[New] check unused rules with overrides

[nicolaichuk]

Fixes #317.

[ljharb]

Can you help me understand what this PR is doing? Would, for example, @scope/scoped-plugin/foo-rule be included in the unused rules list without this fix?

[MichaelDeBoey]

@nicolaichuk Is there something I can help with in order to get this one merged?

[ljharb]

Answering the question i asked above would help.

[MichaelDeBoey]

@ljharb This PR will make it possible to have an .eslintrc like

module.exports = {
  rules: {},
  overrides: {
    files: ['**/__tests__/**/*.+(js|ts)?(x)'],
    rules: {
      'jest/no-conditional-expect': 'error',
    },
  },
}

instead of needing to first disable it

module.exports = {
  rules: {
     'jest/no-conditional-expect': 'off',
  },
  overrides: {
    files: ['**/__tests__/**/*.+(js|ts)?(x)'],
    rules: {
      'jest/no-conditional-expect': 'error',
    },
  },
}

And still have --unused flag pass.

This will make the jest config of eslint-config-kentcdodds doesn't have to use a workaround
https://github.com/kentcdodds/eslint-config-kentcdodds/blob/ef7069e100e932be165115f1d03b5d76a797cf04/jest.js#L137-L141

[ljharb]

Great, thanks for explaining.

[codecov-commenter]

Codecov Report

Merging #343 (6dabfb7) into master (bc5a855) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #343   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            9         9           
  Lines          185       185           
=========================================
  Hits           185       185           

Impacted Files	Coverage Δ
src/lib/rule-finder.js	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update bc5a855...6dabfb7. Read the comment docs.

[MichaelDeBoey]

@ljharb Thanks for merging!

Can you please cut a release?

[ljharb]

That takes a bit longer due to requiring a review from another collaborator.

[MichaelDeBoey]

Please ping me when it's released

[ljharb]

v4.1.0 is released

[nicolaichuk]

@ljharb, @MichaelDeBoey

Thanks.