Usage section shows Argument.Name rather than Argument.HelpName

[KalleOlaviNiemitalo]

In the help output, the Usage section shows Argument.Name, but the Arguments section shows Argument.HelpName. I think this is inconsistent and they should both use Argument.HelpName if set, so that Argument.Name would be culture-invariant and usable for System.CommandLine.NamingConventionBinder. #1891 (comment)

Demo

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net7.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="System.CommandLine" Version="2.0.0-beta4.22272.1" />
  </ItemGroup>

</Project>

using System.CommandLine;
using System.IO;

var command = new RootCommand()
{
    new Argument<FileInfo>(name: "inputfile")
    {
        HelpName = "inputfile.log",
    },
};

return await command.InvokeAsync(args);

$ dotnet run
Required argument missing for command: 'ArgumentHelpDemo'.

Description:

Usage:
  ArgumentHelpDemo <inputfile> [options]

Arguments:
  <inputfile.log>

Options:
  --version       Show version information
  -?, -h, --help  Show help and usage information

Current implementation

Usage section:

command-line-api/src/System.CommandLine/Help/HelpBuilder.cs

Lines 296 to 304 in 209b724

	if (isOptional)
	{
	sb.Append($"[<{argument.Name}>{arityIndicator}");
	(end ??= new Stack<char>()).Push(']');
	}
	else
	{
	sb.Append($"<{argument.Name}>{arityIndicator}");
	}

Arguments section:

command-line-api/src/System.CommandLine/Help/HelpBuilder.Default.cs

Lines 73 to 87 in 209b724

	var arg = argument;
	var helpName = arg?.HelpName ?? string.Empty;
	if (!string.IsNullOrEmpty(helpName))
	{
	firstColumn = helpName!;
	}
	else if (completions.Length > 0)
	{
	firstColumn = string.Join("|", completions);
	}
	else
	{
	firstColumn = argument.Name;
	}

[KalleOlaviNiemitalo]

This issue is still valid as of commit b4bbdd2 (2023-07-27).