@cybozu/eslint-config/README.md

ESLint rules for Cybozu

# @cybozu/eslint-config

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A ESLint rule set for Cybozu.

**This package is intended to use in Cybozu. Currently, this is still in development so the rules might be changed.**

## What is this?

This is a ESLint rule set for Cybozu.
The purpose of `@cybozu/eslint-config` are following

- Share best practices for JavaScript
- Standardize JavaScript coding guideline in Cybozu
- Installation support for ESLint and continuous support for the rule set

## The benefits to adapt this rule

You don't need to care about updates for ESLint and ESLint plugins.
We'll manage the updates and provide CHANGELOG that you need to know so that you can update it easily.
In addition, we'll add some useful plugins into `@cybozu/eslint-config` so you can learn about best practices for JavaScript through `@cybozu/eslint-config`.

## Rule set policies

We provide rules that are Error or Warning.

### Error

This is a rule you must fix because the code might not follow our practices in JavaScript

### Warning

This is a rule you should fix because the code style might not be preferable.

## Version policy

1.  We update major version if the changes might cause new errors.
1.  We update minor version if the changes might cause new warnings.
1.  We update patch version if the changes don't cause any new errors and warnings.

## How to use

Install `eslint` and `@cybozu/eslint-config`

```
% npm install --save-dev eslint @cybozu/eslint-config
```

### `.eslintrc.js`

Put it into your `.eslintrc.js`

```js
module.exports = {
  extends: "@cybozu"
};
```

**Currently, we adopt that `indent` rule is 2 spaces and having indentation in `switch case`.
You can override the rule if your project adopts 4 spaces or others.
We think it's important to have consistency in your entire codebase.**

```js
module.exports = {
  extends: "@cybozu/eslint-config/presets/react-typescript-prettier",
  rules: {
    // default
    // 'indent': ['warn', 2, { "SwitchCase": 1 }],
    indent: ["warn", 4, { SwitchCase: 0 }]
  }
};
```

### `eslint.config.js` (Flat Config)

> [!NOTE]
> Flat Config support is experimental. The applicable rules and scope may have changed.

Put it into your `eslint.config.js`

```js
const config = require("@cybozu/eslint-config/flat/presets/react-typescript-prettier")

module.exports = [
  ...config,
  {
    rules: {
      // default
      // 'indent': ['warn', 2, { "SwitchCase": 1 }],
      indent: ["warn", 4, { SwitchCase: 0 }]
    }
  },
]
```

## Support rule set

- `@cybozu`
  - or `@cybozu/eslint-config/flat/presets/base` for Flat Config
  - This is included in the all following presets
- `@cybozu/eslint-config/presets/node`
  - or `@cybozu/eslint-config/flat/presets/node` for Flat Config
  - Including `eslint-plugin-n`
- `@cybozu/eslint-config/presets/typescript`
  - or `@cybozu/eslint-config/flat/presets/typescript` for Flat Config
  - Including `@typescript-eslint/eslint-plugin`
- `@cybozu/eslint-config/presets/react`
  - or `@cybozu/eslint-config/flat/presets/react` for Flat Config
  - Including `eslint-plugin-react`, `eslint-plugin-jsx-ally` and `eslint-plugin-react-hooks`
- `@cybozu/eslint-config/presets/react-typescript`
  - or `@cybozu/eslint-config/flat/presets/react-typescript` for Flat Config
  - Including `@cybozu/eslint-config/presets/typescript` and `@cybozu/eslint-config/presets/react`
- `@cybozu/eslint-config/presets/es5`
  - or `@cybozu/eslint-config/flat/presets/es5` for Flat Config

## Prettier Support

Prettier is a code formatter, which supports not only JavaScript but also many languages.
Prettier is used widely as code formatter for JavaScript.

It's opinionated but we don't have to discuss about code styles with Prettier because it's the rule (No more bikeshed).

The following presets disable all rules that conflict with Prettier and treat the differences between Prettier's code format as errors.
You can fix the errors by `--fix` option so you don't have to fix the errors manually.

To use the presets, you have to install `prettier`. We only support Prettier v2 or later versions.

```
% npm install --save-dev prettier
```

- `@cybozu/eslint-config/presets/prettier`
- `@cybozu/eslint-config/presets/node-prettier`
- `@cybozu/eslint-config/presets/node-typescript-prettier`
- `@cybozu/eslint-config/presets/typescript-prettier`
- `@cybozu/eslint-config/presets/react-typescript-prettier`
- `@cybozu/eslint-config/presets/react-prettier`
- `@cybozu/eslint-config/presets/es5-prettier`

**Currently, we don't support customized Prettier config**

## React Support

### ⚠️ Classic JSX Syntax

`@cybozu/eslint-config` is intented to be used with the [New JSX Transform](https://reactjs.org/blog/2020/09/22/introducing-the-new-jsx-transform.html). If you want to use the Classic JSX Transform (`React.createElement`), please enable the `react/jsx-uses-react` rule on your own.

```js
rules: {
  "react/jsx-uses-react": "error"
}
```

## For kintone customize developers

We also provide presets for kintone customize/plug-in developers, which include some `globals` for kintone.

### Usage

```js
// .eslintrc.js
module.exports = {
  extends: "@cybozu/eslint-config/presets/kintone-customize"
};
```

### Presets

- `@cybozu/eslint-config/preset/kintone-customize`
  - or `@cybozu/eslint-config/flat/presets/kintone-customize` for Flat Config
  - Preset for kintone customize/plugin-in development
- `@cybozu/eslint-config/preset/kintone-customize-prettier`
  - or `@cybozu/eslint-config/flat/presets/kintone-customize-prettier` for Flat Config
  - Preset for kintone customize/plugin-in development including `prettier` config
- `@cybozu/eslint-config/preset/kintone-customize-es5`
  - or `@cybozu/eslint-config/flat/presets/kintone-customize-es5` for Flat Config
  - Preset for kintone customize/plugin-in development in ES5
- `@cybozu/eslint-config/preset/kintone-customize-es5-prettier`
  - or `@cybozu/eslint-config/flat/presets/kintone-customize-es5-prettier` for Flat Config
  - Preset for kintone customize/plugin-in development in ES5 including `prettier` config