README

Config Decorators

This is a configuration helper library that enables the efficient management of default dev settings and prod settings from environment variables. Useful for separating dev and prod environments, dockerization, etc.

Install

npm i config-decorators -S

Usage

Create a class with the config props
- Use inline settings for default values
- Use the ENV or CLI decorator to define overrides if the ENV variable / CLI argument is available
Instantiate the class with the loadConfig call
- You CAN instantiate the same class more than once
- You CAN create several classes with various decorators

Aaand... Done!

Config class

import { loadConfig, ENV } from './config-decorators';

export class Config {
    @ENV('MONGO_URL')
    mongoUrl = 'mongodb://localhost/test2';

    // Use it with a transform function
    @ENV('SERVER_PORT', parseInt)
    port = 8080;

    // Or use the 'number' shortcut
    @ENV('SERVER_PORT_2', 'number')
    @CLI('port2')
    port2 = 8081;

    // Rules for boolean values:
    // '0', '', 'false' will be parsed as `false`.
    // Everything else will be `true`.
    @ENV('ENABLE_AUTH', 'boolean')
    @CLI('enable-auth')
    enableAuth = true;
}

export const config = loadConfig(Config);

Import

import * as mongoose from 'mongoose';
import { config } from './config';

mongoose.connect(config.mongoUrl);

CLI variables

Note that CLI has higher priority than ENV. test.js:

class CliTest1 {
    @CLI('PATH')
    @ENV('PATH')
    path: string;
}
const config = loadConfig(CliTest1);
console.log(config.path);

When calling node test.js --PATH test will print test, not the PATH environmental variable.

Required variables

The ENV/CLI variable can be required; loadConfig will throw an error if there's no such ENV variable and no CLI argument. Note that NOT the class decorators but the loadConfig throws the error.

export class Config {
    @ENV('MONGO_URL', true)
    mongoUrl: string;

    @ENV('SERVER_PORT', parseInt, true)
    port: number;
}

// Here comes the error
export const config = loadConfig(Config);

How does it work?

The main stuff is at loadConfig:

First, it instantiates your class
Then it checks each prop having ENV or CLI decorators
- If there's no ENV/CLI variable with the given name then steps to next prop
- If there's a given transformator then the value is transformed
- Overrides the value of the prop

Tests

Clone the repo
npm i
npm run build -- You should have tsc (TypeScript) in your PATH
npm run test

Tested on Node.js with TypeScript (2.1.4+) classes, ES6 build.

Further Dev Plans -- NOT READY YET

Create an issue if you need something.

Validation

    @ENV('SERVER_PORT', parseInt)
    @Validate(value => value > 1000)
    port = 8080;

Print help

if (config.help) {
    printHelp(ConfigClass1, ConfigClass2); // <- here
    return;
}

Wider interface to minimist, e.g. aliases

Usage no npm install needed!