Ensure the PR session manager is initialized.

Author: grokys

src/GitHub.Exports.Reactive/Services/IPullRequestSessionManager.cs

@@ -31,6 +31,18 @@ public interface IPullRequestSessionManager : INotifyPropertyChanged
         /// </returns>
         IPullRequestSession CurrentSession { get; }
 
+        /// <summary>
+        /// Ensures that the service is initialized.
+        /// </summary>
+        /// <returns>A task that when completed indicates that the service is initialized.</returns>
+        /// <remarks>
+        /// If you are simplying monitoring changes to the <see cref="CurrentSession"/> then you
+        /// don't need to call this method: <see cref="CurrentSession"/> will be updated on
+        /// initialization. If however, you want to be sure that <see cref="CurrentSession"/> is
+        /// initialized, you can await the task returned from this method.
+        /// </remarks>
+        Task EnsureInitialized();
+
         /// <summary>
         /// Gets an <see cref="IPullRequestSessionFile"/> that tracks the live state of a document.
         /// </summary>

src/GitHub.InlineReviews/Services/PullRequestSessionManager.cs

@@ -36,6 +36,7 @@ public class PullRequestSessionManager : ReactiveObject, IPullRequestSessionMana
         readonly IModelServiceFactory modelServiceFactory;
         readonly Dictionary<Tuple<string, int>, WeakReference<PullRequestSession>> sessions =
             new Dictionary<Tuple<string, int>, WeakReference<PullRequestSession>>();
+        TaskCompletionSource<object> initialized;
         IPullRequestSession currentSession;
         ILocalRepositoryModel repository;
 
@@ -65,6 +66,7 @@ public PullRequestSessionManager(
             this.sessionService = sessionService;
             this.connectionManager = connectionManager;
             this.modelServiceFactory = modelServiceFactory;
+            initialized = new TaskCompletionSource<object>(null);
 
             Observable.FromEventPattern(teamExplorerContext, nameof(teamExplorerContext.StatusChanged))
                 .ObserveOn(RxApp.MainThreadScheduler)
@@ -82,6 +84,10 @@ public IPullRequestSession CurrentSession
             private set { this.RaiseAndSetIfChanged(ref currentSession, value); }
         }
 
+        /// <inheritdoc/>
+        public Task EnsureInitialized() => initialized.Task;
+
+        /// <inheritdoc/>
         public async Task<IPullRequestSessionFile> GetLiveFile(
             string relativePath,
             ITextView textView,
@@ -230,6 +236,7 @@ async Task StatusChanged()
                 }
 
                 CurrentSession = session;
+                initialized.SetResult(null);
             }
             catch (Exception e)
             {

src/GitHub.VisualStudio/Menus/ShowCurrentPullRequest.cs

@@ -26,6 +26,8 @@ public async void Activate(object data = null)
             try
             {
                 var pullRequestSessionManager = ServiceProvider.ExportProvider.GetExportedValueOrDefault<IPullRequestSessionManager>();
+                await pullRequestSessionManager.EnsureInitialized();
+
                 var session = pullRequestSessionManager?.CurrentSession;
                 if (session == null)
                 {