Option attribute based upon enum does not allow to override validation behaviour

Maybe not a bug, but I have this enum for an option, and when provided with an invalid enum, I do see the standard error message. However, I want to be able to provide or:

• my custom validation message
• ShowHelp()

Please note that in my case I just run CommandLineApplication.Execute<GeneratorCommand>(args); so I have to access to the CommandLineApplication instance to subscribe to ValidationErrorHandler

[stefandevo]

Great! Thanks for this quick feedback!

[natemcmaster]

Not from inside the parsers. There is no application in the context of IValueParser.Parse. The expected way to implement this API is to parse or throw FormatException.

If you want to call ShowHelp, I’d recommend catching CommandParsingException at the top level. Give this a try:

var app = new CommandLineApplication<GeneratorCommand>();
app.Conventions.UseDefaultConventions();
try
{
   app.Execute(args);
}
catch (CommandParsingException ex)
{
  Console.Error.WriteLine(ex.Message);
  app.ShowHelp();
}

As you can see in the implementation, CommandLineApplication.Execute<T>(args) doesn’t do much more than this. https://github.com/natemcmaster/CommandLineUtils/blob/ecfc8bc3992f9ee899115622dcb851d0274f3557/src/CommandLineUtils/CommandLineApplication.Execute.cs#L51-L64