@antfu/eslint-config

• Auto fix for formatting (aimed to be used standalone without Prettier)
• Reasonable defaults, best practices, only one line of config
• Designed to work with TypeScript, JSX, Vue, JSON, YAML, Toml, Markdown, etc. Out-of-box.
• Opinionated, but very customizable
• ESLint Flat config, compose easily!
• Optional React, Next.js, Svelte, UnoCSS, Astro, Solid support
• Optional formatters support for formatting CSS, HTML, XML, etc.
• Style principle: Minimal for reading, stable for diff, consistent
  • Sorted imports, dangling commas
  • Single quotes, no semi
  • Using ESLint Stylistic
• Respects .gitignore by default
• Requires ESLint v9.5.0+

[!NOTE] Since v1.0.0, this config is rewritten to the new ESLint Flat config, check the release note for more details.

Since v3.0.0, ESLint v9.5.0+ is now required.

[!WARNING] I am super appreciative and even a bit flattered that so many of you are fond of using this config. For that reason, I tried to make it as flexible and customizable as possible to fit more use cases.

However, please keep in mind that this is still a personal config with a lot of opinions. Changes might not always work for everyone and every use case.

If you are using this config directly, I suggest you review the changes every time you update. Or if you want more control over the rules, always feel free to fork it. Thanks!

[!TIP] If you are interested in the tooling and the philosophy behind this config, I gave a talk about ESLint flat config at JSNation 2024 - ESLint One for All Made Easy, slides are here.

Usage

Starter Wizard

We provided a CLI tool to help you set up your project, or migrate from the legacy config to the new flat config with one command.

pnpm dlx @antfu/eslint-config@latest

Manual Install

If you prefer to set up manually:

pnpm i -D eslint @antfu/eslint-config

And create eslint.config.mjs in your project root:

// eslint.config.mjs
import antfu from '@antfu/eslint-config'

export default antfu()

// eslint.config.mjs
import antfu from '@antfu/eslint-config'
import { FlatCompat } from '@eslint/eslintrc'

const compat = new FlatCompat()

export default antfu(
  {
    ignores: [],
  },

  // Legacy config
  ...compat.config({
    extends: [
      'eslint:recommended',
      // Other extends...
    ],
  })

  // Other flat configs...
)

Add script for package.json

For example:

{
  "scripts": {
    "lint": "eslint",
    "lint:fix": "eslint --fix"
  }
}

IDE Support (auto fix on save)

{
  // Disable the default formatter, use eslint instead
  "prettier.enable": false,
  "editor.formatOnSave": false,

  // Auto fix
  "editor.codeActionsOnSave": {
    "source.fixAll.eslint": "explicit",
    "source.organizeImports": "never"
  },

  // Silent the stylistic rules in your IDE, but still auto fix them
  "eslint.rules.customizations": [
    { "rule": "style/*", "severity": "off", "fixable": true },
    { "rule": "format/*", "severity": "off", "fixable": true },
    { "rule": "*-indent", "severity": "off", "fixable": true },
    { "rule": "*-spacing", "severity": "off", "fixable": true },
    { "rule": "*-spaces", "severity": "off", "fixable": true },
    { "rule": "*-order", "severity": "off", "fixable": true },
    { "rule": "*-dangle", "severity": "off", "fixable": true },
    { "rule": "*-newline", "severity": "off", "fixable": true },
    { "rule": "*quotes", "severity": "off", "fixable": true },
    { "rule": "*semi", "severity": "off", "fixable": true }
  ],

  // Enable eslint for all supported languages
  "eslint.validate": [
    "javascript",
    "javascriptreact",
    "typescript",
    "typescriptreact",
    "vue",
    "html",
    "markdown",
    "json",
    "jsonc",
    "yaml",
    "toml",
    "xml",
    "gql",
    "graphql",
    "astro",
    "svelte",
    "css",
    "less",
    "scss",
    "pcss",
    "postcss"
  ]
}

local customizations = {
  { rule = 'style/*', severity = 'off', fixable = true },
  { rule = 'format/*', severity = 'off', fixable = true },
  { rule = '*-indent', severity = 'off', fixable = true },
  { rule = '*-spacing', severity = 'off', fixable = true },
  { rule = '*-spaces', severity = 'off', fixable = true },
  { rule = '*-order', severity = 'off', fixable = true },
  { rule = '*-dangle', severity = 'off', fixable = true },
  { rule = '*-newline', severity = 'off', fixable = true },
  { rule = '*quotes', severity = 'off', fixable = true },
  { rule = '*semi', severity = 'off', fixable = true },
}

local lspconfig = require('lspconfig')
-- Enable eslint for all supported languages
lspconfig.eslint.setup(
  {
    filetypes = {
      "javascript",
      "javascriptreact",
      "javascript.jsx",
      "typescript",
      "typescriptreact",
      "typescript.tsx",
      "vue",
      "html",
      "markdown",
      "json",
      "jsonc",
      "yaml",
      "toml",
      "xml",
      "gql",
      "graphql",
      "astro",
      "svelte",
      "css",
      "less",
      "scss",
      "pcss",
      "postcss"
    },
    settings = {
      -- Silent the stylistic rules in your IDE, but still auto fix them
      rulesCustomizations = customizations,
    },
  }
)

lspconfig.eslint.setup({
  --- ...
  on_attach = function(client, bufnr)
    vim.api.nvim_create_autocmd("BufWritePre", {
      buffer = bufnr,
      command = "EslintFixAll",
    })
  end,
})

Customization

Since v1.0, we migrated to ESLint Flat config. It provides much better organization and composition.

Normally you only need to import the antfu preset:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu()

And that's it! Or you can configure each integration individually, for example:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  // Type of the project. 'lib' for libraries, the default is 'app'
  type: 'lib',

  // `.eslintignore` is no longer supported in Flat config, use `ignores` instead
  // The `ignores` option in the option (first argument) is specifically treated to always be global ignores
  // And will **extend** the config's default ignores, not override them
  // You can also pass a function to modify the default ignores
  ignores: [
    '**/fixtures',
    // ...globs
  ],

  // Parse the `.gitignore` file to get the ignores, on by default
  gitignore: true,

  // Enable stylistic formatting rules
  stylistic: true,

  // Or customize the stylistic rules
  stylistic: {
    indent: 2, // 4, or 'tab'
    quotes: 'single', // or 'double'
  },

  // TypeScript and Vue are autodetected, you can also explicitly enable them:
  typescript: true,
  vue: true,

  // Disable jsonc and yaml support
  jsonc: false,
  yaml: false,
})

The antfu factory function also accepts any number of arbitrary custom config overrides:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu(
  {
    // Configures for antfu's config
  },

  // From the second arguments they are ESLint Flat Configs
  // you can have multiple configs
  {
    files: ['**/*.ts'],
    rules: {},
  },
  {
    rules: {},
  },
)

Going more advanced, you can also import fine-grained configs and compose them as you wish:

// eslint.config.js
import {
  combine,
  comments,
  ignores,
  imports,
  javascript,
  jsdoc,
  jsonc,
  markdown,
  node,
  sortPackageJson,
  sortTsconfig,
  stylistic,
  toml,
  typescript,
  unicorn,
  vue,
  yaml,
} from '@antfu/eslint-config'

export default combine(
  ignores(),
  javascript(/* Options */),
  comments(),
  node(),
  jsdoc(),
  imports(),
  unicorn(),
  typescript(/* Options */),
  stylistic(),
  vue(),
  jsonc(),
  yaml(),
  toml(),
  markdown(),
)

Check out the configs and factory for more details.

Thanks to sxzz/eslint-config for the inspiration and reference.

Plugins Renaming

Since flat config requires us to explicitly provide the plugin names (instead of the mandatory convention from npm package name), we renamed some plugins to make the overall scope more consistent and easier to write.

When you want to override rules, or disable them inline, you need to update to the new prefix:

-// eslint-disable-next-line @typescript-eslint/consistent-type-definitions
+// eslint-disable-next-line ts/consistent-type-definitions
type foo = { bar: 2 }

[!NOTE] About plugin renaming - it is actually rather a dangerous move that might lead to potential naming collisions, pointed out here and here. As this config also very personal and opinionated, I ambitiously position this config as the only "top-level" config per project, that might pivots the taste of how rules are named.

This config cares more about the user-facings DX, and try to ease out the implementation details. For example, users could keep using the semantic import/order without ever knowing the underlying plugin has migrated twice to eslint-plugin-i and then to eslint-plugin-import-x. User are also not forced to migrate to the implicit i/order halfway only because we swapped the implementation to a fork.

That said, it's probably still not a good idea. You might not want to do this if you are maintaining your own eslint config.

Feel free to open issues if you want to combine this config with some other config presets but faced naming collisions. I am happy to figure out a way to make them work. But at this moment I have no plan to revert the renaming.

Since v2.9.0, this preset will automatically rename the plugins also for your custom configs. You can use the original prefix to override the rules directly.

import antfu from '@antfu/eslint-config'

export default antfu()
  .renamePlugins({
    ts: '@typescript-eslint',
    yaml: 'yml',
    node: 'n'
    // ...
  })

Rules Overrides

Certain rules would only be enabled in specific files, for example, ts/* rules would only be enabled in .ts files and vue/* rules would only be enabled in .vue files. If you want to override the rules, you need to specify the file extension:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu(
  {
    vue: true,
    typescript: true
  },
  {
    // Remember to specify the file glob here, otherwise it might cause the vue plugin to handle non-vue files
    files: ['**/*.vue'],
    rules: {
      'vue/operator-linebreak': ['error', 'before'],
    },
  },
  {
    // Without `files`, they are general rules for all files
    rules: {
      'style/semi': ['error', 'never'],
    },
  }
)

We also provided the overrides options in each integration to make it easier:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  vue: {
    overrides: {
      'vue/operator-linebreak': ['error', 'before'],
    },
  },
  typescript: {
    overrides: {
      'ts/consistent-type-definitions': ['error', 'interface'],
    },
  },
  yaml: {
    overrides: {
      // ...
    },
  },
})

Config Composer

Since v2.10.0, the factory function antfu() returns a FlatConfigComposer object from eslint-flat-config-utils where you can chain the methods to compose the config even more flexibly.

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu()
  .prepend(
    // some configs before the main config
  )
  // overrides any named configs
  .override(
    'antfu/stylistic/rules',
    {
      rules: {
        'style/generator-star-spacing': ['error', { after: true, before: false }],
      }
    }
  )
  // rename plugin prefixes
  .renamePlugins({
    'old-prefix': 'new-prefix',
    // ...
  })
// ...

Vue

Vue support is detected automatically by checking if vue is installed in your project. You can also explicitly enable/disable it:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  vue: true
})

Vue 2

We have limited support for Vue 2 (as it's already reached EOL). If you are still using Vue 2, you can configure it manually by setting vueVersion to 2:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  vue: {
    vueVersion: 2
  },
})

As it's in maintenance mode, we only accept bug fixes for Vue 2. It might also be removed in the future when eslint-plugin-vue drops support for Vue 2. We recommend upgrading to Vue 3 if possible.

Vue Accessibility

To enable Vue accessibility support, you need to explicitly turn it on:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  vue: {
    a11y: true
  },
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-vuejs-accessibility

Optional Configs

We provide some optional configs for specific use cases, that we don't include their dependencies by default.

Formatters

Use external formatters to format files that ESLint cannot handle yet (.css, .html, etc). Powered by eslint-plugin-format.

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  formatters: {
    /**
     * Format CSS, LESS, SCSS files, also the `<style>` blocks in Vue
     * By default uses Prettier
     */
    css: true,
    /**
     * Format HTML files
     * By default uses Prettier
     */
    html: true,
    /**
     * Format Markdown files
     * Supports Prettier and dprint
     * By default uses Prettier
     */
    markdown: 'prettier'
  }
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-format

React

To enable React support, you need to explicitly turn it on:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  react: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D @eslint-react/eslint-plugin eslint-plugin-react-hooks eslint-plugin-react-refresh

Next.js

To enable Next.js support, you need to explicitly turn it on:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  nextjs: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D @next/eslint-plugin-next

Svelte

To enable svelte support, you need to explicitly turn it on:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  svelte: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-svelte

Astro

To enable astro support, you need to explicitly turn it on:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  astro: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-astro

Solid

To enable Solid support, you need to explicitly turn it on:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  solid: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D eslint-plugin-solid

UnoCSS

To enable UnoCSS support, you need to explicitly turn it on:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  unocss: true,
})

Running npx eslint should prompt you to install the required dependencies, otherwise, you can install them manually:

npm i -D @unocss/eslint-plugin

Optional Rules

This config also provides some optional plugins/rules for extended usage.

command

Powered by eslint-plugin-command. It is not a typical rule for linting, but an on-demand micro-codemod tool that triggers by specific comments.

For a few triggers, for example:

• /// to-function - converts an arrow function to a normal function
• /// to-arrow - converts a normal function to an arrow function
• /// to-for-each - converts a for-in/for-of loop to .forEach()
• /// to-for-of - converts a .forEach() to a for-of loop
• /// keep-sorted - sorts an object/array/interface
• ... etc. - refer to the documentation

You can add the trigger comment one line above the code you want to transform, for example (note the triple slash):

/// to-function
const foo = async (msg: string): void => {
  console.log(msg)
}

Will be transformed to this when you hit save with your editor or run eslint --fix:

async function foo(msg: string): void {
  console.log(msg)
}

The command comments are usually one-off and will be removed along with the transformation.

Type Aware Rules

You can optionally enable the type aware rules by passing the options object to the typescript config:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  typescript: {
    tsconfigPath: 'tsconfig.json',
  },
})

Editor Specific Disables

Auto-fixing for the following rules are disabled when ESLint is running in a code editor:

• prefer-const
• test/no-only-tests
• unused-imports/no-unused-imports
• pnpm/json-enforce-catalog
• pnpm/json-prefer-workspace-settings
• pnpm/json-valid-catalog

Since v3.16.0, they are no longer disabled, but made non-fixable using this helper.

This is to prevent unused imports from getting removed by the editor during refactoring to get a better developer experience. Those rules will be applied when you run ESLint in the terminal or Lint Staged. If you don't want this behavior, you can disable them:

// eslint.config.js
import antfu from '@antfu/eslint-config'

export default antfu({
  isInEditor: false
})

Lint Staged

If you want to apply lint and auto-fix before every commit, you can add the following to your package.json:

{
  "simple-git-hooks": {
    "pre-commit": "pnpm lint-staged"
  },
  "lint-staged": {
    "*": "eslint --fix"
  }
}

and then

npm i -D lint-staged simple-git-hooks

// to active the hooks
npx simple-git-hooks

View what rules are enabled

I built a visual tool to help you view what rules are enabled in your project and apply them to what files, @eslint/config-inspector

Go to your project root that contains eslint.config.js and run:

npx @eslint/config-inspector

Versioning Policy

This project follows Semantic Versioning for releases. However, since this is just a config and involves opinions and many moving parts, we don't treat rules changes as breaking changes.

Changes Considered as Breaking Changes

• Node.js version requirement changes
• Huge refactors that might break the config
• Plugins made major changes that might break the config
• Changes that might affect most of the codebases

Changes Considered as Non-breaking Changes

• Enable/disable rules and plugins (that might become stricter)
• Rules options changes
• Version bumps of dependencies

Badge

If you enjoy this code style, and would like to mention it in your project, here is the badge you can use:

[![code style](https://antfu.me/badge-code-style.svg)](https://github.com/antfu/eslint-config)

FAQ

Prettier?

Why I don't use Prettier

Well, you can still use Prettier to format files that are not supported well by ESLint yet, such as .css, .html, etc. See formatters for more details.

dprint?

dprint is also a great formatter that with more abilities to customize. However, it's in the same model as Prettier which reads the AST and reprints the code from scratch. This means it's similar to Prettier, which ignores the original line breaks and might also cause the inconsistent diff. So in general, we prefer to use ESLint to format and lint JavaScript/TypeScript code.

Meanwhile, we do have dprint integrations for formatting other files such as .md. See formatters for more details.

How to format CSS?

You can opt-in to the formatters feature to format your CSS. Note that it's only doing formatting, but not linting. If you want proper linting support, give stylelint a try.

Top-level Function Style, etc.

I am a very opinionated person, so as this config. I prefer the top-level functions always using the function declaration over arrow functions; I prefer one-line if statements without braces and always wraps, and so on. I even wrote some custom rules to enforce them.

I know they are not necessarily the popular opinions. If you really want to get rid of them, you can disable them with:

import antfu from '@antfu/eslint-config'

export default antfu({
  lessOpinionated: true
})

I prefer XXX...

Sure, you can configure and override rules locally in your project to fit your needs. If that still does not work for you, you can always fork this repo and maintain your own.

Check Also

• antfu/dotfiles - My dotfiles
• antfu/vscode-settings - My VS Code settings
• antfu/starter-ts - My starter template for TypeScript library
• antfu/vitesse - My starter template for Vue & Vite app

License

MIT License © 2019-PRESENT Anthony Fu