fixups

Author: jonsequitur

src/System.CommandLine.Suggest.Tests/DotnetSuggestEndToEndTests.cs

@@ -155,7 +155,7 @@ await Process.ExecuteAsync(
 
             stdOut.ToString()
                 .Should()
-                .Be($"--apple{NewLine}--banana{NewLine}--cherry{NewLine}--durian{NewLine}--version{NewLine}");
+                .Be($"/?{NewLine}/h{NewLine}-?{NewLine}--apple{NewLine}--banana{NewLine}--cherry{NewLine}--durian{NewLine}-h{NewLine}--help{NewLine}--version{NewLine}");
         }
     }
 }

src/System.CommandLine.Tests/Help/HelpBuilderTests.cs

@@ -1118,7 +1118,37 @@ public void Help_option_is_shown_in_help()
             var help = _console.Out.ToString();
 
             help.Should()
-                .Contain($"--help{_columnPadding}Show help and usage information");
+                .Contain($"-?, -h, --help{_columnPadding}Show help and usage information");
+        }
+
+        [Fact]
+        public void Options_aliases_differing_only_by_prefix_are_deduplicated_favoring_dashed_prefixes()
+        {
+            var command = new RootCommand
+            {
+                new Option(new[] { "-x", "/x" })
+            };
+
+            _helpBuilder.Write(command);
+            
+            var help = _console.Out.ToString();
+
+            help.Should().NotContain("/x");
+        }
+        
+        [Fact]
+        public void Options_aliases_differing_only_by_prefix_are_deduplicated_favoring_double_dashed_prefixes()
+        {
+            var command = new RootCommand
+            {
+                new Option(new[] { "--long", "/long" })
+            };
+
+            _helpBuilder.Write(command);
+            
+            var help = _console.Out.ToString();
+
+            help.Should().NotContain("/long");
         }
 
         #endregion Options

src/System.CommandLine.Tests/UseHelpTests.cs

@@ -110,7 +110,7 @@ public async Task UseHelp_does_not_display_when_option_defined_with_same_alias()
         public void There_are_no_parse_errors_when_help_is_invoked_on_root_command()
         {
             var parser = new CommandLineBuilder()
-                .UseDefaults()
+                .UseHelp()
                 .Build();
 
             var result = parser.Parse("-h");
@@ -129,7 +129,7 @@ public void There_are_no_parse_errors_when_help_is_invoked_on_subcommand()
             };
 
             var parser = new CommandLineBuilder(command)
-                         .UseDefaults()
+                         .UseHelp()
                          .Build();
 
             var result = parser.Parse("subcommand -h");

src/System.CommandLine/Help/HelpBuilder.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.CommandLine.IO;
+using System.CommandLine.Parsing;
 using System.Linq;
 using System.Text;
 using System.Text.RegularExpressions;
@@ -331,8 +332,14 @@ protected virtual string ArgumentDescriptor(IArgument argument)
         /// <returns>A new <see cref="HelpItem"/></returns>
         private IEnumerable<HelpItem> GetOptionHelpItems(ISymbol symbol)
         {
-            var rawAliases = symbol.RawAliases
-                .OrderBy(alias => alias.Length);
+            var rawAliases = symbol
+                             .RawAliases
+                             .Select(r => r.SplitPrefix())
+                             .OrderBy(r => r.alias)
+                             .ThenBy(r => r.prefix)
+                             .GroupBy(t => t.alias)
+                             .Select(t => t.First())
+                             .Select(t => $"{t.prefix}{t.alias}");
 
             var invocation = string.Join(", ", rawAliases);
 

src/System.CommandLine/Parsing/StringExtensions.cs

@@ -23,17 +23,30 @@ internal static bool ContainsCaseInsensitive(
                                 value ?? "",
                                 CompareOptions.OrdinalIgnoreCase) >= 0;
 
-        internal static string RemovePrefix(this string option)
+        internal static string RemovePrefix(this string rawAlias)
         {
             foreach (var prefix in _optionPrefixStrings)
             {
-                if (option.StartsWith(prefix))
+                if (rawAlias.StartsWith(prefix))
                 {
-                    return option.Substring(prefix.Length);
+                    return rawAlias.Substring(prefix.Length);
                 }
             }
 
-            return option;
+            return rawAlias;
+        }
+
+        internal static (string prefix, string alias) SplitPrefix(this string rawAlias)
+        {
+            foreach (var prefix in _optionPrefixStrings)
+            {
+                if (rawAlias.StartsWith(prefix))
+                {
+                    return (prefix, rawAlias.Substring(prefix.Length));
+                }
+            }
+
+            return (null, rawAlias);
         }
 
         internal static TokenizeResult Tokenize(
@@ -171,9 +184,10 @@ bool CanBeUnbundled(string arg, out IEnumerable<string> replacement)
                     return false;
                 }
 
-                return arg.StartsWith("-") &&
-                       !arg.StartsWith("--") &&
-                       TryUnbundle(arg.RemovePrefix(), out replacement);
+                var (prefix, alias) = arg.SplitPrefix();
+
+                return prefix == "-" && 
+                       TryUnbundle(alias, out replacement);
 
                 Token TokenForOptionAlias(char c) =>
                     argumentDelimiters.Contains(c)