Fix issue with extra spaces in commands (#366) (#369)

(cherry picked from commit d0a5110)

src/Microsoft.Repl/Parsing/CoreParser.cs

@@ -14,6 +14,9 @@ public ICoreParseResult Parse(string commandText, int caretPosition)
             commandText = commandText ?? throw new ArgumentNullException(nameof(commandText));
 
             List<string> sections = commandText.Split(' ').ToList();
+            // We can't use StringSplitOptions.RemoveEmptyEntries because it
+            // is more aggressive than we need, so we need to do it ourselves.
+            RemoveEmptyEntries(sections);
             Dictionary<int, int> sectionStartLookup = new Dictionary<int, int>();
             HashSet<int> quotedSections = new HashSet<int>();
             int runningIndex = 0;
@@ -131,5 +134,23 @@ public ICoreParseResult Parse(string commandText, int caretPosition)
 
             return new CoreParseResult(caretPosition, caretPositionWithinSelectedSection, commandText, sections, selectedSection, sectionStartLookup, quotedSections);
         }
+
+        private static void RemoveEmptyEntries(List<string> sections)
+        {
+            if (sections.Count < 2)
+            {
+                return;
+            }
+
+            // We want to remove empty spaces from the beginning, and from the middle
+            // but not from the end.
+            for (int index = 0; index < sections.Count - 1; index++)
+            {
+                if (sections[index].Length == 0)
+                {
+                    sections.RemoveAt(index);
+                }
+            }
+        }
     }
 }

test/Microsoft.Repl.Tests/Parsing/CoreParseResultTests.cs

@@ -80,5 +80,20 @@ public void Slice_WithSelectedSection_SelectedSectionMoves(string commandText, i
 
             Assert.Equal(expectedSelectedSection, result.SelectedSection);
         }
+
+        [Theory]
+        [InlineData("set base  https://localhost", 3)]
+        [InlineData("run  c:\\script.txt", 2)]
+        [InlineData("help  connect", 2)]
+        [InlineData("set base ", 3)]
+        [InlineData("", 1)]
+        [InlineData(" set base https://localhost", 3)]
+        public void Parse_WithDoubleSpace_RemovesEmptySections(string commandText, int expectedSectionCount)
+        {
+            CoreParser parser = new CoreParser();
+            ICoreParseResult parseResult = parser.Parse(commandText, commandText.Length + 1);
+
+            Assert.Equal(expectedSectionCount, parseResult.Sections.Count);
+        }
     }
 }