Severity: Unhandled promise rejection in `whitespace-async.js` when ESLint async path is used

[dataCenter430]

Summary

When the config is loaded on ESLint 9 (or when CLIEngine is unavailable), whitespace.js runs whitespace-async.js via execSync. That script calls onlyErrorOnRules(...).then(...) with no .catch(). If the promise rejects, the rejection is unhandled.

Impact

• Process can exit with an unhandled rejection.
• Child process may write errors (or non-JSON) to stdout, so the parent’s JSON.parse(stdout) can throw and fail config loading with an unclear error.

Affected files

• packages/eslint-config-airbnb-base/whitespace-async.js (line 49)
• packages/eslint-config-airbnb/whitespace-async.js (line 49)

Suggested fix

Add a .catch() that logs the error and sets process.exitCode = 1, so rejections are handled and the child exits with a non-zero code instead of leaving an unhandled rejection.

Screenshot

I'd love to have the chance to contribute to this.

[ljharb]

I don't believe there's a released version of the config yet that works with eslint 9. However, unreleased code should, so a PR would be great - although a .catch shouldn't be the handling imo, it should just do the right thing instead.

Please be sure not to use an LLM to generate the code, since LLM-generated code is not copyrightable and thus can't be accepted to any open source project.