Fix race condition

The `ListenToCompletionState` subscription was triggering a navigation
request on the `Next` callback. Depending on how fast VS responds, this
can cause the Sync section to be disposed, along with the `UIController`
instance, before the handler returns, which would cause `UIController`
to crash.

Make sure we only navigate away once the `ListenToCompletionState`
observable is completed, and also tweak the way `Dispose` happens in
`UIController` to minimize races.

Author: shana

src/GitHub.App/Controllers/UIController.cs

@@ -152,6 +152,7 @@ void End(bool success)
         {
             uiProvider.RemoveService(typeof(IConnection));
             transition.OnCompleted();
+            completion?.OnNext(success);
             completion?.OnCompleted();
             completion = null;
         }
@@ -291,15 +292,19 @@ protected virtual void Dispose(bool disposing)
             if (disposing)
             {
                 if (disposed) return;
+                disposed = true;
 
-                Debug.WriteLine("Disposing ({0})", GetHashCode());
-                disposables.Dispose();
-                transition?.Dispose();
-                completion?.Dispose();
                 if (connectionAdded != null)
                     connectionManager.Connections.CollectionChanged -= connectionAdded;
                 connectionAdded = null;
-                disposed = true;
+
+                var tr = transition;
+                var cmp = completion;
+                transition = null;
+                completion = null;
+                disposables.Dispose();
+                tr?.Dispose();
+                cmp?.Dispose();
             }
         }
 

src/GitHub.VisualStudio/TeamExplorer/Sync/GitHubPublishSection.cs

@@ -117,10 +117,13 @@ void ShowPublish()
             disposable = uiflow;
             var ui = uiflow.Value;
             var creation = ui.SelectFlow(UIControllerFlow.Publish);
-            ui.ListenToCompletionState().Subscribe(_ => { }, () =>
+            bool success = false;
+            ui.ListenToCompletionState().Subscribe(s => success = s, () =>
             {
+                // there's no real cancel button in the publish form, but if support a back button there, then we want to hide the form
                 IsVisible = false;
-                ServiceProvider.TryGetService<ITeamExplorer>()?.NavigateToPage(new Guid(TeamExplorerPageIds.Home), null);
+                if (success)
+                    ServiceProvider.TryGetService<ITeamExplorer>()?.NavigateToPage(new Guid(TeamExplorerPageIds.Home), null);
             });
 
             creation.Subscribe(c =>