FileSystemInfo[] Argument type not parsing in preview4

[brandonh-msft]

I was previously using preview1 of this project and had this code

AddArgument(new Argument<FileSystemInfo[]>("files-or-directories", LocalizedStrings.BinaryAnalysisContentHelp)
{
    Arity = ArgumentArity.OneOrMore,
}.ExistingOnly());

which worked as desired, however now it is throwing me an exception:

Unhandled exception: System.ArgumentException: Type System.Collections.Generic.IReadOnlyCollection`1[System.IO.FileSystemInfo] cannot be created without a custom binder.
   at System.CommandLine.Binding.ArgumentConverter.CreateEnumerable(Type type, Type itemType, Int32 capacity)

[jonsequitur]

I wasn't able to reproduce this. Could you provide a more detailed repro?

Here's what I tried:

[brandonh-msft]

In the case where I see problems, I am passing in . as the argument to my command. As I said this used to work w/o issue to get a FileSystemInfo set that pointed just to the current directory. Maybe that's the edge case? Otherwise not sure what more to try; I definitely get an exception using the latest stuff 🤷🏻‍♂️

[brandonh-msft]

Here's a more complete sample. Of special note is that I am using the System.CommandLine.NamingConventionBinder pkg and namespace to accomodate our implementation of setting the .Handler property on the commands within the constructor. (Changing to the new .SetHandler() approach would've been too much churn for the bug I was trying to solve).

If you want to inspect the file before/after my change it can be found here.

public ConsoleAnalyzeBinariesCommand()
{
    Handler = CommandHandler.Create<ParseResult, ConsoleAnalyzeBinariesCommandOptions, CancellationToken>((result, options, token) =>
        Host.CreateDefaultBuilder()
            .ConfigureServices(services => services.AddSingleton<IBinaryAnalysisExecutorOptions>(options))
            .UseConsoleUpgradeAssistant<ConsoleAnalyzeBinaries>(options, result)
            .RunUpgradeAssistantAsync(token));

    AddArgument(new Argument<FileSystemInfo[]>("files-or-directories", /* REQUIRED FOR preview4 parse: r =>
    {
        if (r?.Tokens is null || !r.Tokens.Any())
        {
            throw new ArgumentException(@"Must specify target file/directory for analysis");
        }

        return r.Tokens.Select<Token, FileSystemInfo?>(i =>
        {
            var path = i.Value;
            if (string.IsNullOrEmpty(path))
            {
                return default;
            }

            if (Directory.Exists(path))
            {
                return new DirectoryInfo(path);
            }
            else if (path.EndsWith(Path.DirectorySeparatorChar.ToString(), StringComparison.Ordinal) ||
                     path.EndsWith(Path.AltDirectorySeparatorChar.ToString(), StringComparison.Ordinal))
            {
                return new DirectoryInfo(path);
            }
            else
            {
                return new FileInfo(path);
            }
        }).Where(i => i is not null).Cast<FileSystemInfo>().ToArray();
    },*/ description: LocalizedStrings.BinaryAnalysisContentHelp)
    {
        Arity = ArgumentArity.OneOrMore,
    }.ExistingOnly());
}