API Refactoring (#273)

motivation: define stable API in preperation 1.0 release

changes:
* require swift 5.7, remove redundant backwards compatibility code
* make LambdaHandler, EventLoopLambdaHandler, and ByteBufferLambdaHandler disjointed protocols to reduce API surface area
* create coding wrappers for LambdaHandler and EventLoopLambdaHandler to provide bridge to ByteBufferLambdaHandler
* reuse output ByteBuffer to reduce allocations
* add new SimpleLambdaHandler with no-op initializer for simple lambda use cases
* update callsites and tests
* update examples

Co-authored-by: Yim Lee <yim_lee@apple.com>
Co-authored-by: Fabian Fett <fabianfett@apple.com>

Author: 3 people

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/Benchmark/Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.5
+// swift-tools-version:5.7
 
 import PackageDescription
 

Examples/Deployment/Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.5
+// swift-tools-version:5.7
 
 import PackageDescription
 

Examples/Deployment/Sources/Benchmark/BenchmarkHandler.swift

@@ -13,7 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 import AWSLambdaRuntimeCore
-import NIO
+import NIOCore
 
 // If you would like to benchmark Swift's Lambda Runtime,
 // use this example which is more performant.
@@ -22,9 +22,6 @@ import NIO
 
 @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

@@ -16,14 +16,7 @@ import AWSLambdaRuntime
 
 // introductory example, the obligatory "hello, world!"
 @main
-struct HelloWorldHandler: LambdaHandler {
-    typealias Event = String
-    typealias Output = String
-
-    init(context: LambdaInitializationContext) async throws {
-        // setup your resources that you want to reuse here.
-    }
-
+struct HelloWorldHandler: SimpleLambdaHandler {
     func handle(_ event: String, context: LambdaContext) async throws -> String {
         "hello, world"
     }

Examples/Echo/Lambda.swift

@@ -17,14 +17,7 @@ import AWSLambdaRuntime
 // in this example we are receiving and responding with strings
 
 @main
-struct MyLambda: LambdaHandler {
-    typealias Event = String
-    typealias Output = String
-
-    init(context: LambdaInitializationContext) async throws {
-        // setup your resources that you want to reuse for every invocation here.
-    }
-
+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/Echo/Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.5
+// swift-tools-version:5.7
 
 import PackageDescription
 

Examples/ErrorHandling/Lambda.swift

@@ -17,12 +17,7 @@ import AWSLambdaRuntime
 // MARK: - Run Lambda
 
 @main
-struct MyLambda: LambdaHandler {
-    typealias Event = Request
-    typealias Output = Response
-
-    init(context: LambdaInitializationContext) async throws {}
-
+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/ErrorHandling/Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.5
+// swift-tools-version:5.7
 
 import PackageDescription
 

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 {