ESLint doesn't work with flat config

[TiroZit]

Describe the bug

ESLint introduced a new configuration format eslint.config.js (flat config). With the new format, an error is thrown when starting the application:

node:internal/event_target:1012
  process.nextTick(() => { throw err; });
                           ^
Error: No ESLint configuration found in \src\stories\_utils\docs.
    at CascadingConfigArrayFactory._finalizeConfigArray (\node_modules\@eslint\eslintrc\dist\eslintrc.cjs:3977:19)
    at CascadingConfigArrayFactory.getConfigArrayForFile (\node_modules\@eslint\eslintrc\dist\eslintrc.cjs:3768:21)
    at FileEnumerator._iterateFilesRecursive (\node_modules\eslint\lib\cli-engine\file-enumerator.js:473:52)
    at _iterateFilesRecursive.next (<anonymous>)
    at FileEnumerator._iterateFilesRecursive (\node_modules\eslint\lib\cli-engine\file-enumerator.js:495:33)
    at _iterateFilesRecursive.next (<anonymous>)
    at FileEnumerator._iterateFilesRecursive (\node_modules\eslint\lib\cli-engine\file-enumerator.js:495:33)
    at _iterateFilesRecursive.next (<anonymous>)
    at FileEnumerator._iterateFilesRecursive (\node_modules\eslint\lib\cli-engine\file-enumerator.js:495:33)
    at _iterateFilesRecursive.next (<anonymous>)
Emitted 'error' event on Worker instance at:
    at [kOnErrorMessage] (node:internal/worker:300:10)
    at [kOnMessage] (node:internal/worker:311:37)
    at MessagePort.<anonymous> (node:internal/worker:212:57)
    at [nodejs.internal.kHybridDispatch] (node:internal/event_target:737:20)
    at exports.emitMessage (node:internal/per_context/messageport:23:28)
    at [kOnExit] (node:internal/worker:278:5)
    at Worker.<computed>.onexit (node:internal/worker:209:20) {
  messageTemplate: 'no-config-found',
  messageData: {
    directoryPath: 'src\\stories\\_utils\\docs'
  }

Running ESLint directly via CLI works with the new config. The checker plugin worked properly before migrating to the new ESLint config.

Expected behavior

ESLint should run without an error and the eslint.config.js file should be used.

The ESLint class used by this plugin doesn't support the new flat config. For the flat config the FlatESLint class must be used which is only exported via eslint/use-at-your-own-risk entrypoint: https://eslint.org/blog/2022/08/new-config-system-part-3/#using-flat-config-with-the-eslint-class

[olmokramer]

I was able to work around this issue by changing node_modules/@rollup/plugin-eslint/dist/es/index.js to use the FlatESLint class:

--- node_modules/@rollup/plugin-eslint/dist/es/index.js.bak     2023-12-20 19:51:17.176681875 +0100
+++ node_modules/@rollup/plugin-eslint/dist/es/index.js 2023-12-20 19:51:40.537216607 +0100
@@ -1,6 +1,7 @@
 import { resolve, relative, sep } from 'path';
 import { createFilter } from '@rollup/pluginutils';
-import { ESLint } from 'eslint';
+import eslintPkg from 'eslint/use-at-your-own-risk';
+const { FlatESLint: ESLint } = eslintPkg;

 function normalizePath(id) {
     return relative(process.cwd(), id).split(sep).join('/');

[timotheus90]

Looks like an easy fix