Bug: flat config incorrectly places sourceType

[Dremora]

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• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.
• I have searched for related issues and found none that matched my issue.
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Relevant Package

typescript-eslint

Playground Link

No response

Repro Code

Migrating from legacy to flat config started crashing ESLint on our large repository with OOM. Note that this is not related to upgrading to v7 of the package, which works fine.

I've compared final config from typescript-eslint with the regular config (converted to flat via FlatCompat) from @typescript-eslint/eslint-plugin, and the only difference is in the placement of sourceType inside the config.

ESLint Config

tseslint.configs.recommended

tsconfig

No response

Expected Result

Part of the final ESLint config:

"languageOptions": {
  "parser": {
    "meta": {
      "name": "typescript-eslint/parser",
      "version": "7.0.2"
    }
  },
  "sourceType": "module"
}

Actual Result

"languageOptions": {
  "parser": {
    "meta": {
      "name": "typescript-eslint/parser",
      "version": "7.0.2"
    }
  },
  "parserOptions": {
    "sourceType": "module"
  }
}

Additional Info

sourceType should be nested directly under languageOptions unless typescript-eslint has another option with the same name.

Versions

package	version
@typescript-eslint/eslint-plugin	7.0.2
@typescript-eslint/parser	7.0.2
typescript-eslint	7.0.2

[bradzacher]

The old style was to place it under parserOptions!
The reason this wasn't caught was because:

1. ParserOptions is declared as a loose object with an index signature to support all parsers.
2. our tooling really doesn't use that field at all because TS has its own inbuilt handling.