Add the ignoreRestSiblings option into correctness/noUnusedVariables

[iamakulov]

Qq: may I request to add the ignoreRestSiblings: boolean option into correctness/noUnusedVariables, like ESLint does?

Until #1910, Biome was behaving as if this option was always set to false. #1910 changed Biome to behave as if this option is always true. However, I believe the preferred behavior is different in different codebases, and I’d love the ability to configure this explicitly.

More context

A common pattern to omit keys from an object is to spread it like so:

const car = { brand: "Tesla", year: 2019, countryCode: "US" }

// Remove model & year keys from the object
const { brand, year, ...other } = car

// Use the new object
formatCar(other)

Until 2024, in the code above, correctness/noUnusedVariables would (correctly) flag model and year as unused variables. #572 and #1910 changed that, disabling the lint for unused spread members. While this addressed the use case from #572, this made other use cases worse. To give a simplified example:

function Car(props) {
  const { brand, year, ...otherProps } = props

  if (brand === "Audi") {
    if (year === undefined || year < 2016) return <AudiCar salesStats={genericSalesStats} {...otherProps} />
    return <AudiCar salesStats={audiSalesStats} {...otherProps} />
  } else if (brand === "Tesla") {
    if (year === undefined || year < 2021) return <TeslaCar salesStats={genericSalesStats} {...otherProps} />
    return <TeslaCar salesStats={teslaSalesStats} {...otherProps} />
  }
  // ...
}

Say I refactor this code and move the whole year logic into AudiCar, TeslaCar, and so on. However, in the process, I forget to remove year from the destructuring on line 2. TypeScript wouldn’t catch this because the year prop is allowed be undefined. And as of #1910, correctness/noUnusedVariables wouldn’t catch this either. This would result in a likely bug.

Ultimately, this boils down to preferences. The author of #572 would prefer to omit properties from objects without any extra visual noise. We at Framer would instead prefer correctness; if you’re not using destructured properties because you want to omit them, you better make it explicit (e.g. with an // biome-ignore, or by prefixing the destructured var with a _). So: may I ask to add an explicit option like ignoreRestSiblings?

[ematipico]

Sounds like a nice suggestion! PRs are welcome 🤗

[iamakulov]

Raised! #5157