Fix shellmap OrderManager use after dispose.

OpenRA.Game/Game.cs

@@ -84,7 +84,14 @@ namespace OpenRA
 
 		static void JoinInner(OrderManager om)
 		{
+			// HACK: The shellmap World and OrderManager are owned by the main menu's WorldRenderer instead of Game.
+			// This allows us to switch Game.OrderManager from the shellmap to the new network connection when joining
+			// a lobby, while keeping the OrderManager that runs the shellmap intact.
+			// A matching check in World.Dispose (which is called by WorldRenderer.Dispose) makes sure that we dispose
+			// the shellmap's OM when a lobby game actually starts.
+			if (OrderManager?.World == null || OrderManager.World.Type != WorldType.Shellmap)
 				OrderManager?.Dispose();
+
 			OrderManager = om;
 		}
 

OpenRA.Game/Network/Connection.cs

@@ -45,6 +45,7 @@ namespace OpenRA.Network
 		readonly Queue<(int Frame, int SyncHash, ulong DefeatState)> sync = new Queue<(int, int, ulong)>();
 		readonly Queue<(int Frame, OrderPacket Orders)> orders = new Queue<(int, OrderPacket)>();
 		readonly Queue<OrderPacket> immediateOrders = new Queue<OrderPacket>();
+		bool disposed;
 
 		int IConnection.LocalClientId => LocalClientId;
 
@@ -72,8 +73,15 @@ namespace OpenRA.Network
 		void IConnection.Receive(OrderManager orderManager)
 		{
 			while (immediateOrders.TryDequeue(out var i))
+			{
 				orderManager.ReceiveImmediateOrders(LocalClientId, i);
 
+				// An immediate order may trigger a chain of actions that disposes the OrderManager and connection.
+				// Bail out to avoid potential problems from acting on disposed objects.
+				if (disposed)
+					break;
+			}
+
 			// Project orders forward to the next frame
 			while (orders.TryDequeue(out var o))
 				orderManager.ReceiveOrders(LocalClientId, (o.Frame + 1, o.Orders));
@@ -82,7 +90,10 @@ namespace OpenRA.Network
 				orderManager.ReceiveSync(s);
 		}
 
-		void IDisposable.Dispose() { }
+		void IDisposable.Dispose()
+		{
+			disposed = true;
+		}
 	}
 
 	public sealed class NetworkConnection : IConnection
@@ -272,6 +283,11 @@ namespace OpenRA.Network
 			{
 				orderManager.ReceiveImmediateOrders(clientId, i);
 				Recorder?.Receive(clientId, i.Serialize(0));
+
+				// An immediate order may trigger a chain of actions that disposes the OrderManager and connection.
+				// Bail out to avoid potential problems from acting on disposed objects.
+				if (disposed)
+					return;
 			}
 
 			while (sentSync.TryDequeue(out var s))
@@ -312,6 +328,11 @@ namespace OpenRA.Network
 
 				if (record)
 					Recorder?.Receive(p.FromClient, p.Data);
+
+				// An immediate order may trigger a chain of actions that disposes the OrderManager and connection.
+				// Bail out to avoid potential problems from acting on disposed objects.
+				if (disposed)
+					return;
 			}
 		}
 

OpenRA.Game/Network/OrderManager.cs

@@ -128,19 +128,11 @@ namespace OpenRA.Network
 
 		public void ReceiveDisconnect(int clientIndex)
 		{
-			// HACK: The shellmap relies on ticking a disposed OM
-			if (disposed && World.Type != WorldType.Shellmap)
-				return;
-
 			pendingOrders.Remove(clientIndex);
 		}
 
 		public void ReceiveSync((int Frame, int SyncHash, ulong DefeatState) sync)
 		{
-			// HACK: The shellmap relies on ticking a disposed OM
-			if (disposed && World.Type != WorldType.Shellmap)
-				return;
-
 			if (syncForFrame.TryGetValue(sync.Frame, out var s))
 			{
 				if (s.SyncHash != sync.SyncHash || s.DefeatState != sync.DefeatState)
@@ -152,10 +144,6 @@ namespace OpenRA.Network
 
 		public void ReceiveImmediateOrders(int clientId, OrderPacket orders)
 		{
-			// HACK: The shellmap relies on ticking a disposed OM
-			if (disposed && World.Type != WorldType.Shellmap)
-				return;
-
 			foreach (var o in orders.GetOrders(World))
 			{
 				UnitOrders.ProcessOrder(this, World, clientId, o);
@@ -168,10 +156,6 @@ namespace OpenRA.Network
 
 		public void ReceiveOrders(int clientId, (int Frame, OrderPacket Orders) orders)
 		{
-			// HACK: The shellmap relies on ticking a disposed OM
-			if (disposed && World.Type != WorldType.Shellmap)
-				return;
-
 			if (pendingOrders.TryGetValue(clientId, out var queue))
 				queue.Enqueue((orders.Frame, orders.Orders));
 			else

OpenRA.Game/World.cs

@@ -574,6 +574,12 @@ namespace OpenRA
 			while (frameEndActions.Count != 0)
 				frameEndActions.Dequeue()(this);
 
+			// HACK: The shellmap OrderManager is owned by its world in order to avoid
+			// problems with having multiple OMs active when joining a game lobby from the main menu.
+			// A matching check in Game.JoinInner handles OM disposal for all other cases.
+			if (Type == WorldType.Shellmap)
+				OrderManager.Dispose();
+
 			Game.FinishBenchmark();
 		}
 	}