Provide support for eslint 9's flat configuration

[ajmas]

It is not clear whether vue-eslint-parser supports eslint 9's flat configuration, but the current issue I am running into suggest that flat configuration may not be supported.

I currently have the following eslint.config.js:

import importPlugin from 'eslint-plugin-import';
import vueParser from 'vue-eslint-parser';
import tsParser from '@typescript-eslint/parser';
import tsPlugin from '@typescript-eslint/eslint-plugin';
import { FlatCompat } from '@eslint/eslintrc';
import path from 'path';
import { fileURLToPath } from 'url';

// mimic CommonJS variables -- not needed if using CommonJS
const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

const compat = new FlatCompat({
  baseDirectory: __dirname
});

export default [
  ...compat.extends('plugin:vue/vue3-recommended'),
  {
    files: [
      '**/*.vue', '**/*.js', '**/*.jsx', '**/*.cjs', 
      '**/*.mjs', '**/*.ts', '**/*.tsx', '**/*.cts', 
      '**/*.mts'
   ],
    ignores: ['.gitignore'],
    plugins: {
      import: importPlugin,
      '@typescript-eslint': tsPlugin
    },
    languageOptions: {
      parser: vueParser,
      parserOptions: {
        parser: tsParser
      },
      ecmaVersion: 'latest',
    },
    rules: {
      // allow async-await
      'generator-star-spacing': 'off',
      // allow paren-less arrow functions
      'arrow-parens': 'off',
      'one-var': 'off',
      'no-void': 'off',
      'multiline-ternary': 'off',

      'import/first': 'off',
      'import/namespace': 'error',
      'import/default': 'error',
      'import/export': 'error',
      'import/extensions': 'off',
      'import/no-unresolved': 'off',
      'import/no-extraneous-dependencies': 'off',
      'prefer-promise-reject-errors': 'off',
      'space-before-function-paren': 'error',
      semi: [2, 'always'],
      indent: ['error', 2],
      'vue/multi-word-component-names': 'warn',

      // TypeScript
      quotes: ['warn', 'single', { avoidEscape: true }],
      '@typescript-eslint/explicit-function-return-type': 'off',
      '@typescript-eslint/explicit-module-boundary-types': 'off',
      '@typescript-eslint/no-unnecessary-type-assertion': 'off',
      '@typescript-eslint/no-unsafe-assignment': 'off',
      '@typescript-eslint/no-unsafe-member-access': 'off',
      '@typescript-eslint/no-unsafe-call': 'off',
      '@typescript-eslint/no-explicit-any': 'off',
      '@typescript-eslint/restrict-template-expressions': 'off',
      '@typescript-eslint/no-misused-promises': 'off',
      '@typescript-eslint/no-unsafe-argument': 'off',

      'vue/singleline-html-element-content-newline': 'off',
      'vue/max-attributes-per-line': 'off',

      // allow debugger during development only
      'no-debugger': process.env.NODE_ENV === 'production' ? 'error' : 'off'
    }
  }
];

This is currently giving me errors of the type:

35:38 error Parse errors in imported module 'vue': parserPath or languageOptions.parser is required! (undefined:undefined) import/namespace 36:31 error Parse errors in imported module 'vue': parserPath or languageOptions.parser is required! (undefined:undefined) imp

Related dependencies:

    "@vue/cli-service": "~5.0.8",
    "@vue/eslint-config-prettier": "^9.0.0",
    "@vue/eslint-config-typescript": "^13.0.0",
    "@vue/tsconfig": "^0.5.1",
    "eslint": "^9.2.0",
    "eslint-config-standard": "^17.0.0",
    "eslint-plugin-import": "^2.27.5",
    "eslint-plugin-n": "^17.4.0",
    "eslint-plugin-promise": "^6.1.1",
    "eslint-plugin-vue": "^9.10.0",

[abdul-alhasany]

You are using eslint-plugin-import which does not support flat config yet. That could be the issue.

[ajmas]

Thanks. I’ll explore this as a possibility. Short term I’ve downgraded back to eslint 8.

[KyleBrown-804]

It looks like this doesn't support eslint 9 yet, I see "eslint": "^8.12.0" in the package.json as of now.

[jynxioxiao-lb]

Its releases' changelog doesn't include any content related to ESLint 9, so...

[ratherblue]

Bumping this, does anyone know what needs to be fixed to get ESLint support? Happy to help contribute as it's blocking our team's ability to upgrade to ESLint 9

[dclause]

@ratherblue: I currently have vue3 + typescript + eslint9, not using vue-eslint-parser though, but I wonder why it is actually needed here. Not sure it helps your case, but here it is:

In package.json (extract only):

"@eslint/js": "^9.8.0",
"@types/eslint__js": "^8.42.3",
"@vue/tsconfig": "^0.5.1",
"eslint": "^9.8.0",
"eslint-plugin-promise": "^7.0.0",
"eslint-plugin-simple-import-sort": "^12.1.1",
"eslint-plugin-vue": "^9.27.0",
"typescript": "~5.5.4",
"typescript-eslint": "^8.0.0",

Here is my eslint.config.js :

import js from '@eslint/js';
import pluginPromise from 'eslint-plugin-promise';
import simpleImportSort from 'eslint-plugin-simple-import-sort';
import vue from 'eslint-plugin-vue';
import ts from 'typescript-eslint';

export default [
  {
    languageOptions: {
      ecmaVersion: 'latest',
    },
  },

  // js
  js.configs.recommended,

  // ts
  ...ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/no-explicit-any': 'warn',
      '@typescript-eslint/no-unused-expressions': ['error', { allowTernary: true }],
    },
  },

  // vue
  ...vue.configs['flat/recommended'],
  {
    // files: ['*.vue', '**/*.vue'],
    languageOptions: {
      parserOptions: {
        parser: ts.parser,
      },
    },
  },
  {
    rules: {
      'vue/multi-word-component-names': 'off',
      'vue/no-unused-vars': ['error', { ignorePattern: '^_' }],
      'vue/max-attributes-per-line': ['error', { singleline: 5 }],
    },
  },

  // Sort imports
  {
    plugins: {
      'simple-import-sort': simpleImportSort,
    },
    rules: {
      'simple-import-sort/imports': [
        'error',
        {
          groups: [
            [
              '^\\u0000', // all side effects (0 at start)
              '^[^/\\.].*\u0000$', // external types (0 at end)
              '^\\..*\u0000$', // internal types (0 at end)
              '^@?\\w', // Starts with @
              '^[^.]', // any
              '^\\.', // local
            ],
          ],
        },
      ],
      'simple-import-sort/exports': 'error',
    },
  },

  // Promise
  pluginPromise.configs['flat/recommended'],
];

[sid-6581]

@dclause can you try it with type information enabled for typescript-eslint? That's not working for me.

[dclause]

@sid-6581 Not sure what you ask here: You can change my previous example as such :

// ts
// ...ts.configs.recommended,
...ts.configs.recommendedTypeChecked,
{
  files: ['**/*.ts', '**/*.tsx', '**/*.cts', '**/*.mts'],
  languageOptions: {
    parserOptions: {
      project: true,
      tsconfigRootDir: import.meta.dirname,
      parser: ts.parser,
      extraFileExtensions: ['.vue'],
    },
  },
  rules: {
    '@typescript-eslint/no-explicit-any': 'warn',
    '@typescript-eslint/no-unused-expressions': ['error', { allowTernary: true }],
  },
},

[sid-6581]

@dclause Thanks! I was able to get it to work eventually, it was a little more complicated by the fact that I'm using pug and I have a monorepo. Here is what I ended up with:

import js from "@eslint/js";
import ts from "typescript-eslint";
import vue from "eslint-plugin-vue";
import vuePug from "eslint-plugin-vue-pug";
import vueParser from "vue-eslint-parser";
import stylistic from "@stylistic/eslint-plugin";

export default ts.config(
  {
    files: ["**/*.js", "**/*.ts", "**/*.vue"],
  },

  {
    ignores: ["**/dist/*", "**/wwwroot/*", "**/api.ts", "**/bin/*", "**/obj/*"],
  },

  js.configs.recommended,
  stylistic.configs["recommended-flat"],
  ...ts.configs.strictTypeChecked,
  ...ts.configs.stylisticTypeChecked,
  ...vue.configs["flat/recommended"],
  stylistic.configs["disable-legacy"],

  {
    languageOptions: {
      parser: vueParser,
      parserOptions: {
        ecmaVersion: "latest",
        extraFileExtensions: [".vue"],
        parser: ts.parser,
        project: ["./tsconfig.json", "./src/FrontEnd.Shared/tsconfig.json"],
        sourceType: "module",
        templateTokenizer: {
          pug: "vue-eslint-parser-template-tokenizer-pug",
        },
        tsconfigRootDir: import.meta.dirname,
      },
    },

    plugins: {
      "vue-pug": vuePug,
    },

   rules: { ... }
}

[justingrant]

Some related info that may be helpful: apparently typescript-eslint only supports one set of tsconfig settings per project file. It's a singleton per project file. See https://github.com/typescript-eslint/typescript-eslint/issues/6778 and https://github.com/sveltejs/eslint-plugin-svelte/issues/422.

For configs that apply different rules to different sets of files, I'm not sure how to get ESLint to work, where "work" means that I'm getting ESLint errors output for .vue files.

Also I'm using Vue 2, if that matters.

I've tried to create a bunch of separate tsconfig files to trick ESLint into linting .vue files, but so far this hasn't worked.

If anyone does have a config that successfully lints .vue files (especially if you can use different rules for different files), then it'd be great to see that config!