Veil

Veil is a small layer to help with configs and environment variables in Scala applications.

Environment Variables

Veil provides a simple way to access environment variables through both .env files and system environment variables. The environment loading is determined by the SCALA_ENV environment variable, which can be:

• DEV (default) - loads from .env
• TEST - loads from .env.test
• PROD - loads from .env.prod

You can access environment variables using:

Veil.get(key: String): Option[String]

This will first check the loaded .env file, then fall back to System.getenv() if not found. Values in .env files that are quoted will have their quotes automatically stripped.

Configuration Files

Veil provides a Config type-class for loading and parsing JSON configuration files into case classes. This makes it easy to load typed configuration from either files or resources.

Example usage:

// Define your config case class
case class AppConfig(host: String, port: Int) derives Config

// Load from a resource file
val config: Try[AppConfig] = Config.of[AppConfig].fromResource("app-config.json")

// Or load from a file path
val config: Try[AppConfig] = Config.of[AppConfig].fromFile("config/app-config.json")

The Config type-class will automatically handle JSON parsing and mapping to your case class. It uses the Friday JSON library under the hood.

Auto-Derivation

The Config type-class can be automatically derived for any case class that has a JsonDecoder instance available. You can either:

1. Use the derives Config syntax as shown above
2. Let the compiler auto-derive it implicitly

Both approaches work equivalently:

// Explicit derivation
case class AppConfig(host: String, port: Int) derives Config

// Implicit derivation
case class AppConfig2(host: String, port: Int)
val config = Config.of[AppConfig2].fromResource("config.json")

This makes it easy to load strongly-typed configuration with minimal boilerplate code.