@zarja/config NPM

Config

Library enables typesafe environment configuration and allows overrides from .env.<environment> files or environment variables, similar to Microprofile.

Usage

import { Var, initializeEnvironment } from '@zarja/config'
import { LogLevel } from './logger'

export const config = initializeEnvironment({
  port: Var.number(8080),
  db: {
    url: Var.string(),
  },
  log: {
    level: Var.enum(LogLevel).default(LogLevel.INFO),
  },
  server: {
    greeting: Var.string('Hello').transform((message, ctx) => `${message}, ${ctx.info.env}!`), // Hello, local!
  },
})

Then in .env.local:

# Provide database url for path db.url
DB_URL=postgres://localhost:5432/db

# Override default port
PORT=3000

Motivation

A library that would glue configuration and validation together does not seem to exist in Typescript or when it does, it seems to be clunky (looking at you @nestjs/config). Working with pure process.env turns into a pain, because you would have to validate it every time you use it across the codebase. We can address both "validate it" and "across the codebase", by specifying environment variables that we need in a single file and validating them using a validation library of choice:

const schema = /* schema definition */

export const config = schema.validate(process.env)

But this gives us a flat config structure with UPPERCASE_VARIABLES by convention. To improve this, we can do the following:

const schema = /* schema definition */

const definition = {
    db: {
        url: process.env.DB_URL
    }
}

export const config = schema.validate(definition)

However, the ergonomics of this are shitty, because you have to always update schema and definition for the same reason. There is inherent disconnect between the two, that this project intends to address.