Fix crash if request is canceled after request header is send

Author: dnadoba

Sources/AsyncHTTPClient/ConnectionPool/HTTP1/HTTP1ClientChannelHandler.swift

@@ -186,10 +186,14 @@ final class HTTP1ClientChannelHandler: ChannelDuplexHandler {
         case .sendRequestHead(let head, let sendEnd):
             self.sendRequestHead(head, sendEnd: sendEnd, context: context)
         case .notifyRequestHeadSendSuccessfully(let resumeRequestBodyStream, let startIdleTimer):
-
+            // We can force unwrap the request here, as we have just validated in the state machine,
+            // that the request is neither failed nor finished yet
             self.request!.requestHeadSent()
-            if resumeRequestBodyStream {
-                self.request!.resumeRequestBodyStream()
+            if resumeRequestBodyStream, let request = self.request {
+                // The above request head send notification might lead the request to mark itself as
+                // cancelled, which in turn might pop the request of the handler. For this reason we
+                // must check if the request is still present here.
+                request.resumeRequestBodyStream()
             }
             if startIdleTimer {
                 if let timeoutAction = self.idleReadTimeoutStateMachine?.requestEndSent() {

Sources/AsyncHTTPClient/ConnectionPool/HTTP2/HTTP2ClientRequestHandler.swift

@@ -143,9 +143,14 @@ final class HTTP2ClientRequestHandler: ChannelDuplexHandler {
         case .sendRequestHead(let head, let sendEnd):
             self.sendRequestHead(head, sendEnd: sendEnd, context: context)
         case .notifyRequestHeadSendSuccessfully(let resumeRequestBodyStream, let startIdleTimer):
+            // We can force unwrap the request here, as we have just validated in the state machine,
+            // that the request is neither failed nor finished yet
             self.request!.requestHeadSent()
-            if resumeRequestBodyStream {
-                self.request!.resumeRequestBodyStream()
+            if resumeRequestBodyStream, let request = self.request {
+                // The above request head send notification might lead the request to mark itself as
+                // cancelled, which in turn might pop the request of the handler. For this reason we
+                // must check if the request is still present here.
+                request.resumeRequestBodyStream()
             }
             if startIdleTimer {
                 if let timeoutAction = self.idleReadTimeoutStateMachine?.requestEndSent() {

Tests/AsyncHTTPClientTests/HTTPClientTests.swift

@@ -3405,4 +3405,36 @@ final class HTTPClientTests: XCTestCaseHTTPClientTestsBaseClass {
 
         XCTAssertNoThrow(try client.execute(request: request).wait())
     }
+    
+    func testCancelingHTTP1RequestAfterHeaderSend() throws {
+        var request = try HTTPClient.Request(url: self.defaultHTTPBin.baseURL + "/wait", method: .POST)
+        // non-empty body is important
+        request.body = .byteBuffer(ByteBuffer([1]))
+        
+        class CancelAfterHeadSend: HTTPClientResponseDelegate {
+            init() {}
+            func didFinishRequest(task: AsyncHTTPClient.HTTPClient.Task<Void>) throws -> Void { }
+            func didSendRequestHead(task: HTTPClient.Task<Void>, _ head: HTTPRequestHead) {
+                task.cancel()
+            }
+        }
+        XCTAssertThrowsError(try defaultClient.execute(request: request, delegate: CancelAfterHeadSend()).wait())
+    }
+    
+    func testCancelingHTTP2RequestAfterHeaderSend() throws {
+        let bin = HTTPBin(.http2())
+        defer { XCTAssertNoThrow(try bin.shutdown()) }
+        var request = try HTTPClient.Request(url: bin.baseURL + "/wait", method: .POST)
+        // non-empty body is important
+        request.body = .byteBuffer(ByteBuffer([1]))
+        
+        class CancelAfterHeadSend: HTTPClientResponseDelegate {
+            init() {}
+            func didFinishRequest(task: AsyncHTTPClient.HTTPClient.Task<Void>) throws -> Void { }
+            func didSendRequestHead(task: HTTPClient.Task<Void>, _ head: HTTPRequestHead) {
+                task.cancel()
+            }
+        }
+        XCTAssertThrowsError(try defaultClient.execute(request: request, delegate: CancelAfterHeadSend()).wait())
+    }
 }