ESLint 6.2.0 + babel-eslint + no-unused-vars false positive with for-in loop

[feross]

There's a new issue in ESLint 6.2.0 just caught by the standard test suite. This may be an issue with babel-eslint, though I am not sure since the issue did not exist in ESLint 6.1.0. Here's a pointer to the issue I filed with ESLint: eslint/eslint#12117

[yyfearth]

Seems the eslint-scope is outdated for the latest eslint.

[jharris4]

FYI I tried upgrading eslint-scope to latest on my fork of this package, and the false positives are still happening.

[DullReferenceException]

Maybe related, having the same problem with for..of loops:

import scenarios from './scenarios';

for (const scenario of scenarios) {
  doSomethingWithScenario(scenario);
}

Get an eslint error:

'scenario' is defined but never used. eslint(no-unused-vars)

With eslint@6.2.0 and babel-eslint@10.0.2.

eslint@6.1.0 works.

[yyfearth]

According to the original eslint issue eslint/eslint#12117

Most likely it is that commit, with babel-eslint in the keyword example there is a TDZ scope between function and for, probably because it's using the old version of eslint-scope

[feross]

Just wanted to note that ESLint 6.2.1 contains an important security fix (see: https://eslint.org/blog/2019/08/eslint-v6.2.1-released) but it's not possible to upgrade to 6.2.0 or later until this issue is fixed.

[JLHwung]

For those who are curious about why ESLint 6.2 + babel-eslint does not work and how we may solve it on babel-eslint side, I have written a bit on #793 (comment).

[hzoo]

Ok merged #794 thanks to everyone and @JLHwung for the PR, released as 10.0.3. Not an easy package to maintain for sure given it's patching the packages themselves. Ideally we'll have better hooks for these things in the future.

Can also do one for v11 beta.

I verifed with one of the test cases on 10.0.2 and it failing and passing with 10.0.3. Let us know if this issue still persists! Thanks!