rc-config-loader/README.md

load config file from .{product}rc.{json,yml,js}

# rc-config-loader [![Actions Status: test](https://github.com/azu/rc-config-loader/workflows/test/badge.svg)](https://github.com/azu/rc-config-loader/actions?query=workflow%3A"test")

Load config from `.{product}rc.{json,yml,js}` file.

It is a Node.js library for loading `.textlintrc`, `.eslintrc`, `.stylelintrc` etc...

## Features

Find and load a configuration object from:

- a `package.json` property if it is needed
- a JSON or YAML, JS "rc file"
    - `.<product>rc` or `.<product>rc.json` or `.<product>rc.js` or`.<product>rc.yml`, `.<product>rc.yaml`
- TypeScript support
    - Includes `.d.ts`

## Difference

### with [MoOx/rc-loader](https://github.com/MoOx/rc-loader "MoOx/rc-loader")

- Safe API
    - `rc` contains shabang in `.js` file
- Enhance Error message

### with [cosmiconfig](https://github.com/davidtheclark/cosmiconfig "cosmiconfig")

- <del>Sync loading</del>
    - [cosmiconfig@3+](https://github.com/davidtheclark/cosmiconfig/blob/master/CHANGELOG.md#300) support `sync` option
- <del>Built-in TypeScript support</del>
    - [comisconfig@6*](https://github.com/davidtheclark/cosmiconfig/blob/master/CHANGELOG.md#600) is written by TypeScript

If you want to async support and customize loader, recommended to use [cosmiconfig](https://github.com/davidtheclark/cosmiconfig).

## Install

Install with [npm](https://www.npmjs.com/):

    npm install rc-config-loader

## Usage

### API

```ts
export interface rcConfigLoaderOption {
    // does look for `package.json`
    packageJSON?:
        | boolean
        | {
              fieldName: string;
          };
    // if config file name is not same with packageName, set the name
    configFileName?: string;
    // treat default(no ext file) as some extension
    defaultExtension?: string | string[];
    // where start to load
    cwd?: string;
}
/**
 * Find and load rcfile, return { config, filePath }
 * If not found any rcfile, throw an Error.
 * @param {string} pkgName
 * @param {rcConfigLoaderOption} [opts]
 * @returns {{ config: Object, filePath:string } | undefined}
 */
export declare function rcFile<R extends {}>(pkgName: string, opts?: rcConfigLoaderOption): {
    config: R;
    filePath: string;
} | undefined;

```

`rcFile` return `{ config, filePath }` object.

- `config`: it is config object
- `filePath`: absolute path to config file

**Note:**
 
- `rcFile` function return `undefined` if the config file is not found
- `rcFile` throw an Error if the config file content is malformed (causing a parsing error)

Recommenced usage:

```js
import { rcFile } from "rc-config-loader"

function loadRcFile(rcFileName){
    try {
        const results = rcFile(rcFileName);
        // Not Found
        if (!results) {
            return {};
        }
        return results.config;
    } catch (error) {
        // Found it, but it is parsing error
        return {} ; // default value
    }
}
// load config
const config = loadRcFile("your-application");
console.log(config); // => rcfile content
```

It will check these files and return config file if found it.

- `.your-applicationrc.json`
- `.your-applicationrc.yml`
- `.your-applicationrc.yaml`
- `.your-applicationrc.js`
- [optional] `package.json`
  - if `packageJSON` option is enabled

### Example

```js
import { rcFile } from "rc-config-loader"
// load .eslintrc from current dir
console.log(rcFile("eslint"));

// load .eslintrc from specific path
console.log(rcFile("eslint", {
    configFileName: `${__dirname}/test/fixtures/.eslintrc`
}));
/*
config: { extends: 'standard',
  rules:
   { 'comma-dangle': [ 2, 'always-multiline' ],
     'arrow-parens': [ 2, 'as-needed' ] } }
filePath: ${__dirname}/test/fixtures/.eslintrc
 */

// load property from package.json
console.log(rcFile("rc-config-loader", {
    packageJSON: {
        fieldName: "directories"
    }
}));
/*
config: { test: 'test' }
filePath: /path/to/package.json
 */

// load .eslintrc from specific dir
console.log(rcFile("eslint", {
    cwd: `${__dirname}/test/fixtures`
}));

// load specific filename from current dir
console.log(rcFile("travis", {configFileName: ".travis"}));
/*
config: { sudo: false, language: 'node_js', node_js: 'stable' }
filePath: /path/to/.travis
 */

// try to load as .json, .yml, js
console.log(rcFile("bar", {
    configFileName: `${__dirname}/test/fixtures/.barrc`,
    defaultExtension: [".json", ".yml", ".js"]
}));

// try to load as foobar, but .foobarrc is not found
console.log(rcFile("foorbar")); // => undefined

// try to load as .json, but it is not json
// throw SyntaxError
try {
    rcFile("unknown", {
        // This is not json
        configFileName: `${__dirname}/test/fixtures/.unknownrc`,
        defaultExtension: ".json"
    })
} catch (error) {
    console.log(error);
    /*
    SyntaxError: Cannot read config file: /test/fixtures/.unknownrc
    */
}
```

## Users

- [textlint](https://github.com/textlint/textlint "textlint")

## Changelog

See [Releases page](https://github.com/azu/rc-config-loader/releases).

## Running tests

Install devDependencies and Run `npm test`:

    npm i -d && npm test

## Contributing

Pull requests and stars are always welcome.

For bugs and feature requests, [please create an issue](https://github.com/azu/rc-config-loader/issues).

1. Fork it!
2. Create your feature branch: `git checkout -b my-new-feature`
3. Commit your changes: `git commit -am 'Add some feature'`
4. Push to the branch: `git push origin my-new-feature`
5. Submit a pull request :D

## Author

- [github/azu](https://github.com/azu)
- [twitter/azu_re](https://twitter.com/azu_re)

## License

MIT © azu

## Acknowledgement

- [zkochan/rcfile: Loads library configuration in all possible ways](https://github.com/zkochan/rcfile "zkochan/rcfile: Loads library configuration in all possible ways")

**Difference**

- support multiple `defaultExtension`