Fix #159: LanguageServer.Shutdown hangs on flush

src/PowerShellEditorServices.Protocol/Server/LanguageServer.cs

@@ -80,10 +80,10 @@ protected override void Initialize()
             this.SetRequestHandler(DebugAdapterMessages.EvaluateRequest.Type, this.HandleEvaluateRequest);
         }
 
-        protected override void Shutdown()
+        protected override async Task Shutdown()
         {
             // Make sure remaining output is flushed before exiting
-            this.outputDebouncer.Flush().Wait();
+            await this.outputDebouncer.Flush();
 
             Logger.Write(LogLevel.Normal, "Language service is shutting down...");
 

src/PowerShellEditorServices.Protocol/Server/LanguageServerBase.cs

@@ -34,11 +34,9 @@ protected override Task OnStart()
             return Task.FromResult(true);
         }
 
-        protected override Task OnStop()
+        protected override async Task OnStop()
         {
-            this.Shutdown();
-
-            return Task.FromResult(true);
+            await this.Shutdown();
         }
 
         /// <summary>
@@ -49,37 +47,37 @@ protected override Task OnStop()
 
         /// <summary>
         /// Can be overridden by the subclass to provide shutdown
-        /// logic before the server exits.
+        /// logic before the server exits.  Subclasses do not need
+        /// to invoke or return the value of the base implementation.
         /// </summary>
-        protected virtual void Shutdown()
+        protected virtual Task Shutdown()
         {
             // No default implementation yet.
+            return Task.FromResult(true);
         }
 
-        private Task HandleShutdownRequest(
+        private async Task HandleShutdownRequest(
             object shutdownParams,
             RequestContext<object> requestContext)
         {
             // Allow the implementor to shut down gracefully
-            this.Shutdown();
+            await this.Shutdown();
 
-            return requestContext.SendResult(new object());
+            await requestContext.SendResult(new object());
         }
 
-        private Task HandleExitNotification(
+        private async Task HandleExitNotification(
             object exitParams,
             EventContext eventContext)
         {
             // Stop the server channel
-            this.Stop();
+            await this.Stop();
 
             // Notify any waiter that the server has exited
             if (this.serverExitedTask != null)
             {
                 this.serverExitedTask.SetResult(true);
             }
-
-            return Task.FromResult(true);
         }
     }
 }