fix #1533

Author: jonsequitur

src/System.CommandLine.Tests/ParserTests.cs

@@ -1685,6 +1685,27 @@ public void A_subcommand_wont_overflow_when_checking_maximum_argument_capcity()
             act.Should().NotThrow();
         }
 
+        [Fact] // https://github.com/dotnet/command-line-api/issues/1533
+        public void Empty_strings_in_parsed_args_array_are_ignored()
+        {
+            var option = new Option<int>("-x");
+            var subcommand = new Command("sub")
+            {
+                option
+            };
+            var command = new RootCommand
+            {
+                subcommand
+            };
+
+            var result = command.Parse("", "sub", "", "-x", "123");
+
+            result.Errors.Should().BeEmpty();
+
+            result.CommandResult.Command.Should().Be(subcommand);
+            result.FindResultFor(option).Should().NotBeNull();
+        }
+
         [TypeConverter(typeof(CustomTypeConverter))]
         public class ClassWithCustomTypeConverter
         {

src/System.CommandLine/Parsing/StringExtensions.cs

@@ -36,7 +36,6 @@ internal static string RemovePrefix(this string alias)
 
         internal static int GetPrefixLength(this string alias)
         {
-            // empty aliases are illegal, so there is no need to check for length
             if (alias[0] == '-')
                 return alias.Length > 1 && alias[1] == '-' ? 2 : 1;
             if (alias[0] == '/')
@@ -76,7 +75,7 @@ internal static TokenizeResult Tokenize(
             for (var i = 0; i < argList.Count; i++)
             {
                 var arg = argList[i];
-
+                
                 if (foundDoubleDash)
                 {
                     if (configuration.EnableLegacyDoubleDashBehavior)
@@ -200,7 +199,7 @@ internal static TokenizeResult Tokenize(
                         tokenList.Add(Argument(arg));
                     }
                 }
-                else
+                else if (arg.Length > 0)
                 {
                     tokenList.Add(Argument(arg));
                 }