⚙️ 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
.envsupport with dotenv- Reads config from the nearest
package.jsonfile - Extends configurations from multiple local or git sources
- Overwrite with environment-specific configuration
- Config watcher with auto-reload and HMR support
Usage
Install package:
# npm
npm install c12
# yarn
yarn add c12
# pnpm
pnpm install c12Import:
// ESM
import { loadConfig, watchConfig } from "c12";
// CommonJS
const { loadConfig, watchConfig } = 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:
- Config overrides passed by options
- Config file in CWD
- RC file in CWD
- Global RC file in the user's home directory
- Config from
package.json - Default config passed by options
- Extended config layers
Options
cwd
Resolve configuration from this working directory. The default is process.cwd()
name
Configuration base name. The default is config.
configFile
Configuration file name without extension. Default is generated from name (f.e., if name is foo, the config file will be => foo.config).
Set to false to avoid loading the 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 the 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.
packageJson
Loads config from nearest package.json file. It is disabled by default.
If true value is passed, c12 uses name field from package.json.
You can also pass either a string or an array of strings as a value to use those fields.
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.
overrides
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.
envName
Environment name used for environment specific configuration.
The default is process.env.NODE_ENV. You can set envName to false or an empty string to disable the feature.
Extending configuration
If resolved config contains a extends key, it will be used to extend the configuration.
Extending can be nested and each layer can extend from one base or more.
The 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 the current config file pointing to a config file for extending or the directory containing the config file.
If it starts with either github:, gitlab:, bitbucket:, or https:, c12 automatically 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
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'
}
}The 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/ */ },
]Environment-specific configuration
Users can define environment-specific configuration using these config keys:
$test: {...}$development: {...}$production: {...}$env: { [env]: {...} }
c12 tries to match envName and override environment config if specified.
Note: Environment will be applied when extending each configuration layer. This way layers can provide environment-specific configuration.
Example:
{
// Default configuration
logLevel: 'info',
// Environment overrides
$test: { logLevel: 'silent' },
$development: { logLevel: 'warning' },
$production: { logLevel: 'error' },
$env: {
staging: { logLevel: 'debug' }
}
}Watching Configuration
you can use watchConfig instead of loadConfig to load config and watch for changes, add and removals in all expected configuration paths and auto reload with new config.
Lifecycle hooks
onWatch: This function is always called when config is updated, added, or removed before attempting to reload the config.acceptHMR: By implementing this function, you can compare old and new functions and returntrueif a full reload is not needed.onUpdate: This function is always called after the new config is updated. IfacceptHMRreturns true, it will be skipped.
import { watchConfig } from "c12";
const config = watchConfig({
cwd: ".",
// chokidarOptions: {}, // Default is { ignoreInitial: true }
// debounce: 200 // Default is 100. You can set it to false to disable debounced watcher
onWatch: (event) => {
console.log("[watcher]", event.type, event.path);
},
acceptHMR({ oldConfig, newConfig, getDiff }) {
const diff = getDiff();
if (diff.length === 0) {
console.log("No config changed detected!");
return true; // No changes!
}
},
onUpdate({ oldConfig, newConfig, getDiff }) {
const diff = getDiff();
console.log("Config updated:\n" + diff.map((i) => i.toJSON()).join("\n"));
},
});
console.log("watching config files:", config.watchingFiles);
console.log("initial config", config.config);
// Stop watcher when not needed anymore
// await config.unwatch();💻 Development
- Clone this repository
- Enable Corepack using
corepack enable(usenpm i -g corepackfor Node.js < 16.10) - Install dependencies using
pnpm install - Run interactive tests using
pnpm dev
License
Made with