Fix ArgumentOutOfRangeException thrown when changing color of the error prompt (#967)

Author: daxian-dbw

PSReadLine/Render.cs

@@ -377,14 +377,45 @@ void UpdateColorsIfNecessary(string newColor)
                     // We need to update the prompt
 
                     // promptBufferCells is the number of visible characters in the prompt
-                    var promptBufferCells = LengthInBufferCells(promptText);
-                    _console.CursorLeft -= promptBufferCells;
-                    var color = renderData.errorPrompt ? _options._errorColor : defaultColor;
-                    if (renderData.errorPrompt && promptBufferCells != promptText.Length)
-                        promptText = promptText.Substring(promptText.Length - promptBufferCells);
-                    UpdateColorsIfNecessary(color);
-                    _console.Write(promptText);
-                    _console.Write("\x1b[0m");
+                    int promptBufferCells = LengthInBufferCells(promptText);
+                    bool renderErrorPrompt = false;
+
+                    if (_console.CursorLeft >= promptBufferCells)
+                    {
+                        renderErrorPrompt = true;
+                        _console.CursorLeft -= promptBufferCells;
+                    }
+                    else
+                    {
+                        // The 'CursorLeft' could be less than error-prompt-cell-length in one of the following 3 cases:
+                        //   1. console buffer was resized, which causes the initial cursor to appear on the next line;
+                        //   2. prompt string gets longer (e.g. by 'cd' into nested folders), which causes the line to be wrapped to the next line;
+                        //   3. the prompt function was changed, which causes the new prompt string is shorter than the error prompt.
+                        // Here, we always assume it's the case 1 or 2, and wrap back to the previous line to change the error prompt color.
+                        // In case of case 3, the rendering would be off, but it's more of a user error because the prompt is changed without
+                        // updating 'PromptText' with 'Set-PSReadLineOption'.
+
+                        int diffs = promptBufferCells - _console.CursorLeft;
+                        int newX = bufferWidth - diffs % bufferWidth;
+                        int newY = _initialY - diffs / bufferWidth - 1;
+
+                        // newY could be less than 0 if 'PromptText' is manually set to be a long string.
+                        if (newY >= 0)
+                        {
+                            renderErrorPrompt = true;
+                            _console.SetCursorPosition(newX, newY);
+                        }
+                    }
+
+                    if (renderErrorPrompt)
+                    {
+                        var color = renderData.errorPrompt ? _options._errorColor : defaultColor;
+                        if (renderData.errorPrompt && promptBufferCells != promptText.Length)
+                            promptText = promptText.Substring(promptText.Length - promptBufferCells);
+                        UpdateColorsIfNecessary(color);
+                        _console.Write(promptText);
+                        _console.Write("\x1b[0m");
+                    }
                 }
             }