Readded state check for Lifecycle. Assert start happens in correct loop.

Author: fabianfett

Sources/AWSLambdaRuntimeCore/LambdaLifecycle.swift

@@ -27,7 +27,11 @@ extension Lambda {
         private let configuration: Configuration
         private let factory: HandlerFactory
 
-        private var state = State.idle
+        private var state = State.idle {
+            willSet {
+                precondition(newValue.order > state.order, "invalid state \(newValue) after \(state.order)")
+            }
+        }
 
         /// Create a new `Lifecycle`.
         ///
@@ -62,8 +66,12 @@ extension Lambda {
 
         /// Start the `Lifecycle`.
         ///
-        /// - Returns: An `EventLoopFuture` that is fulfilled after the Lambda hander has been created and initiliazed, and a first run has been schduled.
+        /// - Returns: An `EventLoopFuture` that is fulfilled after the Lambda hander has been created and initiliazed, and a first run has been scheduled.
+        /// 
+        /// - note: This method must be called  on the `EventLoop` the `Lifecycle` has been initialized with.
         public func start() -> EventLoopFuture<Void> {
+            assert(self.eventLoop.inEventLoop, "Start must be called on the `EventLoop` the `Lifecycle` has been initialized with.")
+            
             logger.info("lambda lifecycle starting with \(self.configuration)")
             self.state = .initializing
             // triggered when the Lambda has finished its last run

Tests/AWSLambdaRuntimeCoreTests/LambdaTest.swift

@@ -145,12 +145,19 @@ class LambdaTest: XCTestCase {
         }
         let result = Lambda.run(configuration: configuration, factory: { $0.makeSucceededFuture(EchoHandler()) })
 
-        guard case .success(let invocationCount) = result else {
-            return XCTFail("expected to have not failed")
+        switch result {
+        case .success(let invocationCount):
+            // this is an allowed outcome. the lambda was cancelled while it was processing a task.
+            // therefore: it was shut down before asking for a new invocation
+            XCTAssertGreaterThan(invocationCount, 0, "should have stopped before any request made")
+            XCTAssertLessThan(invocationCount, maxTimes, "should have stopped before \(maxTimes)")
+        case .failure(HTTPClient.Errors.cancelled):
+            // this is an allowed outcome. while the lambda was asking for a new invocation it was
+            // cancelled. for this reason the get new invocation request failed with .cancelled.
+            break
+        case .failure(let error):
+            XCTFail("Unexpected error: \(error)")
         }
-
-        XCTAssertGreaterThan(invocationCount, 0, "should have stopped before any request made")
-        XCTAssertLessThan(invocationCount, maxTimes, "should have stopped before \(maxTimes)")
     }
 
     func testTimeout() {