Lint failure: TypeError: Plugin config "mixed-esm-and-cjs" not found in plugin "n".

[MikeMcC399]

Current behavior

When yo eslint:plugin is used to generate a new plugin, running the script lint:js fails with

TypeError: Plugin config "mixed-esm-and-cjs" not found in plugin "n".

This is a regression introduced in generator-eslint@5.2.0. The release generator-eslint@5.1.3 does not have this issue.

Expected behavior

When yo eslint:plugin is used to generate a new plugin, running the script lint:js should succeed out-of-the-box.

Versions

Component	Version
Ubuntu	24.04.3 LTS
Node.js	v22.20.0 LTS
npm	10.9.3
yo	5.1.0
generator-eslint	5.2.1
eslint	9.37.0
eslint-plugin-n	17.23.1
eslint-plugin-eslint-plugin	6.5.0

Steps to reproduce

npm install yo@latest -g
npm install generator-eslint@latest -g

cd $(mktemp -d)
yo eslint:plugin

and accept defaults:

$ yo eslint:plugin
? What is your name? Tester
? What is the plugin ID? template-test
? Type a short description of this plugin: Template test
? Does this plugin contain custom ESLint rules? Yes
? Does this plugin contain one or more processors? No
   create package.json
   create eslint.config.mjs
   create lib/index.js
   create README.md

Changes to package.json were detected.
Error detecting the package manager. Falling back to npm.

Running npm install for you to install the required dependencies.

added 242 packages, and audited 243 packages in 16s

70 packages are looking for funding
  run `npm fund` for details

found 0 vulnerabilities

Then execute linting:

npm run lint:js

Logs

$ npm run lint:js

> eslint-plugin-template-test@0.0.0 lint:js
> eslint .


Oops! Something went wrong! :(

ESLint: 9.37.0

TypeError: Plugin config "mixed-esm-and-cjs" not found in plugin "n".
    at findPluginConfig (/tmp/tmp.6CcU4BUgW5/node_modules/@eslint/config-helpers/dist/cjs/index.cjs:287:8)
    at /tmp/tmp.6CcU4BUgW5/node_modules/@eslint/config-helpers/dist/cjs/index.cjs:423:25
    at Array.map (<anonymous>)
    at processExtends (/tmp/tmp.6CcU4BUgW5/node_modules/@eslint/config-helpers/dist/cjs/index.cjs:421:36)
    at /tmp/tmp.6CcU4BUgW5/node_modules/@eslint/config-helpers/dist/cjs/index.cjs:497:38
    at Array.flatMap (<anonymous>)
    at processConfigList (/tmp/tmp.6CcU4BUgW5/node_modules/@eslint/config-helpers/dist/cjs/index.cjs:497:20)
    at defineConfig (/tmp/tmp.6CcU4BUgW5/node_modules/@eslint/config-helpers/dist/cjs/index.cjs:533:9)
    at file:///tmp/tmp.6CcU4BUgW5/eslint.config.mjs?mtime=1759647699530:6:16
    at ModuleJob.run (node:internal/modules/esm/module_job:345:25)

Other

The failing configuration is for eslint-plugin-n

See template plugin/templates/_eslint.config.mjs

[aladdin-add]

it was introduced in 0ff5d1f.

generator-eslint/plugin/templates/_eslint.config.mjs

Line 19 in 6db0c9a

extends: ["n/mixed-esm-and-cjs"],

✅n/flat/mixed-esm-and-cjs
❌n/mixed-esm-and-cjs

seems it's a bug in config-helper if the eslintrc config does not exisit.

[eslint-github-bot]

👋 Hi! This issue is being addressed in pull request #228. Thanks, @aladdin-add!