From 078a2b3cc4bcea5a07f0d08e1e11097a0ba48335 Mon Sep 17 00:00:00 2001
From: Dongbo Wang <dongbow@microsoft.com>
Date: Mon, 20 Sep 2021 09:26:12 -0700
Subject: [PATCH] Fix rendering when continuation prompt is an empty string
 (#2875)

---
 PSReadLine/Render.cs | 14 +++++++++--
 test/RenderTest.cs   | 59 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 71 insertions(+), 2 deletions(-)

diff --git a/PSReadLine/Render.cs b/PSReadLine/Render.cs
index 72ccbc27..f9787700 100644
--- a/PSReadLine/Render.cs
+++ b/PSReadLine/Render.cs
@@ -205,8 +205,11 @@ void RenderOneChar(char charToRender, bool toEmphasize)
                     // the previous rendering string.
                     activeColor = string.Empty;
 
-                    UpdateColorsIfNecessary(Options._continuationPromptColor);
-                    _consoleBufferLines[currentLogicalLine].Append(Options.ContinuationPrompt);
+                    if (Options.ContinuationPrompt.Length > 0)
+                    {
+                        UpdateColorsIfNecessary(Options._continuationPromptColor);
+                        _consoleBufferLines[currentLogicalLine].Append(Options.ContinuationPrompt);
+                    }
 
                     if (inSelectedRegion)
                     {
@@ -465,6 +468,13 @@ private bool RenderErrorPrompt(RenderData renderData, string defaultColor)
         /// </summary>
         private int PhysicalLineCount(int columns, bool isFirstLogicalLine, out int lenLastPhysicalLine)
         {
+            if (columns == 0)
+            {
+                // This could happen for a new logical line with an empty-string continuation prompt.
+                lenLastPhysicalLine = 0;
+                return 1;
+            }
+
             int cnt = 1;
             int bufferWidth = _console.BufferWidth;
 
diff --git a/test/RenderTest.cs b/test/RenderTest.cs
index 1ef7b263..bfbffd28 100644
--- a/test/RenderTest.cs
+++ b/test/RenderTest.cs
@@ -203,6 +203,65 @@ public void MultiLine()
                 _.Enter, CheckThat(() => AssertCursorLeftTopIs(0, 2))));
         }
 
+        [SkippableFact]
+        public void MultiLine_ScreenCheck()
+        {
+            TestSetup(KeyMode.Cmd);
+
+            var defaultContinuationPrompt = PSConsoleReadLineOptions.DefaultContinuationPrompt;
+            var defaultContinuationPromptColors = Tuple.Create(_console.ForegroundColor, _console.BackgroundColor);
+
+            Test("@'\n\n hello\n\n world\n'@",
+                 Keys(
+                    "@'",     _.Enter, _.Enter,
+                    " hello", _.Enter, _.Enter,
+                    " world", _.Enter, "'@",
+                        CheckThat(() => AssertScreenIs(6,
+                            TokenClassification.String, "@'",
+                            NextLine,
+                            defaultContinuationPromptColors, defaultContinuationPrompt,
+                            NextLine,
+                            defaultContinuationPromptColors, defaultContinuationPrompt,
+                            TokenClassification.String, " hello",
+                            NextLine,
+                            defaultContinuationPromptColors, defaultContinuationPrompt,
+                            NextLine,
+                            defaultContinuationPromptColors, defaultContinuationPrompt,
+                            TokenClassification.String, " world",
+                            NextLine,
+                            defaultContinuationPromptColors, defaultContinuationPrompt,
+                            TokenClassification.String, "'@"))
+                 ));
+
+            string emptyLine = new string(' ', _console.BufferWidth);
+            // Set the continuation prompt to be an empty string.
+            var setOption = new SetPSReadLineOption { ContinuationPrompt = string.Empty };
+            PSConsoleReadLine.SetOptions(setOption);
+
+            try
+            {
+                Test("@'\n\n hello\n\n world\n'@",
+                     Keys(
+                        "@'", _.Enter, _.Enter,
+                        " hello", _.Enter, _.Enter,
+                        " world", _.Enter, "'@",
+                            CheckThat(() => AssertScreenIs(6,
+                                TokenClassification.String, "@'", NextLine,
+                                TokenClassification.None, emptyLine,
+                                TokenClassification.String, " hello", NextLine,
+                                TokenClassification.None, emptyLine,
+                                TokenClassification.String, " world", NextLine,
+                                TokenClassification.String, "'@"))
+                 ));
+            }
+            finally
+            {
+                // Restore to the default continuation prompt.
+                setOption.ContinuationPrompt = defaultContinuationPrompt;
+                PSConsoleReadLine.SetOptions(setOption);
+            }
+        }
+
         [SkippableFact]
         public void LongLine()
         {