#20357 implemented sourceCode.markVariableAsUsed method. However, it has some shortcomings.

At present it doesn't communicate back to Rust that the variable is marked as used, so Rust rules like no-unused-vars will not take that into account.

Fixing this will be difficult. Currently JS rules run after Rust rules, so by the time a var is marked as used, it's too late for no-unused-vars. Only solution is to make JS rules run first, but that's hard as the AST is mutated to convert UTF-8 spans to UTF-16 before sending to JS, and that would not work on Rust side, as Rust uses UTF-8 strings.

Workaround

If it's essential for no-unused-vars to receive the signals from markVariableAsUsed, the only current solution is to run the original ESLint no-unused-vars rule as a JS plugin:

{
  "jsPlugins": ["oxlint-plugin-eslint"],
  "rules": {
    "eslint-js/no-unused-vars": "error"
  }
}

(note the eslint-js prefix on the rule name)