ConfigKeyKit

A tiny, dependency-free Swift package for defining configuration keys that resolve consistently across multiple sources (command-line arguments, environment variables, …).

ConfigKeyKit pairs naturally with apple/swift-configuration but does not depend on it — the package is intentionally Foundation-only so it can be adopted by any Swift app or library without pulling in a configuration framework.

What's inside

A single ConfigKeyKit product bundles:

• Key types — ConfigKey, OptionalConfigKey, ConfigurationKey, NamingStyle, StandardNamingStyle, ConfigKeySource.
• CLI scaffolding — Command, CommandRegistry, CommandLineParser, ConfigurationParseable. A lightweight command-dispatch pattern you can ignore if you only need keys.

Usage

import ConfigKeyKit

let containerID = ConfigKey<String>(
  "cloudkit.container_id",
  envPrefix: "MYAPP",
  default: "iCloud.com.example.MyApp"
)

containerID.key(for: .commandLine)   // "cloudkit.container_id"
containerID.key(for: .environment)   // "MYAPP_CLOUDKIT_CONTAINER_ID"
containerID.defaultValue             // "iCloud.com.example.MyApp"

You then feed those resolved key strings into whatever provider stack you prefer (Swift Configuration, environment lookup, manual argument parsing, …).

Pairing with swift-configuration

ConfigKey resolves a single base key into per-source strings, which slots neatly into swift-configuration's provider stack. Each provider sees the key name it expects (dot-separated for CLI, screaming snake case for ENV), while your call site stays declarative:

import Configuration
import ConfigKeyKit

let containerID = ConfigKey<String>(
  "cloudkit.container_id",
  envPrefix: "MYAPP",
  default: "iCloud.com.example.MyApp"
)

let config = ConfigReader(providers: [
  CommandLineArgumentsProvider(),
  EnvironmentVariablesProvider(),
])

extension ConfigReader {
  func string<Value>(for key: ConfigKey<Value>) -> String where Value == String {
    if let cli = key.key(for: .commandLine),
       let value = self.string(forKey: cli) {
      return value
    }
    if let env = key.key(for: .environment),
       let value = self.string(forKey: env) {
      return value
    }
    return key.defaultValue
  }
}

let resolved = config.string(for: containerID)
// Looks up "cloudkit.container_id" on the CLI, falls back to
// "MYAPP_CLOUDKIT_CONTAINER_ID" in the environment, then the default.

Used by

• MistDemo — the demo app inside MistKit.
• BushelCloud.

Adding to your Package.swift

.package(url: "https://github.com/brightdigit/ConfigKeyKit.git", from: "1.0.0-beta.1"),

.target(
  name: "MyApp",
  dependencies: [
    .product(name: "ConfigKeyKit", package: "ConfigKeyKit"),
  ]
),

License

MIT — see LICENSE.