LambdaCoding Changes and Tests (#8)

* Lint tests

* Make decode synchronous like other methods

* Make custom error message required

* Support error body customization

* Add helper for use with APIGatewayV2Requests

* Add coder tests and helpers

* Remove comment

* Fix possible test error

Author: mgacy

Package.swift

@@ -18,18 +18,10 @@ let package = Package(
         .package(url: "https://github.com/apple/swift-nio.git", .upToNextMajor(from: "2.43.1")),
         .package(url: "https://github.com/swift-server/swift-aws-lambda-events.git", branch: "main"),
         .package(url: "https://github.com/swift-server/swift-aws-lambda-runtime.git", branch: "main")
-    ],
-    targets: [
-        .testTarget(
-            name: "LambdaExtrasTests",
-            dependencies: [
-                "LambdaExtras"
-            ]
-        )
     ]
 )
 
-let genericTargets: [Target] = [
+let targets: [Target] = [
     .target(
         name: "LambdaExtrasCore",
         dependencies: [
@@ -50,14 +42,21 @@ let genericTargets: [Target] = [
         dependencies: [
             "LambdaExtrasCore"
         ]
+    ),
+    .testTarget(
+        name: "LambdaExtrasTests",
+        dependencies: [
+            "LambdaExtras",
+            "LambdaMocks"
+        ]
     )
 ]
 
 #if os(macOS)
 package.dependencies.append(.package(url: "https://github.com/realm/SwiftLint.git", exact: "0.54.0"))
-for target in genericTargets {
+for target in targets {
     target.plugins = [.plugin(name: "SwiftLintPlugin", package: "SwiftLint")]
 }
 #endif
 
-package.targets.append(contentsOf: genericTargets)
+package.targets = targets

Sources/LambdaExtras/APIGatewayCoder.swift

@@ -16,22 +16,28 @@ public struct APIGatewayCoder<E, O>: LambdaCoding where E: Codable, E: Sendable,
     let decoder: JSONDecoder
 
     /// A closure returning a response body from the given underlying output.
-    let responseBodyProvider: @Sendable (O) -> String?
+    let responseBodyProvider: @Sendable (O) throws -> String?
+
+    /// A closure returns a response body from the given error.
+    let errorBodyProvider: @Sendable (Error) throws -> String?
 
     /// Creates an instance.
     ///
     /// - Parameters:
     ///   - decoder: A JSON decoder.
     ///   - responseBody: A closure returning a response body from the given output.
+    ///   - errorBody: A closure returning a response body for the given error.
     public init(
         decoder: JSONDecoder = .init(),
-        responseBody: @escaping @Sendable (O) -> String? = { _ in nil }
+        responseBody: @escaping @Sendable (O) throws -> String? = { _ in nil },
+        errorBody: @escaping @Sendable (Error) throws -> String? = { $0.localizedDescription }
     ) {
         self.decoder = decoder
         self.responseBodyProvider = responseBody
+        self.errorBodyProvider = errorBody
     }
 
-    public func decode(event: APIGatewayV2Request) async throws -> E {
+    public func decode(event: APIGatewayV2Request) throws -> E {
         guard let body = event.body else {
             throw HandlerError.emptyBody
         }
@@ -42,42 +48,20 @@ public struct APIGatewayCoder<E, O>: LambdaCoding where E: Codable, E: Sendable,
     public func encode(output: O) throws -> APIGatewayV2Response {
         APIGatewayV2Response(
             statusCode: .ok,
-            body: responseBodyProvider(output))
+            body: try responseBodyProvider(output))
     }
 
     public func encode(error: Error) throws -> APIGatewayV2Response {
+        let statusCode: HTTPResponseStatus
         switch error {
         case HandlerError.emptyBody:
-            return APIGatewayV2Response(
-                statusCode: .badRequest,
-                body: errorResponseBody(error.localizedDescription))
-
-        case HandlerError.envError:
-            return APIGatewayV2Response(
-                statusCode: .internalServerError,
-                body: errorResponseBody(error.localizedDescription))
-
-        case HandlerError.custom(let message):
-            return APIGatewayV2Response(
-                statusCode: .internalServerError,
-                body: message.flatMap(errorResponseBody))
-
+            statusCode = .badRequest
         default:
-            return APIGatewayV2Response(
-                statusCode: .internalServerError,
-                body: errorResponseBody(error.localizedDescription))
+            statusCode = .internalServerError
         }
-    }
-}
 
-private extension APIGatewayCoder {
-    /// Returns a response body for the given error.
-    ///
-    /// - Parameter message: The error message
-    /// - Returns: The response body.
-    private func errorResponseBody(_ message: String) -> String {
-        """
-        {"reason": "\(message)"}
-        """
+        return APIGatewayV2Response(
+            statusCode: statusCode,
+            body: try errorBodyProvider(error.localizedDescription))
     }
 }

Sources/LambdaExtrasCore/Extensions.swift

@@ -51,6 +51,21 @@ public extension JSONDecoder {
     }
 }
 
+public extension JSONSerialization {
+    /// Returns an escaped string for the given JSON object data.
+    ///
+    /// - Parameters:
+    ///   - jsonData: The data from which to generate the JSON string.
+    ///   - options: Options for creating the JSON data.
+    /// - Returns: An escaped string representation of the given object `jsonData`.
+    static func escapedString(with jsonData: Data, options: WritingOptions = []) throws -> String {
+        let jsonString = String(decoding: jsonData, as: UTF8.self)
+        let data = try data(withJSONObject: [jsonString], options: options)
+        let encodedString = String(decoding: data, as: UTF8.self)
+        return String(encodedString.dropLast().dropFirst())
+    }
+}
+
 public extension Optional {
     /// Convienence method to `throw` if an optional type has a `nil` value.
     ///

Sources/LambdaExtrasCore/HandlerError.swift

@@ -14,7 +14,7 @@ public enum HandlerError: Error, Equatable, LocalizedError {
     /// The lambda context is missing an expected environment variable.
     case envError(String)
     /// A custom error.
-    case custom(_ message: String?)
+    case custom(_ message: String)
 
     /// Retrieve the description for this error.
     public var errorDescription: String? {
@@ -24,7 +24,7 @@ public enum HandlerError: Error, Equatable, LocalizedError {
         case .envError(let variable):
             return "The environment does not contain the expected variable `\(variable)`."
         case .custom(let message):
-            return message ?? "Unknown error."
+            return message
         }
     }
 }

Sources/LambdaExtrasCore/Protocols/LambdaCoding.swift

@@ -25,7 +25,7 @@ public protocol LambdaCoding<Event, Output, UnderlyingEvent, UnderlyingOutput> {
     ///
     /// - Parameter event: The event to encode.
     /// - Returns: An underlying event.
-    func decode(event: Event) async throws -> UnderlyingEvent
+    func decode(event: Event) throws -> UnderlyingEvent
 
     /// Encodes the given output to that of a lambda.
     ///