Prevent crash in GotoFirstNonBlankOfLine (#2050) (#2051)

Author: springcomp

PSReadLine/Position.cs

@@ -11,28 +11,17 @@ public partial class PSConsoleReadLine
         /// <param name="current">The position in the current logical line.</param>
         private static int GetBeginningOfLinePos(int current)
         {
-            var newCurrent = current;
-
-            if (_singleton.LineIsMultiLine())
+            int i = Math.Max(0, current);
+            while (i > 0)
             {
-                int i = Math.Max(0, current);
-                while (i > 0)
+                if (_singleton._buffer[--i] == '\n')
                 {
-                    if (_singleton._buffer[--i] == '\n')
-                    {
-                        i += 1;
-                        break;
-                    }
+                    i += 1;
+                    break;
                 }
-
-                newCurrent = i;
-            }
-            else
-            {
-                newCurrent = 0;
             }
 
-            return newCurrent;
+            return i;
         }
 
         /// <summary>
@@ -114,7 +103,7 @@ private static int GetFirstNonBlankOfLogicalLinePos(int current)
 
             var newCurrent = beginningOfLine;
 
-            while (IsVisibleBlank(newCurrent))
+            while (newCurrent < _singleton._buffer.Length && IsVisibleBlank(newCurrent))
             {
                 newCurrent++;
             }

test/MovementTest.VI.Multiline.cs

@@ -178,6 +178,16 @@ public void ViMoveToFirstNonBlankOfLogicalLine_NoOp_OnEmptyLine()
             ));
         }
 
+        [SkippableFact]
+        public void ViDefect2050()
+        {
+            TestSetup(KeyMode.Vi);
+
+            Test("", Keys(
+                _.Escape, _.Underbar
+                ));
+        }
+
         [SkippableFact]
         public void ViMoveToEndOfLine_NoOp_OnEmptyLine()
         {