[io] Correct websocket close code upon abnormal closure

TEST=tests/standalone/io/web_socket_abnormal_close_test.dart

[email protected]

Bug: #60217
Change-Id: I6168abfa9fc0228f98b97f7873449970f59f1a30
Fixes #60217
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/413140
Commit-Queue: Martin Kustermann <[email protected]>
Reviewed-by: Martin Kustermann <[email protected]>
Auto-Submit: Mylo Fawcett <[email protected]>
Reviewed-by: Slava Egorov <[email protected]>

Author: abitofevrything

sdk/lib/_http/http_testing.dart

@@ -37,6 +37,7 @@ part of dart._http;
 typedef TestingClass$_Cookie = _Cookie;
 typedef TestingClass$_HttpHeaders = _HttpHeaders;
 typedef TestingClass$_HttpParser = _HttpParser;
+typedef TestingClass$_HttpRequest = _HttpRequest;
 typedef TestingClass$_SHA1 = _SHA1;
 typedef TestingClass$_WebSocketProtocolTransformer =
     _WebSocketProtocolTransformer;
@@ -52,6 +53,14 @@ extension Testing$_HttpHeaders on _HttpHeaders {
   List<Cookie> test$_parseCookies() => this._parseCookies();
 }
 
+extension Testing$_HttpRequest on _HttpRequest {
+  _HttpConnection get test$_httpConnection => _httpConnection;
+}
+
+extension Testing$_HttpConnection on _HttpConnection {
+  Socket get test$_socket => _socket;
+}
+
 extension Testing$_WebSocketProtocolTransformer
     on _WebSocketProtocolTransformer {
   int get test$_state => this._state;

sdk/lib/_http/websocket_impl.dart

@@ -89,7 +89,7 @@ class _WebSocketProtocolTransformer
   int _remainingPayloadBytes = -1;
   int _unmaskingIndex = 0;
   int _currentMessageType = _WebSocketMessageType.NONE;
-  int closeCode = WebSocketStatus.noStatusReceived;
+  int closeCode = WebSocketStatus.abnormalClosure;
   String closeReason = "";
 
   EventSink<dynamic /*List<int>|_WebSocketPing|_WebSocketPong*/>? _eventSink;
@@ -316,6 +316,7 @@ class _WebSocketProtocolTransformer
         switch (_opcode) {
           case _WebSocketOpcode.CLOSE:
             _state = CLOSED;
+            closeCode = WebSocketStatus.noStatusReceived;
             _eventSink!.close();
             break;
           case _WebSocketOpcode.PING:

tests/standalone/io/web_socket_abnormal_close_test.dart

@@ -0,0 +1,54 @@
+// Copyright (c) 2025, 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 the close code for an abnormally closed WebSocket is 1006
+// (WebSocketStatus.abnormalClosure).
+//
+// See section 7.1.5 of RFC 6455:
+// If _The WebSocket Connection is Closed_ and no Close control frame was
+// received by the endpoint (such as could occur if the underlying transport
+// connection is lost), _The WebSocket Connection Close Code_ is considered to
+// be 1006.
+
+import 'dart:async';
+import 'dart:io';
+
+// ignore: IMPORT_INTERNAL_LIBRARY
+import "dart:_http"
+    show
+        TestingClass$_HttpRequest,
+        Testing$_HttpRequest,
+        Testing$_HttpConnection;
+
+import "package:expect/async_helper.dart";
+import 'package:expect/expect.dart';
+
+typedef _HttpRequest = TestingClass$_HttpRequest;
+
+void main() {
+  asyncStart();
+
+  HttpRequest closeSocketAfterDelay(HttpRequest request) {
+    Expect.type<_HttpRequest>(request);
+
+    Timer(Duration(seconds: 1), () {
+      (request as _HttpRequest).test$_httpConnection.test$_socket.destroy();
+    });
+
+    return request;
+  }
+
+  HttpServer.bind('localhost', 0).then((server) {
+    server.map(closeSocketAfterDelay).transform(WebSocketTransformer()).drain();
+
+    WebSocket.connect('ws://localhost:${server.port}').then((ws) {
+      ws.drain().then((_) {
+        Expect.equals(ws.closeCode, WebSocketStatus.abnormalClosure);
+
+        server.close();
+        asyncEnd();
+      });
+    });
+  });
+}