TS Convict

Annotate a class to define and validate your configs using convict just like you do with an ORM. Brings true serialized class types to your config when loaded. If you like annotating models classes with Typescript, then this package will work well. If your using a IOC/DI system, TSConvict will fit in real nice. The idea is inspired by projects like Typeorm and Inversify.

Quick Links

Contributing	Changelog	Convict

Requirements

• NodeJS 8+
• Typescript 3+
• Convict 5+

Features

• all the power and then some from convict
• define convict schemas with decorators
• get your config as serialized classes
• extremely simple and intuitive implementation
• very pretty code for defining your apps config

Installation

1. Install the package and dependencies.

npm install ts-convict convict reflect-metadata --save
npm install @types/convict --save-dev

Optionally install a parser of your choice if your config is not JSON. For example you can also use YAML.

npm install js-yaml --save

2. Make sure reflect-metadata Is configured correctly for Typescript.

2.1 tsconfig.json

"emitDecoratorMetadata": true,
"experimentalDecorators": true,

2.2 Import in main file
index.ts

import "reflect-metadata";

or import with node command
node -r reflect-metadata

Project Setup

First we need a proper project setup like the one below with a folder to hold our config schema classes. This is a very simple Typescript folder structure.

MyProject
├── src                  // place of your TypeScript code
│   ├── config           // place where your config entities will go
│   │   ├── MyConfig.ts  // the main config
│   │   ├── Database.ts  // sample database config
│   │   └── SubConfig.ts // a nested config
│   ├── types.d.ts       // place to put your interfaces  
│   └── index.ts         // start point of your application
├── .gitignore           // standard gitignore file
├── config.yml           // Your apps config file
├── db.json              // Your apps other db config as json
├── package.json         // node module dependencies
├── README.md            // a readme file
└── tsconfig.json        // TypeScript compiler options

Take note of the src/config directory, here we will put our convict schema classes.
The classes will be annotated with convict schema definitions. This directory can be called whatever you like.

Useage

1. Define an Interface

It's a good idea to define an interface so your experience can be agile and include all the fancy IDE features. Interfaces also open an opportunity to have more than one implementation of your config, i.e. maybe youswitch to a convict competitor or maybe just have no validation on config at all, i.e. require('config.json').

src/types.d.ts

declare namespace config {
    export interface MyConfig {
        name: string;
        subConfig: SubConfig;
        db: Database;
    }
    export interface SubConfig {
        bar: number;
    }
    export interface Database {
        host: string;
        port: number;
        database: string;
        user: string;
        password: string;
    }
}

2. Define a Schema Class

Now we can define a schema class and decorate it. The parameter for @Property decorator is simply a convict SchemaObj like in normal convict. You can read all about the possible options in convicts documentation.

src/config/MyConfig.ts

import { Property, Config } from 'ts-convict';
import SubConfig from './SubConfig';
import Database from './Database';
import * as yaml from 'js-yaml';
import { url, ipaddress } from "convict-format-with-validator";

@Config({
    
    // optional default file to load, no errors if it doesn't exist
    file: 'config.yml',// relative to NODE_PATH or cwd()

    // optional parameter. Defaults to 'strict', can also be 'warn' or 'skip'
    validationMethod: 'strict',

    // optionally add parsers like yaml or toml
    parser: { 
        extension: ['yml', 'yaml'], 
        parse: yaml.safeLoad
    },

    //optional extra formats to use in validation
    formats: {
        url,
        ipaddress,
    }
    
})
export class MyConfig implements config.MyConfig {
    
    // ts-convict will use the Typescript type if no format given
    @Property({
        doc: 'The name of the thing',
        default: 'Convict',
        env: 'MY_CONFIG_NAME'
    })
    public name: string;

    @Property(SubConfig)
    public subConfig: config.SubConfig;

    @Property(Database)
    public db: config.Database;

}

src/config/SubConfig.ts

import { Property } from 'ts-convict';

export class SubConfig implements config.SubConfig {
    @Property({
        doc: 'A sub prop',
        default: 3,
        env: 'SUB_CONFIG_BAR',
        format: 'int'
    })
    public bar: number;

    public message: string = "I am an unmanaged config property";
}

Database.ts

import { Property } from 'ts-convict';

export class Database implements config.Database {
    @Property({
        doc: "The database host",
        default: "localhost",
        format: "url",
        env: "DATABASE_HOST"
    })
    public host: string;

    @Property({
        doc: "The database port",
        default: 5432,
        format: "port",
        env: "DATABASE_PORT"
    })
    public port: number;

    @Property({
        doc: "The database db",
        default: "my_db",
        env: "DATABASE_DB"
    })
    public database: string;

    @Property({
        doc: "The database user",
        default: "magik",
        env: "DATABASE_USER"
    })
    public user: string;

    @Property({
        doc: "The database pass",
        default: "secretpassword",
        sensitive: true,
        env: "DATABASE_PASS"
    })
    public password: string;
}

3. Make a Configuration

Now we can make our configuration for our app. This can be a hardcoded Object in your code, a json file, a yaml file, or however you do it. In the end it's up to you how you type out and load the data.

config.yml

name: Cool App
subConfig: 
    bar: 5
db:
    user: devuser
    password: devpassword

db.json

{
    "user": "someuser",
    "password": "somepassword",
    "host": "somedb.com"
}

4. Load it up

We have a couple of ways to load it up so you can choose what works for your unique situation. The example below is the simplest way in the spirit of TL;DR.

src/index.ts

import { TSConvict } from 'ts-convict';
import { MyConfig } from "./config/MyConfig";
import { Database } from "./config/Database";
import { SubConfig } from "./config/SubConfig";

// example loading default file defined in @Config
const myConfigLoader = new TSConvict<MyConfig>(MyConfig);
const myConfig: MyConfig = myConfigLoader.load();

// example loading with file passed to load
const dbLoader = new TSConvict<Database>(Database);
const dbConfig: Database = dbLoader.load('db.json');

// example loading an ad hoc config class with raw data
const rawSub: config.SubConfig = {
    bar: 22
};
const subLoader = new TSConvict<SubConfig>(SubConfig);
const subConfig = subLoader.load(rawSub);