raise exception on setting TRestServer.OnNotifyCallback twice

- previous behavior was to allow several WS servers on the same TRestServer instance, silently disabling the precedent WS servers

Author: Arnaud Bouchez

src/mormot.commit.inc

@@ -1 +1 @@
-'2.0.4624'
+'2.0.4625'

src/rest/mormot.rest.http.server.pas

@@ -427,6 +427,8 @@   TRestHttpServer = class(TSynPersistent)
     // so that AJAX applications would be able to connect to this server
     // - this method raise an EHttpServer if the associated server class does not
     // support WebSockets, i.e. this instance isn't useBidirSocket/useBidirAsync
+    // - warning: only a single WebSockets server could be used in TRestServer
+    // callback at the same time to avoid confusion between the WS connections
     function WebSocketsEnable(
       const aWSURI, aWSEncryptionKey: RawUtf8; aWSAjax: boolean = false;
       aWSBinaryOptions: TWebSocketProtocolBinaryOptions = [pboSynLzCompress];
@@ -928,7 +930,7 @@ procedure TRestHttpServer.Shutdown(noRestServerShutdown: boolean);
         if not noRestServerShutdown then
           fDBServers[i].Server.Shutdown;
         if TMethod(fDBServers[i].Server.OnNotifyCallback).Data = self then
-          // avoid unexpected GPF
+          // avoid unexpected GPF, and proper TRestServer reuse
           fDBServers[i].Server.OnNotifyCallback := nil;
       end;
     finally

src/rest/mormot.rest.server.pas

@@ -1799,6 +1799,7 @@   TRestServer = class(TRest)
     fServer: IRestOrmServer;
     fRouter: TRestRouter;
     fRouterSafe: TRWLightLock;
+    fOnNotifyCallback: TOnRestServerClientCallback;
     procedure SetNoAjaxJson(const Value: boolean);
     function GetNoAjaxJson: boolean;
       {$ifdef HASINLINE}inline;{$endif}
@@ -1817,6 +1818,7 @@   TRestServer = class(TRest)
     function GetServiceMethodStat(const aMethod: RawUtf8): TSynMonitorInputOutput;
     procedure SetRoutingClass(aServicesRouting: TRestServerUriContextClass);
     procedure SetOptions(rso: TRestServerOptions);
+    procedure SetOnNotifyCallback(const event: TOnRestServerClientCallback);
     /// add a new session to the internal session list
     // - do not use this method directly: this callback is to be used by
     // TRestServerAuthentication* classes
@@ -1868,10 +1870,6 @@   TRestServer = class(TRest)
     // - Ctxt is nil if the session is closed due to a timeout
     // - Ctxt is not nil if the session is closed explicitly by the client
     OnSessionClosed: TOnOrmSession;
-    /// this event will be executed to push notifications from the server to
-    // a remote client, using a (fake) interface parameter
-    // - is nil by default, but may point e.g. to TRestHttpServer.NotifyCallback
-    OnNotifyCallback: TOnRestServerClientCallback;
     /// this event will be executed by TServiceFactoryServer.CreateInstance
     // - you may set a callback to customize a server-side service instance,
     // i.e. inject class-level dependencies:
@@ -1925,6 +1923,12 @@   TRestServer = class(TRest)
     // - is set by default to PAGINGPARAMETERS_YAHOO constant by
     // TRestServer.Create() constructor
     UriPagingParameters: TRestServerUriPagingParameters;
+    /// this event will be executed to push notifications from the WebSockets
+    // server to a remote client, using a (fake) interface parameter
+    // - is nil by default, but may point e.g. to TRestHttpServer.NotifyCallback
+    // - only a single WS server can be assigned to a TRestServer instance
+    property OnNotifyCallback: TOnRestServerClientCallback
+      read fOnNotifyCallback write SetOnNotifyCallback;
 
     /// Server initialization with a specified Database Model
     // - if HandleUserAuthentication is false, will set URI access rights to
@@ -6687,6 +6691,16 @@ function TRestServer.GetServiceMethodStat(
     result := nil;
 end;
 
+procedure TRestServer.SetOnNotifyCallback(const event: TOnRestServerClientCallback);
+begin
+  if Assigned(fOnNotifyCallback) and
+     Assigned(event) then
+    raise ERestException.CreateUtf8(
+      '%.OnNotifyCallback(%) set twice: only a single WS server can be assigned',
+      [self, ClassNameShort(TObject(TMethod(event).Data))^]);
+  fOnNotifyCallback := event;
+end;
+
 procedure TRestServer.SetRoutingClass(
   aServicesRouting: TRestServerUriContextClass);
 begin