Allow additional headers for WebSocket connect

sdk/lib/io/websocket_impl.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 const String _webSocketGUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
 
 // Matches _WebSocketOpcode.
 class _WebSocketMessageType {
@@ skipping 751 matching lines @@
   Duration _pingInterval;
   Timer _pingTimer;
   _WebSocketConsumer _consumer;
 
   int _outCloseCode;
   String _outCloseReason;
   Timer _closeTimer;
 
   static final HttpClient _httpClient = new HttpClient();
 
-  static Future<WebSocket> connect(String url, List<String> protocols) {
+  static Future<WebSocket> connect(
+      String url, List<String> protocols, Function onRequest) {
     Uri uri = Uri.parse(url);
     if (uri.scheme != "ws" && uri.scheme != "wss") {
       throw new WebSocketException("Unsupported URL scheme '${uri.scheme}'");
     }
     if (uri.userInfo != "") {
       throw new WebSocketException("Unsupported user info '${uri.userInfo}'");
     }
 
     Random random = new Random();
     // Generate 16 random bytes.
@@ skipping 10 matching lines @@
                   path: uri.path,
                   query: uri.query,
                   fragment: uri.fragment);
     return _httpClient.openUrl("GET", uri)
       .then((request) {
         // Setup the initial handshake.
         request.headers
             ..add(HttpHeaders.CONNECTION, "Upgrade")
             ..set(HttpHeaders.UPGRADE, "websocket")
             ..set("Sec-WebSocket-Key", nonce)
-            ..set("Cache-Control", "no-cache")

[kustermann, 2015/01/09 14:45:12]

Why was this removed?

[Søren Gjesse, 2015/01/12 15:36:34]

I thought it was not needed as a proxy should never cache the response to an
upgrade request. However that is of cause not always true, so added it back.

             ..set("Sec-WebSocket-Version", "13");
         if (protocols.isNotEmpty) {
           request.headers.add("Sec-WebSocket-Protocol", protocols);
         }
-        return request.close();
+        if (onRequest != null) {
+          var result = onRequest(request);
+          return result is Future

[Lasse Reichstein Nielsen, 2015/01/12 15:11:56]

Parentheses around (result is Future) expression (and generally around any
non-trivial condition expression, where trivial really means "without spaces")

[Søren Gjesse, 2015/01/12 15:36:34]

Dropped this code.

+              ? result.then((_) => request.close())
+              : request.close();
+        } else {
+          return request.close();
+        }

[Lasse Reichstein Nielsen, 2015/01/12 15:11:56]

Rewrite as:

if (onRequest != null) {
  var result = onRequest(request);  
  if (result is Future) {
    return result.then((_) => request.close());
  }
}
return request.close();


Is the code safe from memory leaks or similar if onRequest throws?

[Søren Gjesse, 2015/01/12 15:36:34]

Dropped this code.

       })
       .then((response) {
         void error(String message) {
           // Flush data.
           response.detachSocket().then((socket) {
             socket.destroy();
           });
           throw new WebSocketException(message);
         }
         if (response.statusCode != HttpStatus.SWITCHING_PROTOCOLS ||
@@ skipping 189 matching lines @@
            (code < WebSocketStatus.NORMAL_CLOSURE ||
             code == WebSocketStatus.RESERVED_1004 ||
             code == WebSocketStatus.NO_STATUS_RECEIVED ||
             code == WebSocketStatus.ABNORMAL_CLOSURE ||
             (code > WebSocketStatus.INTERNAL_SERVER_ERROR &&
              code < WebSocketStatus.RESERVED_1015) ||
             (code >= WebSocketStatus.RESERVED_1015 &&
              code < 3000));
   }
 }