fix #1157

Author: jonsequitur

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

@@ -5,6 +5,7 @@
 using System.Collections.Generic;
 using System.CommandLine.Builder;
 using System.CommandLine.Help;
+using System.CommandLine.Invocation;
 using System.CommandLine.IO;
 using System.CommandLine.Parsing;
 using System.IO;
@@ -668,7 +669,7 @@ public void Arguments_section_properly_wraps()
             var name = "argument-name-for-a-command-that-is-long-enough-to-wrap-to-a-new-line";
             var description = "Argument description for a command with line breaks that is long enough to wrap to a new line.";
 
-            var command = new RootCommand()
+            var command = new RootCommand
             {
                 new Argument
                 {
@@ -690,33 +691,6 @@ public void Arguments_section_properly_wraps()
             _console.Out.ToString().Should().Contain(expected);
         }
 
-        [Theory]
-        [InlineData(typeof(bool))]
-        [InlineData(typeof(bool?))]
-        public void Command_argument_descriptor_is_empty_for_boolean_values(Type type)
-        {
-            var description = "This is the argument description";
-
-            var command = new Command("outer", "Help text for the outer command")
-            {
-                new Argument
-                {
-                    Description = description,
-                    ArgumentType = type
-                }
-            };
-
-            HelpBuilder helpBuilder = GetHelpBuilder(SmallMaxWidth);
-
-            helpBuilder.Write(command);
-
-            var expected =
-                $"Arguments:{NewLine}" +
-                $"{_indentation}{_columnPadding}{description}";
-
-            _console.Out.ToString().Should().Contain(expected);
-        }
-
         [Theory]
         [InlineData(typeof(FileAccess))]
         [InlineData(typeof(FileAccess?))]
@@ -764,6 +738,27 @@ public void Option_argument_descriptor_is_empty_for_boolean_values(Type type)
             _console.Out.ToString().Should().Contain($"--opt{_columnPadding}{description}");
         }
 
+        [Fact] // https://github.com/dotnet/command-line-api/issues/1157
+        public void Command_arguments_show_argument_name_as_descriptor()
+        {
+            var command = new RootCommand
+            {
+                new Argument<bool>("boolArgument", "Some value"),
+                new Argument<int>("intArgument", "Another value"),
+            };
+            
+            var helpBuilder = GetHelpBuilder(SmallMaxWidth);
+
+            helpBuilder.Write(command);
+
+            var expected =
+                $"Arguments:{NewLine}" +
+                $"{_indentation}<boolArgument>{_columnPadding}Some value{NewLine}" +
+                $"{_indentation}<intArgument> {_columnPadding}Another value{NewLine}";
+
+            _console.Out.ToString().Should().Contain(expected);
+        }
+
         [Theory]
         [InlineData(typeof(FileAccess))]
         [InlineData(typeof(FileAccess?))]
@@ -878,7 +873,7 @@ public void Command_arguments_can_customize_default_value()
         }
 
         [Fact]
-        public void Command_arguments_can_customize_dedescriptor()
+        public void Command_arguments_can_customize_descriptor()
         {
             var argument = new Argument<string>("some-arg", getDefaultValue: () => "not 42");
             var command = new Command("the-command", "command help")

src/System.CommandLine/Help/HelpBuilder.cs

@@ -134,10 +134,10 @@ protected IEnumerable<HelpItem> GetCommandArguments(ICommand command)
                     .SelectMany(GetArguments)
                     .Distinct();
 
-
             IEnumerable<HelpItem> GetArguments(ICommand command)
             {
                 var arguments = command.Arguments.Where(x => !x.IsHidden).ToList();
+
                 foreach (IArgument argument in arguments)
                 {
                     string argumentDescriptor = GetArgumentDescriptor(argument);
@@ -286,7 +286,11 @@ bool IsOptional(IArgument argument) =>
 
         protected void RenderAsColumns(params HelpItem[] items)
         {
-            if (items.Length == 0) return;
+            if (items.Length == 0)
+            {
+                return;
+            }
+
             int windowWidth = MaxWidth;
 
             int firstColumnWidth = items.Select(x => x.Descriptor.Length).Max();
@@ -338,9 +342,13 @@ protected void RenderAsColumns(params HelpItem[] items)
 
         private static IEnumerable<string> WrapItem(string item, int maxWidth)
         {
-            if (string.IsNullOrWhiteSpace(item)) yield break;
+            if (string.IsNullOrWhiteSpace(item))
+            {
+                yield break;
+            }
+
             //First handle existing new lines
-            var parts = item.Split(new string[] { "\r\n", "\n", }, StringSplitOptions.None);
+            var parts = item.Split(new[] { "\r\n", "\n" }, StringSplitOptions.None);
 
             foreach (string part in parts)
             {
@@ -499,7 +507,14 @@ protected string GetArgumentDescriptor(IArgument argument)
             if (argument.ValueType == typeof(bool) ||
                 argument.ValueType == typeof(bool?))
             {
-                return "";
+                if (argument.Parents.FirstOrDefault() is ICommand)
+                {
+                    return $"<{argument.Name}>";
+                }
+                else
+                {
+                    return "";
+                }
             }
 
             string descriptor;