Add function InvokePrompt to re-evaluate prompt

InvokePrompt can be used from a custom key handler to invoke the
prompt function again.  This is done in a way that minimizes changes
to the display - the previous prompt is overwritten and the cursor
is placed where it was before the prompt was evaluated previously.

The current input is also preserved.

Author: lzybkr

PSReadLine/Cmdlets.cs

@@ -453,14 +453,14 @@ public class SetKeyHandlerCommand : PSCmdlet
                      "CharacterSearchBackward", "ClearScreen", "Complete", "Copy", "Cut",
                      "DeleteChar", "DigitArgument", "DisableDemoMode", "EnableDemoMode", "EndOfHistory",
                      "EndOfLine", "ExchangePointAndMark", "ForwardChar", "ForwardDeleteLine", "ForwardSearchHistory",
-                     "ForwardWord", "GotoBrace", "HistorySearchBackward", "HistorySearchForward", "KillLine",
-                     "KillRegion", "KillWord", "NextHistory", "NextWord", "Paste",
-                     "PossibleCompletions", "PreviousHistory", "Redo", "ReverseSearchHistory", "RevertLine",
-                     "SelectBackwardChar", "SelectBackwardWord", "SelectForwardChar", "SelectForwardWord", "SelectNextWord",
-                     "SelectShellBackwardWord", "SelectShellForwardWord", "SelfInsert", "SetMark", "ShellBackwardKillWord",
-                     "ShellBackwardWord", "ShellForwardWord", "ShellKillWord", "ShowKeyBindings", "TabCompleteNext",
-                     "TabCompletePrevious", "Undo", "UnixWordRubout", "WhatIsKey", "Yank",
-                     "YankLastArg", "YankNthArg", "YankPop")]
+                     "ForwardWord", "GotoBrace", "HistorySearchBackward", "HistorySearchForward", "InvokePrompt",
+                     "KillLine", "KillRegion", "KillWord", "NextHistory", "NextWord",
+                     "Paste", "PossibleCompletions", "PreviousHistory", "Redo", "ReverseSearchHistory",
+                     "RevertLine", "SelectBackwardChar", "SelectBackwardWord", "SelectForwardChar", "SelectForwardWord",
+                     "SelectNextWord", "SelectShellBackwardWord", "SelectShellForwardWord", "SelfInsert", "SetMark",
+                     "ShellBackwardKillWord", "ShellBackwardWord", "ShellForwardWord", "ShellKillWord", "ShowKeyBindings",
+                     "TabCompleteNext", "TabCompletePrevious", "Undo", "UnixWordRubout", "WhatIsKey",
+                     "Yank", "YankLastArg", "YankNthArg", "YankPop")]
         [Parameter(Position = 1, Mandatory = true, ParameterSetName = "Function")]
         public string Function { get; set; }
 

PSReadLine/PSReadLineResources.Designer.cs

@@ -354,4 +354,7 @@
   <data name="PowerShellColorTable" xml:space="preserve">
     <value>\red0\green0\blue0\red0\green0\blue128\red0\green128\blue0\red0\green128\blue128\red128\green0\blue0\red1\green36\blue86\red238\green237\blue240\red192\green192\blue192\red128\green128\blue128\red0\green0\blue255\red0\green255\blue0\red0\green255\blue255\red255\green0\blue0\red255\green0\blue255\red255\gree\red0\green0\blue0;\red0\green0\blue128;\red0\green128\blue0;\red0\green128\blue128;\red128\green0\blue0;\red1\green36\blue86;\red238\green237\blue240;\red192\green192\blue192;\red128\green128\blue128;\red0\green0\blue255;\red0\green255\blue0;\red0\green255\blue255;\red255\green0\blue0;\red255\green0\blue255;\red255\green255\blue0;\red255\green255\blue255;</value>
   </data>
+  <data name="InvokePromptDescription" xml:space="preserve">
+    <value>Erases the current prompt and calls the prompt function to redisplay the prompt</value>
+  </data>
 </root>

PSReadLine/PSReadLineResources.resx

@@ -3779,6 +3779,39 @@ private static void DumpScreenToClipboard(int top, int count)
             Clipboard.SetDataObject(dataObject, copy: true);
         }
 
+        /// <summary>
+        /// Erases the current prompt and calls the prompt function to redisplay
+        /// the prompt.  Useful for custom key handlers that change state, e.g.
+        /// change the current directory.
+        /// </summary>
+        public static void InvokePrompt(ConsoleKeyInfo? key = null, object arg = null)
+        {
+            var currentBuffer = _singleton._buffer.ToString();
+            var currentPos = _singleton._current;
+            _singleton._buffer.Clear();
+            _singleton._current = 0;
+            for (int i = 0; i < _singleton._consoleBuffer.Length; i++)
+            {
+                _singleton._consoleBuffer[i].UnicodeChar = ' ';
+                _singleton._consoleBuffer[i].ForegroundColor = Console.ForegroundColor;
+                _singleton._consoleBuffer[i].BackgroundColor = Console.BackgroundColor;
+            }
+            _singleton.Render();
+            Console.CursorLeft = 0;
+            Console.CursorTop = _singleton._initialY;
+
+            var ps = PowerShell.Create(RunspaceMode.CurrentRunspace);
+            ps.AddCommand("prompt");
+            var result = ps.Invoke<string>();
+            var strResult = result.Count == 1 ? result[0] : "PS> ";
+            Console.Write(strResult);
+
+            _singleton._consoleBuffer = ReadBufferLines(_singleton._initialY, 1 + _singleton.Options.ExtraPromptLineCount);
+            _singleton._buffer.Append(currentBuffer);
+            _singleton._current = currentPos;
+            _singleton.Render();
+        }
+
         #endregion Miscellaneous bindable functions
 
         private void SetOptionsInternal(SetPSReadlineOption options)

PSReadLine/ReadLine.cs

@@ -384,6 +384,12 @@ LONG DESCRIPTION
         Turn on demo mode.  Displays a window below the input line that shows which
         keys are typed.
 
+    InvokePrompt             (Cmd: unbound              Emacs: unbound)
+
+        Erases the current prompt and calls the prompt function to redisplay
+        the prompt.  Useful for custom key handlers that change state, e.g.
+        change the current directory.
+
     WhatIsKey                (Cmd: <Alt+?>              Emacs: <Alt+?>)
 
         Read a key or chord and display the key binding.