fix: eslint config error when using defineConfig

[aladdin-add]

Prerequisites checklist

• I have read the contributing guidelines.

What is the purpose of this pull request?

when running npx eslint ., it output the errors:

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)

Oops! Something went wrong! :(

ESLint: 9.37.0


A config object has a "plugins" key defined as an array of strings. It looks something like this:

    {
        "plugins": ["eslint-plugin"]
    }

Flat config requires "plugins" to be an object, like this:

    {
        plugins: {
            eslint-plugin: pluginObject
        }
    }

Please see the following page for information on how to convert your config object into the correct format:
https://eslint.org/docs/latest/use/configure/migration-guide#importing-plugins-and-custom-parsers

If you're using a shareable config that you cannot rewrite in flat config format, then use the compatibility utility:
https://eslint.org/docs/latest/use/configure/migration-guide#using-eslintrc-configs-in-flat-config

fixes #227

What changes did you make? (Give an overview)

• use the flat config directly, instead of guessing the config format.

Related Issues

Is there anything you'd like reviewers to focus on?

const config = {plugins: ["eslint-plugin"]};

this is wrongly seen as flat config; we might need to fix it in @eslint/config-helper.

[MikeMcC399]

@aladdin-add

Using the changed config

import { defineConfig } from "eslint/config";
import pluginJs from "@eslint/js";
import pluginNode from "eslint-plugin-n";
import eslintPlugin from "eslint-plugin-eslint-plugin";

export default defineConfig([
    {
        name: "eslint/js",
        plugins: {
            js: pluginJs,
        },
        extends: ["js/recommended"],
    },
    {
        name: "eslint/node",
        plugins: {
            n: pluginNode,
        },
        extends: ["n/flat/mixed-esm-and-cjs"],
    },
    {
        name: "eslint/eslint-plugin",
        plugins: {
            "eslint-plugin": eslintPlugin,
        },
        extends: ["eslint-plugin/recommended"],
    }
]);

I'm getting a different error message from npm run lint:js:

$ npm run lint:js

> eslint-plugin-t@0.0.0 lint:js
> eslint .


Oops! Something went wrong! :(

ESLint: 9.37.0


A config object has a "plugins" key defined as an array of strings. It looks something like this:

    {
        "plugins": ["eslint-plugin"]
    }

Flat config requires "plugins" to be an object, like this:

    {
        plugins: {
            eslint-plugin: pluginObject
        }
    }

Please see the following page for information on how to convert your config object into the correct format:
https://eslint.org/docs/latest/use/configure/migration-guide#importing-plugins-and-custom-parsers

If you're using a shareable config that you cannot rewrite in flat config format, then use the compatibility utility:
https://eslint.org/docs/latest/use/configure/migration-guide#using-eslintrc-configs-in-flat-config

Do you see this as well, or is it working for you?

[aladdin-add]

Yes, I noticed that, too. I will investigate.

[aladdin-add]

1. upgrading eslint-plugin-eslint-pluginv7.
2. use the prefixed config extends: ["eslint-plugin/flat/recommended"].

Both can solve the issue. 😂

[MikeMcC399]

@aladdin-add

Thanks for your actions! 👍🏻 This was much more complicated than I could understand and fix on my own!

[MikeMcC399]

I successfully ran https://github.com/eslint/generator-eslint/blob/aladdin-add-patch-2/plugin/templates/_eslint.config.mjs locally with npm run lint:js, so that looks good to go!

Thank you very much!

[mdjermanovic]

Is this change necessary if eslint/rewrite#288 is accepted?

[aladdin-add]

yes, it's necessary, that pr is only fixing the eslint-plugin-n issue.

[aladdin-add]

the cause is defineConfig() simply check whether the property exists rather than determining its type to verify if it conforms to the eslintrc format:
https://github.com/eslint/rewrite/blob/4334e769be7cfe5b515d64058176571aab18ea5c/packages/config-helpers/src/define-config.js#L76-L84

const config = {plugins: ["eslint-plugin"]};

the config will be treated as flat config, while actually it's eslintrc format.

[mdjermanovic]

Ah, I see, both config formats have a plugins property, but of different type. Maybe that could be another improvement in addition to eslint/rewrite#288. Either way, since there are multiple issues, I agree with this fix (even if it's temporary) in generator-eslint.

[lumirlumir]

LGTM, thanks!

Would like @mdjermanovic to verify before merging.

[mdjermanovic]

LGTM, thanks!