Fix double prompt display when integrated console starts up

This change fixes an issue where the user's custom prompt function is
displayed twice when the integrated console host starts up.  This issue
was a timing issue caused by the ConsoleService not being appropriately
aware of when the input loop had been started.

Resolves PowerShell/vscode-powershell#770.

Author: daviwil

src/PowerShellEditorServices/Console/ConsoleService.cs

@@ -24,6 +24,7 @@ public class ConsoleService : IConsoleHost
     {
         #region Fields
 
+        private bool isReadLoopStarted;
         private ConsoleReadLine consoleReadLine;
         private PowerShellContext powerShellContext;
 
@@ -106,21 +107,8 @@ public void StartReadLoop()
         {
             if (this.EnableConsoleRepl)
             {
-                if (this.readLineCancellationToken == null)
-                {
-                    this.readLineCancellationToken = new CancellationTokenSource();
-
-                    var terminalThreadTask =
-                        Task.Factory.StartNew(
-                            async () =>
-                            {
-                                await this.StartReplLoop(this.readLineCancellationToken.Token);
-                            });
-                }
-                else
-                {
-                    Logger.Write(LogLevel.Verbose, "StartReadLoop called while read loop is already running");
-                }
+                this.isReadLoopStarted = true;
+                this.InnerStartReadLoop();
             }
         }
 
@@ -129,15 +117,8 @@ public void StartReadLoop()
         /// </summary>
         public void CancelReadLoop()
         {
-            if (this.readLineCancellationToken != null)
-            {
-                // Set this to false so that Ctrl+C isn't trapped by any
-                // lingering ReadKey
-                Console.TreatControlCAsInput = false;
-
-                this.readLineCancellationToken.Cancel();
-                this.readLineCancellationToken = null;
-            }
+            this.isReadLoopStarted = false;
+            this.InnerCancelReadLoop();
         }
 
         /// <summary>
@@ -148,7 +129,7 @@ public void CancelReadLoop()
         /// <returns>A Task that can be awaited for completion.</returns>
         public async Task ExecuteScriptAtPath(string scriptPath, string arguments = null)
         {
-            this.CancelReadLoop();
+            this.InnerCancelReadLoop();
 
             // If we don't escape wildcard characters in the script path, the script can
             // fail to execute if say the script name was foo][.ps1.
@@ -161,7 +142,7 @@ await this.powerShellContext.ExecuteScriptString(
                 true,
                 false);
 
-            this.StartReadLoop();
+            this.InnerStartReadLoop();
         }
 
         /// <summary>
@@ -273,6 +254,41 @@ private void WriteDebuggerBanner(DebuggerStopEventArgs eventArgs)
             }
         }
 
+        private void InnerStartReadLoop()
+        {
+            if (this.EnableConsoleRepl)
+            {
+                if (this.readLineCancellationToken == null)
+                {
+                    this.readLineCancellationToken = new CancellationTokenSource();
+
+                    var terminalThreadTask =
+                        Task.Factory.StartNew(
+                            async () =>
+                            {
+                                await this.StartReplLoop(this.readLineCancellationToken.Token);
+                            });
+                }
+                else
+                {
+                    Logger.Write(LogLevel.Verbose, "InnerStartReadLoop called while read loop is already running");
+                }
+            }
+        }
+
+        private void InnerCancelReadLoop()
+        {
+            if (this.readLineCancellationToken != null)
+            {
+                // Set this to false so that Ctrl+C isn't trapped by any
+                // lingering ReadKey
+                Console.TreatControlCAsInput = false;
+
+                this.readLineCancellationToken.Cancel();
+                this.readLineCancellationToken = null;
+            }
+        }
+
         private async Task StartReplLoop(CancellationToken cancellationToken)
         {
             do
@@ -431,20 +447,20 @@ private void activePromptHandler_PromptCancelled(object sender, EventArgs e)
         private void PowerShellContext_DebuggerStop(object sender, System.Management.Automation.DebuggerStopEventArgs e)
         {
             // Cancel any existing prompt first
-            this.CancelReadLoop();
+            this.InnerCancelReadLoop();
 
             this.WriteDebuggerBanner(e);
-            this.StartReadLoop();
+            this.InnerStartReadLoop();
         }
 
         private void PowerShellContext_DebuggerResumed(object sender, System.Management.Automation.DebuggerResumeAction e)
         {
-            this.CancelReadLoop();
+            this.InnerCancelReadLoop();
         }
 
         private void PowerShellContext_ExecutionStatusChanged(object sender, ExecutionStatusChangedEventArgs eventArgs)
         {
-            if (this.EnableConsoleRepl)
+            if (this.EnableConsoleRepl && this.isReadLoopStarted)
             {
                 if (eventArgs.ExecutionStatus == ExecutionStatus.Aborted)
                 {
@@ -464,12 +480,12 @@ private void PowerShellContext_ExecutionStatusChanged(object sender, ExecutionSt
                     if (eventArgs.ExecutionStatus != ExecutionStatus.Running)
                     {
                         // Execution has completed, start the input prompt
-                        this.StartReadLoop();
+                        this.InnerStartReadLoop();
                     }
                     else
                     {
                         // A new command was started, cancel the input prompt
-                        this.CancelReadLoop();
+                        this.InnerCancelReadLoop();
                         this.WriteOutput(string.Empty);
                     }
                 }
@@ -478,9 +494,9 @@ private void PowerShellContext_ExecutionStatusChanged(object sender, ExecutionSt
                     (eventArgs.ExecutionStatus == ExecutionStatus.Failed ||
                      eventArgs.HadErrors))
                 {
-                    this.CancelReadLoop();
+                    this.InnerCancelReadLoop();
                     this.WriteOutput(string.Empty);
-                    this.StartReadLoop();
+                    this.InnerStartReadLoop();
                 }
             }
         }