subcommand help flags cause exception

When trying to use a help flag on a subcommand, I get an Unhandled Exception: System.InvalidOperationException: Sequence contains more than one matching element error.

Example code:

using System;
using McMaster.Extensions.CommandLineUtils;

namespace updater
{
    class Program
    {
        public static int Main(string[] args)
        {
            var app = new CommandLineApplication();
            app.Name = "updater";
            app.HelpOption(inherited: true);

            app.Command("get", (getcmd) =>
            {
                getcmd.Description = "Gets a list of things.";
                getcmd.HelpOption();
                
                getcmd.OnExecute(() =>
                {
                    getcmd.ShowHelp();
                    return 1;
                });
            });

            app.OnExecute(() => {
                app.ShowHelp();
                return 1;
            });

            return app.Execute(args);
        }
    }
}

Here are the steps I am taking to create this:

• > dotnet publish --self-contained -r win10-x64
• > .\bin\Debug\netcoreapp2.0\win10-x64\publish\updater.exe get
• > .\bin\Debug\netcoreapp2.0\win10-x64\publish\updater.exe get --help

It throws this exception:

Unhandled Exception: System.InvalidOperationException: Sequence contains more than one matching element
   at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source, Func`2 predicate)
   at McMaster.Extensions.CommandLineUtils.CommandLineProcessor.ProcessOption() in C:\projects\commandlineutils\src\CommandLineUtils\Internal\CommandLineProcessor.cs:line 156
   at McMaster.Extensions.CommandLineUtils.CommandLineProcessor.ProcessNext() in C:\projects\commandlineutils\src\CommandLineUtils\Internal\CommandLineProcessor.cs:line 62
   at McMaster.Extensions.CommandLineUtils.CommandLineProcessor.Process() in C:\projects\commandlineutils\src\CommandLineUtils\Internal\CommandLineProcessor.cs:line 35
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.Parse(String[] args) in C:\projects\commandlineutils\src\CommandLineUtils\CommandLineApplication.cs:line 532
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[] args) in C:\projects\commandlineutils\src\CommandLineUtils\CommandLineApplication.cs:line 597
   at updater.Program.Main(String[] args) in P:\C#\updater\Program.cs:line 31

Here is my dotnet configuration:

> dotnet --info
.NET Command Line Tools (2.1.2)

Product Information:
 Version:            2.1.2
 Commit SHA-1 hash:  5695315371

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.16299
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.1.2\

Microsoft .NET Core Shared Framework Host

  Version  : 2.0.5
  Build    : 17373eb129b3b05aa18ece963f8795d65ef8ea54

I very well could be doing something wrong, too.

[natemcmaster]

@mxplusb the simplest fix here for you is to only have one call to .HelpOption. If you call app.HelpOption(inherited: true) on your top level command, you don’t need to call .HelpOption on any of the subcommand objects.

             app.Command("get", (getcmd) =>
             {
                 getcmd.Description = "Gets a list of things.";
-                getcmd.HelpOption();
                
                 getcmd.OnExecute(() =>
                 {
                     getcmd.ShowHelp();

[natemcmaster]

Thanks @handcraftedsource! Yes, this is a good place to start.