anyone else happens onto this issue.