feat: More cli client tests and documentation.

Sources/CliClient/EnvironmentDependency.swift

@@ -24,11 +24,7 @@ public extension DependencyValues {
 @DependencyClient
 public struct EnvironmentDependency: Sendable {
 
-  /// A json decoder to use to decode files and environment variables.
-  public var jsonDecoder: @Sendable () -> JSONDecoder = { JSONDecoder() }
-
-  /// A json encoder to use to encode files and environment variables.
-  public var jsonEncoder: @Sendable () -> JSONEncoder = { JSONEncoder() }
+  public var coders: @Sendable () -> any Coderable = { JSONCoders() }
 
   /// Load the variables based on the request.
   public var load: @Sendable (FileType) async throws -> [String: String] = { _ in [:] }
@@ -61,6 +57,8 @@ public struct EnvironmentDependency: Sendable {
   }
 }
 
+struct DecodeError: Error {}
+
 @_spi(Internal)
 extension EnvironmentDependency: DependencyKey {
 
@@ -71,8 +69,7 @@ extension EnvironmentDependency: DependencyKey {
     encoder: JSONEncoder = .init()
   ) -> Self {
     Self(
-      jsonDecoder: { decoder },
-      jsonEncoder: { encoder },
+      coders: { JSONCoders(decoder: decoder, encoder: encoder) },
       load: { file in
         switch file {
         case let .dotEnv(path: path):
@@ -95,6 +92,39 @@ extension EnvironmentDependency: DependencyKey {
   public static let liveValue: EnvironmentDependency = .live()
 }
 
+/// A type that encode and decode values.
+///
+/// This is really just here to override tests with coders that will throw an error,
+/// instead of encoding or decoding data.
+///
+@_spi(Internal)
+public protocol Coderable {
+  func encode<T: Encodable>(_ instance: T) throws -> Data
+  func decode<T: Decodable>(_ type: T.Type, from data: Data) throws -> T
+}
+
+struct JSONCoders: Coderable {
+
+  let decoder: JSONDecoder
+  let encoder: JSONEncoder
+
+  init(
+    decoder: JSONDecoder = .init(),
+    encoder: JSONEncoder = .init()
+  ) {
+    self.decoder = decoder
+    self.encoder = encoder
+  }
+
+  func encode<T>(_ instance: T) throws -> Data where T: Encodable {
+    try encoder.encode(instance)
+  }
+
+  func decode<T>(_ type: T.Type, from data: Data) throws -> T where T: Decodable {
+    try decoder.decode(T.self, from: data)
+  }
+}
+
 private func url(for path: String) -> URL {
   #if os(Linux)
     return URL(fileURLWithPath: path)