c12

What is c12?

The c12 npm package is a configuration loader and manager that helps in loading, merging, and managing configurations from various sources such as files, environment variables, and more. It is designed to be flexible and easy to use, making it suitable for a wide range of applications.

What are c12's main functionalities?

Loading Configuration from Files

This feature allows you to load configuration from files. The `loadConfig` function reads configuration files based on the provided options such as the name of the application and the current working directory.

const { loadConfig } = require('c12');

async function loadConfigExample() {
  const config = await loadConfig({
    name: 'myapp',
    cwd: process.cwd(),
    rcFile: true
  });
  console.log(config);
}

loadConfigExample();

Merging Configurations

This feature allows you to merge configurations from different sources. The `loadConfig` function can take default configurations and override configurations, merging them into a single configuration object.

const { loadConfig } = require('c12');

async function mergeConfigExample() {
  const config = await loadConfig({
    name: 'myapp',
    defaults: { key1: 'default1' },
    overrides: { key2: 'override2' }
  });
  console.log(config);
}

mergeConfigExample();

Loading Configuration from Environment Variables

This feature allows you to load configuration from environment variables. The `loadConfig` function can be configured to read environment variables with a specific prefix and include them in the configuration object.

const { loadConfig } = require('c12');

async function envConfigExample() {
  process.env.MYAPP_KEY = 'valueFromEnv';
  const config = await loadConfig({
    name: 'myapp',
    envPrefix: 'MYAPP_'
  });
  console.log(config);
}

envConfigExample();

Other packages similar to c12

config

The 'config' package is a popular configuration management tool for Node.js applications. It allows you to define configurations for different environments and load them based on the current environment. Compared to c12, 'config' is more opinionated and structured, making it easier to manage complex configurations but less flexible in terms of merging and loading from multiple sources.

dotenv

The 'dotenv' package loads environment variables from a .env file into process.env. It is simpler and more focused compared to c12, which offers more comprehensive configuration management capabilities including merging configurations from multiple sources.

rc

The 'rc' package is a non-opinionated configuration loader that reads configuration from various sources like files, environment variables, and command-line arguments. It is similar to c12 in terms of flexibility but lacks some of the advanced features like merging configurations and handling defaults and overrides.

README

c12

Smart Configuration Loader

Features

• JSON, CJS, Typescript and ESM config loader with unjs/jiti
• RC config support with unjs/rc9
• Multiple sources merged with unjs/defu
• .env support with dotenv
• Support extending nested configurations from multiple local or git sources

Usage

Install package:

# npm
npm install c12

# yarn
yarn add c12

# pnpm
pnpm install c12

Import:

// ESM
import { loadConfig } from 'c12'

// CommonJS
const { loadConfig } = require('c12')

Load configuration:

// Get loaded config
const { config } = await loadConfig({})

// Get resolved config and extended layers
const { config, configFile, layers } = await loadConfig({})

Loading priority

c12 merged config sources with unjs/defu by below order:

1. config overrides passed by options
2. config file in CWD
3. RC file in CWD
4. global RC file in user's home directory
5. default config passed by options
6. Extended config layers

Options

cwd

Resolve configuration from this working directory. Default is process.cwd()

name

Configuration base name. Default is config.

configName

Configuration file name without extension . Default is generated from name (name=foo => foo.config).

Set to false to avoid loading config file.

rcFile

RC Config file name. Default is generated from name (name=foo => .foorc).

Set to false to disable loading RC config.

globalRC

Load RC config from the workspace directory and user's home directory. Only enabled when rcFile is provided. Set to false to disable this functionality.

dotenv

Loads .env file if enabled. It is disabled by default.

defaults

Specify default configuration. It has the lowest priority and is applied after extending config.

defaultConfig

Specify default configuration. It is applied before extending config.

overides

Specify override configuration. It has the highest priority and is applied before extending config.

jiti

Custom unjs/jiti instance used to import configuration files.

jitiOptions

Custom unjs/jiti options to import configuration files.

Extending configuration

If resolved config contains a extends key, it will be used to extend configuration.

Extending can be nested and each layer can extend from one base or more.

Final config is merged result of extended options and user options with unjs/defu.

Each item in extends, is a string that can be either an absolute or relative path to current config file pointing to a config file for extending or directory containing config file. If it starts with either of github:, gitlab:, bitbucket: or https:, c12 autmatically clones it.

For custom merging strategies, you can directly access each layer with layers property.

Example:

// config.ts
export default {
  colors: {
    primary: 'user_primary'
  },
  extends: [
    './theme',
    './config.dev.ts'
  ]
}

// config.dev.ts
export default {
  dev: true
}

// theme/config.ts
export default {
  extends: '../base',
  colors: {
    primary: 'theme_primary',
    secondary: 'theme_secondary'
  }
}

// base/config.ts
export default {
  colors: {
    primary: 'base_primary'
    text: 'base_text'
  }
}

Loaded configuration would look like this:

{
  dev: true,
  colors: {
    primary: 'user_primary',
    secondary: 'theme_secondary',
    text: 'base_text'
  }
}

Layers:

[
 { config: /* theme config */, configFile: /* path/to/theme/config.ts */, cwd: /* path/to/theme */ },
 { config: /* base  config */, configFile: /* path/to/base/config.ts  */, cwd: /* path/to/base */ },
 { config: /* dev   config */, configFile: /* path/to/config.dev.ts  */, cwd: /* path/ */ },
]

💻 Development

• Clone this repository
• Enable Corepack using corepack enable (use npm i -g corepack for Node.js < 16.10)
• Install dependencies using pnpm install
• Run interactive tests using pnpm dev

License

Made with 💛 Published under MIT License.