separate protocol for simpler lambda (no init)

Author: tomerd

Examples/Benchmark/BenchmarkHandler.swift

@@ -22,9 +22,6 @@ import NIOCore
 
 @main
 struct BenchmarkHandler: EventLoopLambdaHandler {
-    typealias Event = String
-    typealias Output = String
-
     static func makeHandler(context: LambdaInitializationContext) -> EventLoopFuture<Self> {
         context.eventLoop.makeSucceededFuture(BenchmarkHandler())
     }

Examples/Deployment/Sources/Benchmark/BenchmarkHandler.swift

@@ -22,9 +22,6 @@ import NIOCore
 
 @main
 struct BenchmarkHandler: EventLoopLambdaHandler {
-    typealias Event = String
-    typealias Output = String
-
     static func makeHandler(context: LambdaInitializationContext) -> EventLoopFuture<Self> {
         context.eventLoop.makeSucceededFuture(BenchmarkHandler())
     }

Examples/Deployment/Sources/HelloWorld/HelloWorldHandler.swift

@@ -16,7 +16,7 @@ import AWSLambdaRuntime
 
 // introductory example, the obligatory "hello, world!"
 @main
-struct HelloWorldHandler: LambdaHandler {
+struct HelloWorldHandler: SimpleLambdaHandler {
     func handle(_ event: String, context: LambdaContext) async throws -> String {
         "hello, world"
     }

Examples/Echo/Lambda.swift

@@ -17,7 +17,7 @@ import AWSLambdaRuntime
 // in this example we are receiving and responding with strings
 
 @main
-struct MyLambda: LambdaHandler {
+struct MyLambda: SimpleLambdaHandler {
     func handle(_ input: String, context: LambdaContext) async throws -> String {
         // as an example, respond with the input's reversed
         String(input.reversed())

Examples/ErrorHandling/Lambda.swift

@@ -17,10 +17,7 @@ import AWSLambdaRuntime
 // MARK: - Run Lambda
 
 @main
-struct MyLambda: LambdaHandler {
-    typealias Event = Request
-    typealias Output = Response
-
+struct MyLambda: SimpleLambdaHandler {
     func handle(_ request: Request, context: LambdaContext) async throws -> Response {
         // switch over the error type "requested" by the request, and trigger such error accordingly
         switch request.error {

Examples/Foundation/Lambda.swift

@@ -25,9 +25,6 @@ import Logging
 
 @main
 struct MyLambda: LambdaHandler {
-    typealias Event = Request
-    typealias Output = [Exchange]
-
     let calculator: ExchangeRatesCalculator
 
     init(context: LambdaInitializationContext) async throws {

Examples/JSON/Lambda.swift

@@ -26,10 +26,7 @@ struct Response: Codable {
 // codables to model your request and response objects
 
 @main
-struct MyLambda: LambdaHandler {
-    typealias Event = Request
-    typealias Output = Response
-
+struct MyLambda: SimpleLambdaHandler {
     func handle(_ event: Request, context: LambdaContext) async throws -> Response {
         // as an example, respond with the input event's reversed body
         Response(body: String(event.body.reversed()))

Examples/LocalDebugging/MyLambda/Lambda.swift

@@ -19,10 +19,7 @@ import Shared
 // a local server simulator which will allow local debugging
 
 @main
-struct MyLambda: LambdaHandler {
-    typealias Event = Request
-    typealias Output = Response
-
+struct MyLambda: SimpleLambdaHandler {
     func handle(_ request: Request, context: LambdaContext) async throws -> Response {
         // TODO: something useful
         Response(message: "Hello, \(request.name)!")

Examples/Testing/Sources/Lambda.swift

@@ -17,7 +17,7 @@ import AWSLambdaRuntime
 // in this example we are receiving and responding with strings
 
 @main
-struct MyLambda: LambdaHandler {
+struct MyLambda: SimpleLambdaHandler {
     func handle(_ event: String, context: LambdaContext) async throws -> String {
         // as an example, respond with the event's reversed body
         String(event.reversed())

Sources/AWSLambdaRuntimeCore/Lambda+String.swift

@@ -19,7 +19,7 @@ import NIOCore
 extension LambdaHandler where Event == String {
     /// Implementation of a `ByteBuffer` to `String` decoding.
     @inlinable
-    public func decode(buffer: ByteBuffer) throws -> String {
+    public func decode(buffer: ByteBuffer) throws -> Event {
         guard let value = buffer.getString(at: buffer.readerIndex, length: buffer.readableBytes) else {
             throw CodecError.invalidString
         }
@@ -31,7 +31,7 @@ extension LambdaHandler where Event == String {
 extension LambdaHandler where Output == String {
     /// Implementation of `String` to `ByteBuffer` encoding.
     @inlinable
-    public func encode(value: String, into buffer: inout ByteBuffer) throws {
+    public func encode(value: Output, into buffer: inout ByteBuffer) throws {
         buffer.writeString(value)
     }
 }
@@ -41,7 +41,7 @@ extension LambdaHandler where Output == String {
 extension EventLoopLambdaHandler where Event == String {
     /// Implementation of `String` to `ByteBuffer` encoding.
     @inlinable
-    public func decode(buffer: ByteBuffer) throws -> String {
+    public func decode(buffer: ByteBuffer) throws -> Event {
         guard let value = buffer.getString(at: buffer.readerIndex, length: buffer.readableBytes) else {
             throw CodecError.invalidString
         }
@@ -52,7 +52,7 @@ extension EventLoopLambdaHandler where Event == String {
 extension EventLoopLambdaHandler where Output == String {
     /// Implementation of a `ByteBuffer` to `String` decoding.
     @inlinable
-    public func encode(value: String, into buffer: inout ByteBuffer) throws {
+    public func encode(value: Output, into buffer: inout ByteBuffer) throws {
         buffer.writeString(value)
     }
 }

Sources/AWSLambdaRuntimeCore/LambdaHandler.swift

@@ -15,11 +15,31 @@
 import Dispatch
 import NIOCore
 
+// MARK: - SimpleLambdaHandler
+
+/// Strongly typed, processing protocol for a Lambda that takes a user defined
+/// ``LambdaHandler/Event`` and returns a user defined
+/// ``LambdaHandler/Output`` asynchronously.
+///
+/// - note: Most users should implement the ``LambdaHandler`` protocol instead
+///         which defines the Lambda initialization method.
+@available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+public protocol SimpleLambdaHandler: LambdaHandler {
+    init()
+}
+
+@available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
+extension SimpleLambdaHandler {
+    public init(context: LambdaInitializationContext) async throws {
+        self.init()
+    }
+}
+
 // MARK: - LambdaHandler
 
 /// Strongly typed, processing protocol for a Lambda that takes a user defined
-/// ``EventLoopLambdaHandler/Event`` and returns a user defined
-/// ``EventLoopLambdaHandler/Output`` asynchronously.
+/// ``LambdaHandler/Event`` and returns a user defined
+/// ``LambdaHandler/Output`` asynchronously.
 ///
 /// - note: Most users should implement this protocol instead of the lower
 ///         level protocols ``EventLoopLambdaHandler`` and
@@ -33,8 +53,12 @@ public protocol LambdaHandler {
     /// The lambda function's output. Can be `Void`.
     associatedtype Output
 
-    init()
-
+    /// The Lambda initialization method.
+    /// Use this method to initialize resources that will be used in every request.
+    ///
+    /// Examples for this can be HTTP or database clients.
+    /// - parameters:
+    ///     - context: Runtime ``LambdaInitializationContext``.
     init(context: LambdaInitializationContext) async throws
 
     /// The Lambda handling method.
@@ -66,23 +90,6 @@ public protocol LambdaHandler {
     func decode(buffer: ByteBuffer) throws -> Event
 }
 
-@available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
-extension LambdaHandler {
-    public init() {
-        self.init()
-    }
-
-    /// The Lambda initialization method.
-    /// Use this method to initialize resources that will be used in every request.
-    ///
-    /// Examples for this can be HTTP or database clients.
-    /// - parameters:
-    ///     - context: Runtime ``LambdaInitializationContext``.
-    public init(context: LambdaInitializationContext) async throws {
-        self.init()
-    }
-}
-
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 final class CodableLambdaHandler<Underlying: LambdaHandler>: ByteBufferLambdaHandler {
     private let handler: Underlying
@@ -133,7 +140,7 @@ final class CodableLambdaHandler<Underlying: LambdaHandler>: ByteBufferLambdaHan
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
 extension LambdaHandler where Output == Void {
     @inlinable
-    public func encode(value: Void, into buffer: inout ByteBuffer) throws {}
+    public func encode(value: Output, into buffer: inout ByteBuffer) throws {}
 }
 
 @available(macOS 12, iOS 15, tvOS 15, watchOS 8, *)
@@ -173,10 +180,7 @@ internal struct UncheckedSendableHandler<Underlying: LambdaHandler, Event, Outpu
 // MARK: - EventLoopLambdaHandler
 
 /// Strongly typed, `EventLoopFuture` based processing protocol for a Lambda that takes a user
-/// defined ``Event`` and returns a user defined ``Output`` asynchronously.
-///
-/// ``EventLoopLambdaHandler`` extends ``ByteBufferLambdaHandler``, performing
-/// `ByteBuffer` -> ``Event`` decoding and ``Output`` -> `ByteBuffer` encoding.
+/// defined ``EventLoopLambdaHandler/Event`` and returns a user defined ``EventLoopLambdaHandler/Output`` asynchronously.
 ///
 /// - note: To implement a Lambda, implement either ``LambdaHandler`` or the
 ///         ``EventLoopLambdaHandler`` protocol. The ``LambdaHandler`` will offload
@@ -235,7 +239,7 @@ public protocol EventLoopLambdaHandler {
 /// Implementation of `ByteBuffer` to `Void` decoding.
 extension EventLoopLambdaHandler where Output == Void {
     @inlinable
-    public func encode(value: Void, into buffer: inout ByteBuffer) throws {}
+    public func encode(value: Output, into buffer: inout ByteBuffer) throws {}
 }
 
 internal final class CodableEventLoopLambdaHandler<Underlying: EventLoopLambdaHandler>: ByteBufferLambdaHandler {