IN PROGRESS: Fix prompt input re-rendering on *nix systems

Author: daviwil

src/PowerShellEditorServices/Console/ConsoleReadLine.cs

@@ -19,8 +19,9 @@ namespace Microsoft.PowerShell.EditorServices.Console
 
     internal class ConsoleReadLine
     {
-        #region Private Fields
+        #region Private Field
 
+        private bool isUnix = false;
         private PowerShellContext powerShellContext;
         private AsyncQueue<ConsoleKeyInfo> readKeyQueue = new AsyncQueue<ConsoleKeyInfo>();
 
@@ -31,6 +32,8 @@ internal class ConsoleReadLine
         public ConsoleReadLine(PowerShellContext powerShellContext)
         {
             this.powerShellContext = powerShellContext;
+            // TODO: Change me?
+            this.isUnix = false;
         }
 
         #endregion
@@ -186,11 +189,12 @@ private async Task<string> ReadLine(bool isCommandLine, CancellationToken cancel
                         inputBeforeCompletion = inputLine.ToString();
                         inputAfterCompletion = null;
 
-                        int cursorColumn =
-                            this.CalculateIndexFromCursor(
-                                promptStartCol,
-                                promptStartRow,
-                                consoleWidth);
+                        // int cursorColumn =
+                        //     this.CalculateIndexFromCursor(
+                        //         promptStartCol,
+                        //         promptStartRow,
+                        //         consoleWidth);
+                        int cursorColumn = currentCursorIndex;
 
                         // TODO: This logic should be moved to AstOperations or similar!
 
@@ -271,13 +275,27 @@ private async Task<string> ReadLine(bool isCommandLine, CancellationToken cancel
                 else if (keyInfo.Key == ConsoleKey.Home)
                 {
                     currentCompletion = null;
+                    int oldCursorIndex = currentCursorIndex;
                     currentCursorIndex = 0;
 
-                    this.MoveCursorToIndex(
-                        promptStartCol,
-                        promptStartRow,
-                        consoleWidth,
-                        currentCursorIndex);
+                    if (this.isUnix)
+                    {
+                        this.RenderInputLine(
+                            inputLine,
+                            promptStartCol,
+                            promptStartRow,
+                            consoleWidth,
+                            oldCursorIndex,
+                            currentCursorIndex);
+                    }
+                    else
+                    {
+                        this.MoveCursorToIndex(
+                            promptStartCol,
+                            promptStartRow,
+                            consoleWidth,
+                            currentCursorIndex);
+                    }
                 }
                 else if (keyInfo.Key == ConsoleKey.RightArrow)
                 {
@@ -607,6 +625,47 @@ private int InsertInput(
             return finalCursorIndex != -1 ? finalCursorIndex : inputLine.Length;
         }
 
+        private void RenderInputLine(
+            StringBuilder inputLine,
+            int promptStartCol,
+            int promptStartRow,
+            int consoleWidth,
+            int cursorIndex,
+            int finalCursorIndex,
+            int overrunCount = 5)
+        {
+          this.CalculateCursorFromIndex(
+                promptStartCol,
+                promptStartRow,
+                consoleWidth,
+                cursorIndex,
+                out int newCol,
+                out int newRow);
+
+            Console.SetCursorPosition(newCol, newRow);
+
+            // Re-render affected section
+            Console.Write(
+                inputLine.ToString(
+                    cursorIndex,
+                    inputLine.Length - cursorIndex));
+
+            Console.Write(
+                new string(
+                    ' ',
+                    overrunCount));
+
+            this.CalculateCursorFromIndex(
+                promptStartCol,
+                promptStartRow,
+                consoleWidth,
+                finalCursorIndex,
+                out newCol,
+                out newRow);
+
+            Console.SetCursorPosition(newCol, newRow);
+        }
+
         private void MoveCursorToIndex(
             int promptStartCol,
             int promptStartRow,