[vm/io] Fix an exception when attempting to immediately cancel socket…

… connection.

Fixes dartbug.com/45047

Change-Id: Ie4630684722e8c17cbc3766f91111b2a76bce7c1
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/186641
Commit-Queue: Alexander Aprelev <[email protected]>
Reviewed-by: Siva Annamalai <[email protected]>

runtime/tests/vm/dart/regress45047_test.dart

@@ -0,0 +1,23 @@
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Verify that socket connection gracefully closes if cancelled.
+
+import 'dart:async';
+import 'dart:io';
+
+import 'package:expect/expect.dart';
+
+void main() async {
+  final task = await Socket.startConnect('google.com', 80);
+  task.cancel();
+  try {
+    await task.socket;
+  } catch (e) {
+    Expect.isTrue(e is SocketException);
+    final socketException = e as SocketException;
+    Expect.isTrue(
+        socketException.message.startsWith('Connection attempt cancelled'));
+  }
+}

runtime/tests/vm/dart_2/regress45047_test.dart

@@ -0,0 +1,23 @@
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Verify that socket connection gracefully closes if cancelled.
+
+import 'dart:async';
+import 'dart:io';
+
+import 'package:expect/expect.dart';
+
+void main() async {
+  final task = await Socket.startConnect('google.com', 80);
+  task.cancel();
+  try {
+    await task.socket;
+  } catch (e) {
+    Expect.isTrue(e is SocketException);
+    final socketException = e as SocketException;
+    Expect.isTrue(
+        socketException.message.startsWith('Connection attempt cancelled'));
+  }
+}

sdk/lib/_internal/vm/bin/socket_patch.dart

@@ -844,7 +844,10 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
         }
         connecting.clear();
         addressesSubscription.cancel();
-        result.complete(socket);
+        if (!result.isCompleted) {
+          // Might be already completed via onCancel
+          result.complete(socket);
+        }
       }, error: (e, st) {
         connecting.remove(socket);
         socket.close();
@@ -864,6 +867,7 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
         s.setHandlers();
         s.setListening(read: false, write: false);
       }
+      addressesSubscription.cancel();
       connecting.clear();
       if (!result.isCompleted) {
         error ??= createError(