PR Checklist

• Addresses an existing open issue:fixesEnhancement: support ESLint's newdefineConfig string config references #10934
• That issue was marked asaccepting prs
• Steps inContributing were taken

Overview

Previously,

• eslintrc configs were stored atpackages/eslint-plugin/src/configs, and were exposed via theplugin.configs field
• flat configs were stored atpackages/typescript-eslint/src/configs, and were exposed via thetseslint.configs field.
• a typescript-eslint parserobject was created in the typescript-eslint package, is used inside the flat configs, and was exposed viatseslint.parser.
• eslintrc configs are stringly typed, so there was no need for exporting configs or parser objects from eslint-plugin (only "exception" was a littleuse-at-your-own-risk config generation function - this was just to share code, not for any runtime reason).

Now,

• eslintrc configs are stored atpackages/eslint-plugin/src/configs/eslintrc.
• flat configs are stored atpackages/eslint-plugin/src/configs/flat.
• Theplugin.configs object contains all the same eslintrc configsand all the flat configs, prefixed with'flat/. Conceptually,

  constplugin={configs:{strict:eslintrcStrict,'flat/strict':flatStrict,// likewise for the rest of the configs...}// rest of the plugin fields...};

  Only the eslintrc configs are acknowledged in the publicly exported types. Therefore, this will be invisible to users in the editor.
• thetseslint.configsdoes not use theflat/ prefixes. Itonly exports eslint v9 flat configs, just like it always has.
• Because the flat configs need a parser object, the eslint-plugin package now creates the parser object.
• In order for relevant objects ineslint-plugin to be=== to their counterparts intypescript-eslint at runtime, theflatConfigs andparser are now exported fromeslint-plugin via a newuse-at-your-own-risk export in order to be re-exported bytypescript-eslint.

In summary, these changes ensure:

constassert=require('node:assert');const{ defineConfig}=require('eslint/config');consttseslint=require('typescript-eslint');consttseslintPlugin=require('@typescript-eslint/eslint-plugin');assert(tseslint.plugin===tseslintPlugin);assert(tseslint.configs.strict===tseslintPlugin.configs['flat/strict']);assert(tseslint.parser===tseslintPlugin.configs['flat/strict'][0].parser);// doesn't throwdefineConfig({extends:['tseslint/strict'],plugins:{tseslint:tseslintPlugin},});// BUTassert(tseslint.configs!==tseslintPlugin.configs);