Passing extra arguments after "help (verb)" causes an InvalidOperationException

[rmunn]

Using CommandLineParser 2.0.235.0 beta, I can cause an InvalidOperationException by simply running "my-cmd.exe help verb foo" instead of "my-cmd.exe help verb". "my-cmd.exe help verb" produces the expected help text, but "my-cmd.exe help verb foo" produces the following exception:

Unhandled Exception: System.InvalidOperationException: Sequence contains more than one element
   at System.Linq.Enumerable.SingleOrDefault[TSource](IEnumerable`1 source)
   at CommandLine.Core.InstanceChooser.<>c__DisplayClass0_0.<Choose>b__0()
   at CommandLine.Core.InstanceChooser.Choose(Func`3 tokenizer, IEnumerable`1 types, IEnumerable`1 arguments, StringComparer nameComparer, CultureInfo parsingCulture, IEnumerable`1 nonFatalErrors)
   at CommandLine.Parser.<>c__DisplayClass13_0.<ParseArguments>b__0()
   at CommandLine.Parser.MakeParserResult[T](Func`1 parseFunc, ParserSettings settings)
   at TryOutCommandLineParser.Program.Main(String[] args) in c:\src\try\TryOutCommandLineParser\Program.cs:line 17

Running "my-cmd.exe verb foo --help" works, sort of (I don't like the "Option 'help' is unknown) error, but I can live with it. But I'm pretty sure that users will at one point try replacing "my-cmd.exe verb foo bar -v" with "my-cmd.exe help verb foo bar -v" to get help usage, and I'd like this to be handled. So when the "help" verb is invoked, I'd like it to ignore any further arguments, but not throw an exception if they are present.

[gsscoder]

@rmunn, thanks for detailed reporting, I'll try fix both issues (the exception and help unknown).

I'll update you here.

Thanks, again!

[gsscoder]

When you invoke your app with:

my-cmd.exe verb foo --help

--help is enumerated as an option because the canonical help request, requires you to put "--help" as first argument. In this case the help screen is showed not because you added "--help" but because the command line syntax rules are not respected.

I need reason a little more on this... The main issue anyway is fixed, in seconds I'll merge to master...

[gsscoder]

Version 2.0.239-beta fixes the issue (just released to NuGet), if this works can you please close the issue?

Thanks, @rmunn.

[rmunn]

Regarding --help, the logic I've come to expect from a verb-using command-line program like git is the following:

1. Scan all the arguments (up to the -- argument, if present) for a -h or --help argument.
2. If it was present, display appropriate help for the verb (or, if no verb was present, for the program as a whole).
3. If no -h or --help was present, process the verb's normal arguments.

For example:

$ git pull -v --ff-only --help
usage: [...]

Whereas:

$ git pull -v --ff-only --bad-argument
error: unknown option `bad-argument'
usage: [...]

But the --help argument, and how to treat it, should probably be discussed in a separate issue.

[rmunn]

I've tested version 2.0.239-beta, and it works the way I want now (barring the "Option 'help' is unknown" error). This issue is fixed.

[gsscoder]

@rmunn, after some reasoning I'm agree with you that listing help as unknown option is senseless.

This is now fixed in version 2.0.241-beta on master and released to NuGet.

Anyway an eventual -h will not be removed because, this is not a built-in command for requesting help.

If you're interested in internals:
this is the test -> https://github.com/gsscoder/commandline/blob/master/tests/CommandLine.Tests/Unit/ParserTests.cs#L542
this is the fix -> https://github.com/gsscoder/commandline/blob/master/src/CommandLine/ErrorExtensions.cs#L23

Bye! :)