WebSocket handshake response is deterministic on failure:

Add test for websocket handshake failure HTTP response

fix #2364
close #2365

include/boost/beast/websocket/impl/handshake.hpp

@@ -225,6 +225,9 @@ do_handshake(
     RequestDecorator const& decorator,
     error_code& ec)
 {
+    if(res_p)
+        res_p->result(http::status::internal_server_error);
+
     auto& impl = *impl_;
     impl.change_status(status::handshake);
     impl.reset();
@@ -275,12 +278,18 @@ do_handshake(
     if(impl.check_stop_now(ec))
         return;
 
-    impl.on_response(p.get(), key, ec);
-    if(impl.check_stop_now(ec))
-        return;
-
-    if(res_p)
+    if (res_p)
+    {
+        // If res_p is not null, move parser's response into it.
         *res_p = p.release();
+    }
+    else
+    {
+        // Otherwise point res_p at the response in the parser.
+        res_p = &p.get();
+    }
+
+    impl.on_response(*res_p, key, ec);
 }
 
 //------------------------------------------------------------------------------
@@ -325,6 +334,7 @@ async_handshake(
     detail::sec_ws_key_type key;
     auto req = impl_->build_request(
         key, host, target, &default_decorate_req);
+    res.result(http::status::internal_server_error);
     return net::async_initiate<
         HandshakeHandler,
         void(error_code)>(

include/boost/beast/websocket/stream.hpp

@@ -675,7 +675,11 @@ public:
 
         @param res The HTTP Upgrade response returned by the remote
         endpoint. The caller may use the response to access any
-        additional information sent by the server.
+        additional information sent by the server. Note that the response object
+        referenced by this parameter will be updated as long as the stream has
+        received a valid HTTP response. If not (for example because of a communications
+        error), the response contents will be undefined except for the result() which
+        will bet set to 500, Internal Server Error.
 
         @param host The name of the remote host. This is required by
         the HTTP protocol to set the "Host" header field.