Fix fixmes: fail task when client is shutdown

Author: PopFlamingo

Sources/AsyncHTTPClient/ConnectionPool.swift

@@ -404,7 +404,6 @@ class ConnectionPool {
             }
         }
 
-        // FIXME: Should this be a precondition or an assertion?
         private func preconditionIsOpened() {
             self.stateLock.withLock {
                 precondition(self.state.isClosed == false, "Attempting to use closed HTTP1ConnectionProvider")

Sources/AsyncHTTPClient/HTTPClient.swift

@@ -262,16 +262,6 @@ public class HTTPClient {
                                                               delegate: Delegate,
                                                               eventLoop eventLoopPreference: EventLoopPreference,
                                                               deadline: NIODeadline? = nil) -> Task<Delegate.Response> {
-        // FIXME: Is this correct to assert?
-        self.stateLock.withLock {
-            switch state {
-            case .upAndRunning:
-                break
-            case .shuttingDown, .shutDown:
-                assertionFailure("Attempting to execute a request on shutdown client")
-            }
-        }
-
         let taskEL: EventLoop
         switch eventLoopPreference.preference {
         case .indifferent:
@@ -286,6 +276,19 @@ public class HTTPClient {
             taskEL = delegateEL
         }
 
+        let failedTask: Task<Delegate.Response>? = self.stateLock.withLock {
+            switch state {
+            case .upAndRunning:
+                return nil
+            case .shuttingDown, .shutDown:
+                return Task<Delegate.Response>.failedTask(eventLoop: taskEL, error: HTTPClientError.alreadyShutdown)
+            }
+        }
+
+        if let failedTask = failedTask {
+            return failedTask
+        }
+
         let redirectHandler: RedirectHandler<Delegate.Response>?
         switch self.configuration.redirectConfiguration.configuration {
         case .follow(let max, let allowCycles):

Sources/AsyncHTTPClient/HTTPHandler.swift

@@ -498,6 +498,12 @@ extension HTTPClient {
             self.lock = Lock()
         }
 
+        static func failedTask(eventLoop: EventLoop, error: Error) -> Task<Response> {
+            let task = self.init(eventLoop: eventLoop)
+            task.promise.fail(error)
+            return task
+        }
+
         /// `EventLoopFuture` for the response returned by this request.
         public var futureResult: EventLoopFuture<Response> {
             return self.promise.futureResult
@@ -564,7 +570,9 @@ extension HTTPClient {
                 }
 
             } else {
-                // TODO: This is only reached in some internal unit t
+                // TODO: This seems only reached in some internal unit test
+                // Maybe there could be a better handling in the future to make
+                // it an error outside of testing contexts
                 return self.eventLoop.makeSucceededFuture(())
             }
         }