eslint-plugin-optimal-modules/readme.md

An ESLint plugin to enforce optimal JavaScript module design.

# eslint-plugin-optimal-modules

An [ESLint plugin](https://eslint.org/docs/latest/use/configure/plugins) to enforce [optimal JavaScript module design](https://jaydenseric.com/blog/optimal-javascript-module-design).

## Installation

To install [`eslint-plugin-optimal-modules`](https://npm.im/eslint-plugin-optimal-modules) with [npm](https://docs.npmjs.com/downloading-and-installing-node-js-and-npm), run:

```sh
npm install eslint-plugin-optimal-modules --save-dev
```

To use the [recommended config](#config-recommended), add the following ESLint “flat” config in [`eslint.config.mjs`](https://eslint.org/docs/latest/use/configure/configuration-files#configuration-file):

```js
// @ts-check

import eslintPluginOptimalModules from "eslint-plugin-optimal-modules";

/**
 * ESLint config.
 * @satisfies {Array<import("eslint").Linter.Config>}
 */
const eslintConfig = [eslintPluginOptimalModules.configs.recommended];

export default eslintConfig;
```

Alternatively, manually configure the plugin and the desired rules:

```js
// @ts-check

import eslintPluginOptimalModules from "eslint-plugin-optimal-modules";

/**
 * ESLint config.
 * @satisfies {Array<import("eslint").Linter.Config>}
 */
const eslintConfig = [
  {
    plugins: {
      "optimal-modules": eslintPluginOptimalModules,
    },
    rules: {
      "optimal-modules/no-named-exports": "error",
    },
  },
];

export default eslintConfig;
```

To allow named exports in [Storybook](https://storybook.js.org) story modules that have a [Component Story Format (CSF)](https://github.com/ComponentDriven/csf):

```js
// @ts-check

import eslintPluginOptimalModules from "eslint-plugin-optimal-modules";

/**
 * ESLint config.
 * @satisfies {Array<import("eslint").Linter.Config>}
 */
const eslintConfig = [
  eslintPluginOptimalModules.configs.recommended,
  {
    files: ["**/*.stories.{mjs,cjs,js,mts,cts,ts,tsx}"],
    rules: {
      "optimal-modules/no-named-exports": "off",
    },
  },
];

export default eslintConfig;
```

## Rules

### Rule `no-named-exports`

Prohibits using named exports for [optimal module design](https://jaydenseric.com/blog/optimal-javascript-module-design).

**Valid** examples:

```js
// No exports.
const a = true;
```

```js
// Default export.
export default true;
```

```js
// Default export.
const a = true;
export { a as default };
```

```ts
// TypeScript type default export.
type A = boolean;
export type { A as default };
```

**Invalid** examples:

```js
// Named export.
export const a = true;
```

```js
// Named export.
const a = true;
export { a };
```

```ts
// TypeScript type named export.
export type A = boolean;
```

To fix the above errors, move the thing being exported to its own module as a default export.

## Configs

### Config `recommended`

Enabled rules:

- [`no-named-exports`](#rule-no-named-exports) (error).

## Requirements

Supported runtime environments:

- [Node.js](https://nodejs.org) versions `^18.18.0 || ^20.9.0 || >=21.1.0`.

Projects must configure [TypeScript](https://typescriptlang.org) to use types from the CommonJS modules that have a `// @ts-check` comment:

- [`compilerOptions.allowJs`](https://typescriptlang.org/tsconfig#allowJs) should be `true`.
- [`compilerOptions.maxNodeModuleJsDepth`](https://typescriptlang.org/tsconfig#maxNodeModuleJsDepth) should be reasonably large, e.g. `10`.
- [`compilerOptions.module`](https://typescriptlang.org/tsconfig#module) should be `"node16"` or `"nodenext"`.

## Exports

These CommonJS modules are exported via the [`package.json`](./package.json) field [`exports`](https://nodejs.org/api/packages.html#exports):

- [`eslintPluginOptimalModules.js`](./eslintPluginOptimalModules.js)