[io/socket] When socket connection fails report stacktrace of the callsite.

Currently stack trace reported on thrown exceptions is null.

TEST=socket_connect_stacktrace_test.dart

Bug: https://github.com/dart-lang/sdk/issues/44994
Change-Id: I188aff197ab519272f63f41387b94458c2f1cec7
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/202802
Reviewed-by: Zach Anderson <zra@google.com>
Commit-Queue: Alexander Aprelev <aam@google.com>

sdk/lib/_http/http_impl.dart

@@ -2796,8 +2796,8 @@ class _HttpClient implements HttpClient {
       _HttpProfileData? profileData) {
     Iterator<_Proxy> proxies = proxyConf.proxies.iterator;
 
-    Future<_ConnectionInfo> connect(error) {
-      if (!proxies.moveNext()) return new Future.error(error);
+    Future<_ConnectionInfo> connect(error, stackTrace) {
+      if (!proxies.moveNext()) return new Future.error(error, stackTrace);
       _Proxy proxy = proxies.current;
       String host = proxy.isDirect ? uriHost : proxy.host!;
       int port = proxy.isDirect ? uriPort : proxy.port!;
@@ -2807,7 +2807,7 @@ class _HttpClient implements HttpClient {
           .catchError(connect);
     }
 
-    return connect(new HttpException("No proxies given"));
+    return connect(new HttpException("No proxies given"), StackTrace.current);
   }
 
   _SiteCredentials? _findCredentials(Uri url, [_AuthenticationScheme? scheme]) {

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

@@ -673,10 +673,13 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
             "Must be a string or native InternetAddress");
       }
     }
+
+    final stackTrace = StackTrace.current;
+
     return new Future.value(host).then<ConnectionTask<_NativeSocket>>((host) {
       if (host is _InternetAddress) {
-        return tryConnectToResolvedAddresses(
-            host, port, source, Stream.value(<_InternetAddress>[host]));
+        return tryConnectToResolvedAddresses(host, port, source,
+            Stream.value(<_InternetAddress>[host]), stackTrace);
       }
       final hostname = host as String;
       final staggeredLookupOverride = bool.fromEnvironment(
@@ -692,7 +695,8 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
               ? staggeredLookup(hostname)
               : lookupAsStream(hostname);
 
-      return tryConnectToResolvedAddresses(host, port, source, stream);
+      return tryConnectToResolvedAddresses(
+          host, port, source, stream, stackTrace);
     });
   }
 
@@ -700,7 +704,8 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
       dynamic host,
       int port,
       _InternetAddress? source,
-      Stream<List<InternetAddress>> addresses) {
+      Stream<List<InternetAddress>> addresses,
+      StackTrace callerStackTrace) {
     // Completer for result.
     final result = new Completer<_NativeSocket>();
     // Error, set if an error occurs.
@@ -780,7 +785,7 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
         assert(error != null);
         if (!result.isCompleted) {
           // Might be already completed via onCancel
-          result.completeError(error);
+          result.completeError(error, callerStackTrace);
         }
         return;
       }
@@ -884,7 +889,7 @@ class _NativeSocket extends _NativeSocketNativeWrapper with _ServiceObject {
       if (!result.isCompleted) {
         error ??= createError(
             null, "Connection attempt cancelled, host: ${host}, port: ${port}");
-        result.completeError(error);
+        result.completeError(error, callerStackTrace);
       }
     }
 

tests/standalone/io/socket_connect_stacktrace_test.dart

@@ -0,0 +1,32 @@
+// 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.
+//
+// Tests stack trace on socket exceptions.
+
+import "dart:async";
+import "dart:io";
+
+import "package:async_helper/async_helper.dart";
+import "package:expect/expect.dart";
+
+import 'dart:io';
+
+Future<void> main() async {
+  asyncStart();
+
+  // Test stacktrace when lookup fails
+  try {
+    await WebSocket.connect('ws://localhost.tld:0/ws');
+  } catch (err, stackTrace) {
+    Expect.contains("main ", stackTrace.toString());
+  }
+
+  // Test stacktrace when connection fails
+  try {
+    await WebSocket.connect('ws://localhost:0/ws');
+  } catch (err, stackTrace) {
+    Expect.contains("main ", stackTrace.toString());
+  }
+  asyncEnd();
+}

tests/standalone_2/io/socket_connect_stacktrace_test.dart

@@ -0,0 +1,32 @@
+// 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.
+//
+// Tests stack trace on socket exceptions.
+
+import "dart:async";
+import "dart:io";
+
+import "package:async_helper/async_helper.dart";
+import "package:expect/expect.dart";
+
+import 'dart:io';
+
+Future<void> main() async {
+  asyncStart();
+
+  // Test stacktrace when lookup fails
+  try {
+    await WebSocket.connect('ws://localhost.tld:0/ws');
+  } catch (err, stackTrace) {
+    Expect.contains("main ", stackTrace.toString());
+  }
+
+  // Test stacktrace when connection fails
+  try {
+    await WebSocket.connect('ws://localhost:0/ws');
+  } catch (err, stackTrace) {
+    Expect.contains("main ", stackTrace.toString());
+  }
+  asyncEnd();
+}