Ensure GitHubPane initializes view model is initialized.

When the GitHub pane is shown from VS rather than our own code, kick off an initialization of the view model. This means we can't be sure of the state of the view model's initialization so make subsequent calls to the view model async either wait for an ongoing initialization, or exit if already initialized.

Author: grokys

src/GitHub.App/ViewModels/GitHubPane/GitHubPaneViewModel.cs

@@ -46,6 +46,8 @@ public sealed class GitHubPaneViewModel : ViewModelBase, IGitHubPaneViewModel, I
         readonly ReactiveCommand<Unit> refresh;
         readonly ReactiveCommand<Unit> showPullRequests;
         readonly ReactiveCommand<object> openInBrowser;
+        readonly SemaphoreSlim initializing = new SemaphoreSlim(1);
+        bool initialized;
         IViewModel content;
         ILocalRepositoryModel localRepository;
         string searchQuery;
@@ -198,26 +200,37 @@ public void Dispose()
         /// <inheritdoc/>
         public async Task InitializeAsync(IServiceProvider paneServiceProvider)
         {
-            await UpdateContent(teamExplorerContext.ActiveRepository);
-            teamExplorerContext.WhenAnyValue(x => x.ActiveRepository)
-               .Skip(1)
-               .ObserveOn(RxApp.MainThreadScheduler)
-               .Subscribe(x => UpdateContent(x).Forget());
-
-            connectionManager.Connections.CollectionChanged += (_, __) => UpdateContent(LocalRepository).Forget();
-
-            BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.pullRequestCommand, showPullRequests);
-            BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.backCommand, navigator.NavigateBack);
-            BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.forwardCommand, navigator.NavigateForward);
-            BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.refreshCommand, refresh);
-            BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.githubCommand, openInBrowser);
-
-            paneServiceProvider.AddCommandHandler(Guids.guidGitHubToolbarCmdSet, PkgCmdIDList.helpCommand,
-                 (_, __) =>
-                 {
-                     browser.OpenUrl(new Uri(GitHubUrls.Documentation));
-                     usageTracker.IncrementCounter(x => x.NumberOfGitHubPaneHelpClicks).Forget();
-                 });
+            await initializing.WaitAsync();
+            if (initialized) return;
+
+            try
+            {
+                await UpdateContent(teamExplorerContext.ActiveRepository);
+                teamExplorerContext.WhenAnyValue(x => x.ActiveRepository)
+                   .Skip(1)
+                   .ObserveOn(RxApp.MainThreadScheduler)
+                   .Subscribe(x => UpdateContent(x).Forget());
+
+                connectionManager.Connections.CollectionChanged += (_, __) => UpdateContent(LocalRepository).Forget();
+
+                BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.pullRequestCommand, showPullRequests);
+                BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.backCommand, navigator.NavigateBack);
+                BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.forwardCommand, navigator.NavigateForward);
+                BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.refreshCommand, refresh);
+                BindNavigatorCommand(paneServiceProvider, PkgCmdIDList.githubCommand, openInBrowser);
+
+                paneServiceProvider.AddCommandHandler(Guids.guidGitHubToolbarCmdSet, PkgCmdIDList.helpCommand,
+                     (_, __) =>
+                     {
+                         browser.OpenUrl(new Uri(GitHubUrls.Documentation));
+                         usageTracker.IncrementCounter(x => x.NumberOfGitHubPaneHelpClicks).Forget();
+                     });
+            }
+            finally
+            {
+                initialized = true;
+                initializing.Release();
+            }
         }
 
         /// <inheritdoc/>

src/GitHub.VisualStudio/UI/GitHubPane.cs

@@ -89,6 +89,7 @@ public void Initialize(IServiceProvider serviceProvider)
 
                 var factory = provider.GetService<IViewViewModelFactory>();
                 viewModel = provider.ExportProvider.GetExportedValue<IGitHubPaneViewModel>();
+                viewModel.InitializeAsync(this).Forget();
 
                 View = factory.CreateView<IGitHubPaneViewModel>();
                 View.DataContext = viewModel;