Fix bi directional streaming test

Tests/AsyncHTTPClientTests/HTTPClientTestUtils.swift

@@ -1149,23 +1149,157 @@ struct CollectEverythingLogHandler: LogHandler {
     }
 }
 
+/// A ``HTTPClientResponseDelegate`` that buffers the incoming response parts for the consumer. The consumer can
+/// consume the bytes by calling ``next()`` on the delegate.
+///
+/// The sole purpose of this class is to enable straight-line stream tests.
+class ResponseStreamDelegate: HTTPClientResponseDelegate {
+    typealias Response = Void
+
+    enum State {
+        /// The delegate is in the idle state. There are no http response parts to be buffered
+        /// and the consumer did not signal a demand. Transitions to all other states are allowed.
+        case idle
+        /// The consumer has signaled a demand for more bytes, but none where available. Can
+        /// transition to `.idle` (when new bytes arrive), `.finished` (when the stream finishes or fails)
+        case waitingForBytes(EventLoopPromise<ByteBuffer?>)
+        /// The consumer has signaled no further demand but bytes keep arriving. Valid transitions
+        /// to `.idle` (when bytes are consumed), `.finished` (when bytes are consumed, and the
+        /// stream has ended), `.failed` (if an error is forwarded)
+        case buffering(ByteBuffer, done: Bool)
+        /// Stores an error for consumption. Valid transitions are: `.finished`, when the error was consumed.
+        case failed(Error)
+        /// The stream has finished and all bytes or errors where consumed.
+        case finished
+    }
+
+    let eventLoop: EventLoop
+    private var state: State = .idle
+
+    init(eventLoop: EventLoop) {
+        self.eventLoop = eventLoop
+    }
+
+    func next() -> EventLoopFuture<ByteBuffer?> {
+        if self.eventLoop.inEventLoop {
+            return self.next0()
+        } else {
+            return self.eventLoop.flatSubmit {
+                self.next0()
+            }
+        }
+    }
+
+    private func next0() -> EventLoopFuture<ByteBuffer?> {
+        switch self.state {
+        case .idle:
+            let promise = self.eventLoop.makePromise(of: ByteBuffer?.self)
+            self.state = .waitingForBytes(promise)
+            return promise.futureResult
+
+        case .buffering(let byteBuffer, done: false):
+            self.state = .idle
+            return self.eventLoop.makeSucceededFuture(byteBuffer)
+
+        case .buffering(let byteBuffer, done: true):
+            self.state = .finished
+            return self.eventLoop.makeSucceededFuture(byteBuffer)
+
+        case .waitingForBytes:
+            preconditionFailure("Don't call `.next` twice")
+
+        case .failed(let error):
+            self.state = .finished
+            return self.eventLoop.makeFailedFuture(error)
+
+        case .finished:
+            return self.eventLoop.makeSucceededFuture(nil)
+        }
+    }
+
+    // MARK: HTTPClientResponseDelegate
+
+    func didSendRequestHead(task: HTTPClient.Task<Response>, _ head: HTTPRequestHead) {
+        self.eventLoop.preconditionInEventLoop()
+    }
+
+    func didSendRequestPart(task: HTTPClient.Task<Response>, _ part: IOData) {
+        self.eventLoop.preconditionInEventLoop()
+    }
+
+    func didSendRequest(task: HTTPClient.Task<Response>) {
+        self.eventLoop.preconditionInEventLoop()
+    }
+
+    func didReceiveHead(task: HTTPClient.Task<Response>, _ head: HTTPResponseHead) -> EventLoopFuture<Void> {
+        self.eventLoop.preconditionInEventLoop()
+        return task.eventLoop.makeSucceededVoidFuture()
+    }
+
+    func didReceiveBodyPart(task: HTTPClient.Task<Response>, _ buffer: ByteBuffer) -> EventLoopFuture<Void> {
+        self.eventLoop.preconditionInEventLoop()
+
+        switch self.state {
+        case .idle:
+            self.state = .buffering(buffer, done: false)
+        case .waitingForBytes(let promise):
+            self.state = .idle
+            promise.succeed(buffer)
+        case .buffering(var byteBuffer, done: false):
+            var buffer = buffer
+            byteBuffer.writeBuffer(&buffer)
+            self.state = .buffering(byteBuffer, done: false)
+        case .buffering(_, done: true), .finished, .failed:
+            preconditionFailure("Invalid state: \(self.state)")
+        }
+
+        return task.eventLoop.makeSucceededVoidFuture()
+    }
+
+    func didReceiveError(task: HTTPClient.Task<Response>, _ error: Error) {
+        self.eventLoop.preconditionInEventLoop()
+
+        switch self.state {
+        case .idle:
+            self.state = .failed(error)
+        case .waitingForBytes(let promise):
+            self.state = .finished
+            promise.fail(error)
+        case .buffering(_, done: false):
+            self.state = .failed(error)
+        case .buffering(_, done: true), .finished, .failed:
+            preconditionFailure("Invalid state: \(self.state)")
+        }
+    }
+
+    func didFinishRequest(task: HTTPClient.Task<Response>) throws {
+        self.eventLoop.preconditionInEventLoop()
+
+        switch self.state {
+        case .idle:
+            self.state = .finished
+        case .waitingForBytes(let promise):
+            self.state = .finished
+            promise.succeed(nil)
+        case .buffering(let byteBuffer, done: false):
+            self.state = .buffering(byteBuffer, done: true)
+        case .buffering(_, done: true), .finished, .failed:
+            preconditionFailure("Invalid state: \(self.state)")
+        }
+    }
+}
+
 class HTTPEchoHandler: ChannelInboundHandler {
     typealias InboundIn = HTTPServerRequestPart
     typealias OutboundOut = HTTPServerResponsePart
 
-    var promises: CircularBuffer<EventLoopPromise<Void>> = CircularBuffer()
-
     func channelRead(context: ChannelHandlerContext, data: NIOAny) {
         let request = self.unwrapInboundIn(data)
         switch request {
         case .head:
-            context.writeAndFlush(self.wrapOutboundOut(.head(.init(version: .init(major: 1, minor: 1), status: .ok))), promise: nil)
+            context.writeAndFlush(self.wrapOutboundOut(.head(.init(version: .http1_1, status: .ok))), promise: nil)
         case .body(let bytes):
-            context.writeAndFlush(self.wrapOutboundOut(.body(.byteBuffer(bytes)))).whenSuccess {
-                if let promise = self.promises.popFirst() {
-                    promise.succeed(())
-                }
-            }
+            context.writeAndFlush(self.wrapOutboundOut(.body(.byteBuffer(bytes))), promise: nil)
         case .end:
             context.writeAndFlush(self.wrapOutboundOut(.end(nil)), promise: nil)
             context.close(promise: nil)

Tests/AsyncHTTPClientTests/HTTPClientTests.swift

@@ -2815,40 +2815,67 @@ class HTTPClientTests: XCTestCase {
         XCTAssertEqual(result, .success, "we never closed the connection!")
     }
 
-    func testBiDirectionalStreaming() throws {
-        let handler = HTTPEchoHandler()
+    // In this test, we test that a request can continue to stream its body after the response head,
+    // was received. The client sends a number to the server and waits for the server to echo the
+    // number. Once the client receives the echoed number, it will continue with the next number.
+    // The client and server ping/pong 30 times.
+    func testBiDirectionalStreaming() {
+        let httpBin = HTTPBin(.http1_1(ssl: false, compress: false)) { _ in HTTPEchoHandler() }
+        defer { XCTAssertNoThrow(try httpBin.shutdown()) }
 
-        let server = try ServerBootstrap(group: self.serverGroup)
-            .serverChannelOption(ChannelOptions.socketOption(.so_reuseaddr), value: 1)
-            .childChannelInitializer { channel in
-                channel.pipeline.configureHTTPServerPipeline().flatMap {
-                    channel.pipeline.addHandler(handler)
-                }
-            }
-            .bind(host: "localhost", port: 0)
-            .wait()
+        let eventLoopGroup = MultiThreadedEventLoopGroup(numberOfThreads: 2)
+        defer { XCTAssertNoThrow(try eventLoopGroup.syncShutdownGracefully()) }
+        let writeEL = eventLoopGroup.next()
+        let delegateEL = eventLoopGroup.next()
 
-        defer {
-            server.close(promise: nil)
-        }
+        let httpClient = HTTPClient(eventLoopGroupProvider: .shared(eventLoopGroup))
+        defer { XCTAssertNoThrow(try httpClient.syncShutdown()) }
+
+        let delegate = ResponseStreamDelegate(eventLoop: delegateEL)
 
         let body: HTTPClient.Body = .stream { writer in
-            let promise = self.clientGroup.next().makePromise(of: Void.self)
-            handler.promises.append(promise)
-            return writer.write(.byteBuffer(ByteBuffer(string: "hello"))).flatMap {
-                promise.futureResult
-            }.flatMap {
-                let promise = self.clientGroup.next().makePromise(of: Void.self)
-                handler.promises.append(promise)
-                return writer.write(.byteBuffer(ByteBuffer(string: "hello2"))).flatMap {
-                    promise.futureResult
+            let finalPromise = writeEL.makePromise(of: Void.self)
+
+            func writeLoop(_ writer: HTTPClient.Body.StreamWriter, index: Int) {
+                // always invoke from the wrong el to test thread safety
+                writeEL.preconditionInEventLoop()
+
+                if index >= 30 {
+                    return finalPromise.succeed(())
+                }
+
+                let sent = ByteBuffer(integer: index)
+                writer.write(.byteBuffer(sent)).flatMap { () -> EventLoopFuture<ByteBuffer?> in
+                    // ensure, that the writer dispatches back to the expected delegate el.
+                    delegateEL.preconditionInEventLoop()
+                    return delegate.next()
+                }.whenComplete { result in
+                    switch result {
+                    case .success(let returned):
+                        XCTAssertEqual(returned, sent)
+
+                        writeEL.execute {
+                            writeLoop(writer, index: index + 1)
+                        }
+
+                    case .failure(let error):
+                        finalPromise.fail(error)
+                    }
                 }
             }
+
+            writeEL.execute {
+                writeLoop(writer, index: 0)
+            }
+
+            return finalPromise.futureResult
         }
 
-        let future = self.defaultClient.execute(url: "http://localhost:\(server.localAddress!.port!)", body: body)
+        let request = try! HTTPClient.Request(url: "http://localhost:\(httpBin.port)", body: body)
+        let future = httpClient.execute(request: request, delegate: delegate, eventLoop: .delegate(on: delegateEL))
 
         XCTAssertNoThrow(try future.wait())
+        XCTAssertNil(try delegate.next().wait())
     }
 
     func testSynchronousHandshakeErrorReporting() throws {