Set server receiver to initialized at the end of the initialize r…

…equest (#589)

src/Server/LanguageServer.cs

@@ -313,10 +313,15 @@ await LanguageProtocolEventingHelper.Run(
             ).ConfigureAwait(false);
 
 
+            // Allow the server receiver to start processing incoming notifications and requests. It
+            // is necessary to do this now, and not in the Initialized handler, because otherwise
+            // clients can enter a race with the receiver and have their notifications and requests
+            // erroneously dropped.
+            _serverReceiver.Initialized();
+
             // TODO:
             if (_clientVersion == ClientVersion.Lsp2)
             {
-                _serverReceiver.Initialized();
                 _initializeComplete.OnNext(result);
                 _initializeComplete.OnCompleted();
             }
@@ -328,7 +333,6 @@ public Task<Unit> Handle(InitializedParams @params, CancellationToken token)
         {
             if (_clientVersion == ClientVersion.Lsp3)
             {
-                _serverReceiver.Initialized();
                 _initializeComplete.OnNext(ServerSettings);
                 _initializeComplete.OnCompleted();
             }