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@jdpnielsen/eslint-flat-config

  • Single quotes, semi & tab indentation
  • Auto fix for formatting (aimed to be used standalone without Prettier)
  • Designed to work with TypeScript, React JSX & next.js out-of-box
  • Lints also for json, yaml, markdown
  • Sorted imports, dangling commas
  • Reasonable defaults, best practices, only one-line of config
  • Respects .gitignore by default
  • ESLint Flat config, compose easily!
  • Using ESLint Stylistic
  • Style principle: Minimal for reading, stable for diff, consistent

Usage

Install

pnpm i -D eslint @jdpnielsen/eslint-flat-config

Create config file

With "type": "module" in package.json (recommended):

// eslint.config.js
import setupConfig from '@jdpnielsen/eslint-flat-config';

export default setupConfig();

With CJS:

// eslint.config.js
const setupConfig = require('@jdpnielsen/eslint-flat-config').default;

module.exports = setupConfig();

Note that .eslintignore no longer works in Flat config, see customization for more details.

Add script for package.json

For example:

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

VS Code support (auto fix)

Install VS Code ESLint extension

Add the following settings to your .vscode/settings.json:

{
	// Enable the ESlint flat config support
	"eslint.experimental.useFlatConfig": true,

	// 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 you IDE, but still auto fix them
	"eslint.rules.customizations": [
		{ "rule": "style/*", "severity": "off" },
		{ "rule": "*-indent", "severity": "off" },
		{ "rule": "*-spacing", "severity": "off" },
		{ "rule": "*-spaces", "severity": "off" },
		{ "rule": "*-order", "severity": "off" },
		{ "rule": "*-dangle", "severity": "off" },
		{ "rule": "*-newline", "severity": "off" },
		{ "rule": "*quotes", "severity": "off" },
		{ "rule": "*semi", "severity": "off" }
	],

	// Enable eslint for all supported languages
	"eslint.validate": [
		"javascript",
		"javascriptreact",
		"typescript",
		"typescriptreact",
		"vue",
		"html",
		"markdown",
		"json",
		"jsonc",
		"yaml"
	]
}

Customization

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

Normally you only need to import the preset:

// eslint.config.js
import setupConfig from '@jdpnielsen/eslint-flat-config';

export default setupConfig();

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

// eslint.config.js
import setupConfig from '@jdpnielsen/eslint-flat-config';

export default setupConfig({
	// Enable stylistic formatting rules
	// stylistic: true,

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

	// TypeScript, React, Nextjs and Vue are auto-detected, you can also explicitly enable them:
	typescript: true,
	react: true,
	next: true,
	vue: true,

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

	// `.eslintignore` is no longer supported in Flat config, use `ignores` instead
	ignores: [
		'./fixtures',
		// ...globs
	]
});

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

// eslint.config.js
import setupConfig from '@jdpnielsen/eslint-flat-config';

export default setupConfig(
	{
		// Configures for factory function
	},

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

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

Plugins Renaming

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

New Prefix Original Prefix Source Plugin
import/* i/* eslint-plugin-i
node/* n/* eslint-plugin-n
yaml/* yml/* eslint-plugin-yml
ts/* @typescript-eslint/* @typescript-eslint/eslint-plugin
style/* @stylistic/* @stylistic/eslint-plugin
test/* vitest/* eslint-plugin-vitest
test/* no-only-tests/* eslint-plugin-no-only-tests

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 }

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 setupConfig from '@jdpnielsen/eslint-flat-config';

export default setupConfig(
	{ 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 an overrides options to make it easier:

// eslint.config.js
import setupConfig from '@jdpnielsen/eslint-flat-config';

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

Optional Rules

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

perfectionist (sorting)

This plugin eslint-plugin-perfectionist allows you to sorted object keys, imports, etc, with auto-fix.

The plugin is installed but no rules are enabled by default.

It's recommended to opt-in on each file individually using configuration comments.

/* eslint perfectionist/sort-objects: "error" */
const objectWantedToSort = {
	a: 2,
	b: 1,
	c: 3,
};
/* eslint perfectionist/sort-objects: "off" */

Type Aware Rules

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

// eslint.config.js
import setupConfig from '@jdpnielsen/eslint-flat-config';

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

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

Versioning Policy

This project follows Semantic Versioning for releases. However, since this is just a config and involved with 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

License

MIT License © 2023 Joshua Nielsen