Fix cluttered debug history

This change fixes an issue where background commands would be added
to PowerShell's history.  This was due to a limitation in the
PowerShell debugger where the only way commands are excluded is if
the command is part of a hard coded set of commands. As a workaround,
a command from that set (prompt) is added as the first statement.

Resolves PowerShell/vscode-powershell#873

Author: SeeminglyScience

src/PowerShellEditorServices/Session/PowerShell3Operations.cs

@@ -33,8 +33,10 @@ public IEnumerable<TResult> ExecuteCommandInDebugger<TResult>(
         {
             IEnumerable<TResult> executionResult = null;
 
-            using (var nestedPipeline = currentRunspace.CreateNestedPipeline())
+            string historyString = psCommand.Commands[0].CommandText;
+            using (var nestedPipeline = currentRunspace.CreateNestedPipeline(historyString, sendOutputToHost))
             {
+                nestedPipeline.Commands.Clear();
                 foreach (var command in psCommand.Commands)
                 {
                     nestedPipeline.Commands.Add(command);

src/PowerShellEditorServices/Session/PowerShell4Operations.cs

@@ -13,6 +13,15 @@ namespace Microsoft.PowerShell.EditorServices.Session
 {
     internal class PowerShell4Operations : IVersionSpecificOperations
     {
+        private static SortedSet<string> s_noHistoryCommandNames = new SortedSet<string>(StringComparer.OrdinalIgnoreCase)
+        {
+            "prompt",
+            "Set-PSDebuggerAction",
+            "Get-PSDebuggerStopArgs",
+            "Set-PSDebugMode",
+            "TabExpansion2"
+        };
+
         public void ConfigureDebugger(Runspace runspace)
         {
 #if !PowerShellv3
@@ -54,6 +63,24 @@ public IEnumerable<TResult> ExecuteCommandInDebugger<TResult>(
                     };
             }
 
+            // There's no way to tell the debugger not to add the command to history. It does however,
+            // check if the first command is in a static list of commands that shouldn't be added
+            // to history. We use that here to get around that limitation.
+            if (!sendOutputToHost && !s_noHistoryCommandNames.Contains(psCommand.Commands[0].CommandText))
+            {
+                var newCommand = new PSCommand()
+                    .AddCommand("prompt")
+                    .AddCommand("Microsoft.PowerShell.Core\\Out-Null")
+                    .AddStatement();
+
+                foreach (Command command in psCommand.Commands)
+                {
+                    newCommand.AddCommand(command);
+                }
+
+                psCommand = newCommand;
+            }
+
             DebuggerCommandResults commandResults =
                 currentRunspace.Debugger.ProcessCommand(
                     psCommand,

src/PowerShellEditorServices/Session/PowerShellContext.cs

@@ -1490,10 +1490,12 @@ private SessionDetails GetSessionDetailsInRunspace(Runspace runspace)
                         {
                             powerShell.Runspace = runspace;
                             powerShell.Commands = command;
+                            var invocationSettings = new PSInvocationSettings();
+                            invocationSettings.AddToHistory = false;
 
                             return
                                 powerShell
-                                    .Invoke()
+                                    .Invoke(null, invocationSettings)
                                     .FirstOrDefault();
                         }
                     });