@eslint/eslintrc

What is @eslint/eslintrc?

The @eslint/eslintrc package is a utility for working with ESLint configuration files. It provides tools to load and parse ESLint configuration files, resolve extends chains, and manage configuration cascading and hierarchy.

What are @eslint/eslintrc's main functionalities?

Loading ESLint Configuration

This feature allows you to load an ESLint configuration file using the ConfigArrayFactory class. The loaded configuration can then be used to configure the ESLint engine.

const { ConfigArrayFactory } = require('@eslint/eslintrc');
const factory = new ConfigArrayFactory();
const configArray = factory.loadFile('.eslintrc.js');

Parsing Configuration Files

This feature is used to parse ESLint configuration files directly. It is part of the legacy API and allows for direct interaction with configuration files.

const { Legacy: { ConfigFile } } = require('@eslint/eslintrc');
const config = ConfigFile.load('.eslintrc');

Resolving Extends Chains

This feature resolves the 'extends' chains in ESLint configuration files, allowing you to get the final configuration that applies to a specific file, taking into account all the extended configurations.

const { CascadingConfigArrayFactory } = require('@eslint/eslintrc');
const factory = new CascadingConfigArrayFactory();
const configArray = factory.getConfigArrayForFile('some-file.js');

Other packages similar to @eslint/eslintrc

eslint

The 'eslint' package is the core linting library that provides the primary functionality for linting JavaScript code. It includes the ability to load and interpret configuration files, which @eslint/eslintrc also does, but as a separate utility focused on configuration management.

eslint-config-prettier

The 'eslint-config-prettier' package is an ESLint configuration that disables rules that might conflict with Prettier. While it does not provide utilities for managing configurations, it is an example of a package that extends ESLint's configuration capabilities.

eslint-plugin-import

The 'eslint-plugin-import' package is a plugin that provides linting rules related to ES6+ import/export syntax. It extends ESLint's functionality with additional rules, similar to how @eslint/eslintrc extends configuration management capabilities.

README

ESLintRC Library

This repository contains the legacy ESLintRC configuration file format for ESLint. This package is not intended for use outside of the ESLint ecosystem. It is ESLint-specific and not intended for use in other programs.

Note: This package is frozen except for critical bug fixes as ESLint moves to a new config system.

Installation

You can install the package as follows:

npm install @eslint/eslintrc --save-dev

# or

yarn add @eslint/eslintrc -D

Usage (ESM)

The primary class in this package is FlatCompat, which is a utility to translate ESLintRC-style configs into flat configs. Here's how you use it inside of your eslint.config.js file:

import { FlatCompat } from "@eslint/eslintrc";
import js from "@eslint/js";
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,                  // optional; default: process.cwd()
    resolvePluginsRelativeTo: __dirname,       // optional
    recommendedConfig: js.configs.recommended, // optional unless you're using "eslint:recommended"
    allConfig: js.configs.all,                 // optional unless you're using "eslint:all"
});

export default [

    // mimic ESLintRC-style extends
    ...compat.extends("standard", "example", "plugin:react/recommended"),

    // mimic environments
    ...compat.env({
        es2020: true,
        node: true
    }),

    // mimic plugins
    ...compat.plugins("jsx-a11y", "react"),

    // translate an entire config
    ...compat.config({
        plugins: ["jsx-a11y", "react"],
        extends: "standard",
        env: {
            es2020: true,
            node: true
        },
        rules: {
            semi: "error"
        }
    })
];

Usage (CommonJS)

Using FlatCompat in CommonJS files is similar to ESM, but you'll use require() and module.exports instead of import and export. Here's how you use it inside of your eslint.config.js CommonJS file:

const { FlatCompat } = require("@eslint/eslintrc");
const js = require("@eslint/js");

const compat = new FlatCompat({
    baseDirectory: __dirname,                  // optional; default: process.cwd()
    resolvePluginsRelativeTo: __dirname,       // optional
    recommendedConfig: js.configs.recommended, // optional unless using "eslint:recommended"
    allConfig: js.configs.all,                 // optional unless using "eslint:all"
});

module.exports = [

    // mimic ESLintRC-style extends
    ...compat.extends("standard", "example", "plugin:react/recommended"),

    // mimic environments
    ...compat.env({
        es2020: true,
        node: true
    }),

    // mimic plugins
    ...compat.plugins("jsx-a11y", "react"),

    // translate an entire config
    ...compat.config({
        plugins: ["jsx-a11y", "react"],
        extends: "standard",
        env: {
            es2020: true,
            node: true
        },
        rules: {
            semi: "error"
        }
    })
];

Troubleshooting

TypeError: Missing parameter 'recommendedConfig' in FlatCompat constructor

The recommendedConfig option is required when any config uses eslint:recommended, including any config in an extends clause. To fix this, follow the example above using @eslint/js to provide the eslint:recommended config.

TypeError: Missing parameter 'allConfig' in FlatCompat constructor

The allConfig option is required when any config uses eslint:all, including any config in an extends clause. To fix this, follow the example above using @eslint/js to provide the eslint:all config.

License

MIT License