Duplicate "--version" keys

[mmckechney]

After updating to the latest release (System.CommandLine v2.0.0-beta3.22114.1), I am now getting the following error at runtime:

Unhandled exception. System.ArgumentException: An item with the same key has already been added. Key: --version
   at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
   at System.CommandLine.Parsing.StringExtensions.ValidTokens(Command command)
   at System.CommandLine.Parsing.StringExtensions.Tokenize(IReadOnlyList`1 args, CommandLineConfiguration configuration)
   at System.CommandLine.Parsing.Parser.Parse(IReadOnlyList`1 arguments, String rawInput)
   at System.CommandLine.CommandExtensions.GetDefaultInvocationPipeline(Command command, String[] args)
   at System.CommandLine.CommandExtensions.InvokeAsync(Command command, String[] args, IConsole console)

No other changes were made to the app that was previously working. I do use System.CommandLine.NamingConventionBinder to be compatible with the older CommandHandler.Create model, could this be the problem?

[jonsequitur]

Can you provide a code sample to reproduce this?

[mmckechney]

Full sample code can be found here: https://gist.github.com/mmckechney/7bd92a4417458fb8b919b44bac5c5b89

In creating this sample I discovered the root of the problem: The use of the CommandLineBuilder to add additional help context breaks when you include UseDefaults() with the latest Beta3 release.

//This throws exception with: "One or more errors occurred. (An item with the same key has already been added. Key: --version)'"
  var parser = new CommandLineBuilder(rootCommand)
                .UseDefaults()
                .UseHelp(ctx =>
                {
                    ctx.HelpBuilder.CustomizeLayout(_ => System.CommandLine.Help.HelpBuilder.Default
                                             .GetLayout()
                                             .Prepend(
                                                 _ => _.Output.WriteLine("**Adding extra help here**")
                                             ));
                }).Build();

However: I also noticed that if you remove the UseDefaults(), the program runs, but Prepend help text does not get displayed. Is there a new method to prepend to your help message or is this a bug?

//This runs, but the help output is not modified as expected
  var parser = new CommandLineBuilder(rootCommand)
                .UseHelp(ctx =>
                {
                    ctx.HelpBuilder.CustomizeLayout(_ => System.CommandLine.Help.HelpBuilder.Default
                                             .Prepend(
                                                 _ => _.Output.WriteLine("**Adding extra help here**")
                                             ));
                }).Build();

[zachgharst]

Is there an update on this other than the milestone tag? Do we have any way to work around this? I'm experiencing the same problem. I just want to add a logo and copyright before description.

[jonsequitur]

I'm not seeing this issue when calling Invoke on the Parser returned from CommandLineBuilder.Build.

I do see it when I call Invoke directly on the RootCommand.

That should allow people to work around this while we sort out the issue.

[perlun]

For reference, this was also spotted by another user some months later: #1791 (comment)

[perlun]

I am running into this in my application, but perhaps for slightly different reasons than the rest of you. I have a custom --version option defined like this (heavily simplified example):

var versionOption = new Option<VoidObject>(new[] { "--version", "-v" }, "Show version information");

var rootCommand = new RootCommand { ... };
rootCommand.AddOption(versionOption);

return new CommandLineBuilder(rootCommand)
    .UseDefaults() // <-- this triggers the problem
    .Build()
    .Invoke(args, console);

Changing from .UseDefaults() to .UseHelp() works in my case (but some of my application's options still causes other exceptions, likely because of some other incompatibility since the upgrade).