no-unused-vars false positive in for-in loops? still an issue?

Tell us about your environment

Node version: v12.18.3
npm version: v6.14.8
Local ESLint version: v7.7.0 (Currently used)
Global ESLint version: Not found
Done in 10.47s.

What parser (default, @babel/eslint-parser, @typescript-eslint/parser, etc.) are you using? None?

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

I’m a contributor to https://github.com/streamich/git-cz and was trying to get this PR approved: https://github.com/streamich/git-cz/pull/171

As you can see its failing. Then I decided to reproduce the PR by upgrading the ESLint version locally, run ESLint, and see what the output was locally, and its the same as the build server:

/home/travis/build/streamich/git-cz/lib/cli.js
  81:16  error  'key' is defined but never used  no-unused-vars
/home/travis/build/streamich/git-cz/lib/getConfig.js
  16:14  error  'file' is defined but never used  no-unused-vars
✖ 2 problems (2 errors, 0 warnings)

So I decided to take a look at the problematic files/lines:

cli.js

// eslint-disable-next-line guard-for-in
    for (const key in passThroughParams) {
      const value = passThroughParams[key];

      if (key.length === 1) {
        appendedArgs.push('-' + key);
      } else {
        appendedArgs.push('--' + key);
      }

      if (value !== true) {
        appendedArgs.push(value);
      }
    }

getConfig.js

for (const file of configFiles) {
    const filename = path.resolve(dir, file);

    if (fs.existsSync(filename) && fs.statSync(filename).isFile()) {
      return require(filename);
    }
  }

as you can see 👀 both variables are definitely used right after being declared.

What did you expect to happen?

Not to get those 2 errors. everything should pass.

What actually happened? Please include the actual, raw output from ESLint.

/home/travis/build/streamich/git-cz/lib/cli.js
  81:16  error  'key' is defined but never used  no-unused-vars
/home/travis/build/streamich/git-cz/lib/getConfig.js
  16:14  error  'file' is defined but never used  no-unused-vars
✖ 2 problems (2 errors, 0 warnings)
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
The command "yarn lint" exited with 1.

Are you willing to submit a pull request to fix this bug? not really because supposedly this was already fixed in #12117 and I have no idea why it’s happening again.

Some extra steps that I think you can run to have a good example of this happening:

git clone https://github.com/streamich/git-cz
cd git-cz
npm i
npm i eslint@latest #to update from eslint 4 to 7
npm run eslint #runs the eslint task/script
#get errors :joy: 

Then you can open the files it complains about and play with them to try to fix it.

Related issues: #13163 and #12117 Supposedly this was fixed but somehow it’s happening in this code/project as you can see… and we don’t use babel…

Have a nice day! 🤗

[mdjermanovic]

It seems that the project is using an older version of babel-eslint.

.eslintrc.json in streamich/git-cz extends mailonline config, which sets "parser": "babel-eslint", and has "babel-eslint": "^8.0.2" as a dependency.

Upgrading babel-eslint will probably solve the issue.

[rodrigograca31]

Thank you. Sorry for creating a duplicated issue. I wasn’t aware that this project required another one that required babel-eslint. 🤔