# 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:
```shell
npm install @eslint/eslintrc -D
# or
yarn add @eslint/eslintrc -D
# or
pnpm install @eslint/eslintrc -D
# or
bun install @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:
```js
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:
```js
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
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