Ideas for possible some improvements

[Rast1234]

Hello. I am writing an utility and i decided to use your library. Right now i have 4 issues and maybe something can be improved, if you'd like:

1. The idea of commands is very nice. However, right now i can't have multiple commands and run one command by default (when no args specified). Yes, this might be cryptic for users, but it's normal behavior for GUI apps (like Process Explorer and other Sysinternals tools): it runs normally by default, but if you pass args, it displays help in MessageBox or does what args tell it to do.
   Right now i'm using this hack:

   • if there are no args
   • or if there are args, and if first arg is not a command (checking by using copy of private static GetMatchingCommand because it's private!)
   • and arg[0] is not help
   • then insert name of default command to args[0]
   • then let your library do all the job like normal

   So i think you can add an optional argument to DispatchCommand or add metadata field to command to allow some command run as default one.

2. As i mentioned, i'm writing a GUI app. I don't need int return code, and my main has void return type. If everything was ok, app does nothing, otherwise it displays a MessageBox with message and icon. However, can't return more than int from a command. Right now i just have public static MyResult Result {get; set;} field in Program class and set it from commands which is obviously too ugly. Maybe you can introduce generic ConsoleCommand<T> to allow users to return any type?

3. I have strange behavior with setting default value for optional argument. If i don't specify the value, it is null every time. Maybe that's intended, but i expected from docs that Action gets called and i can check for null and set default value from there. For example:

   HasOption("c|config:", "Config file", x => ConfigFileName = x ?? "test");
   

   ConfigFileName is not set from this Action, i need to back it up with default value elsewhere.

4. I can't get : or = in prototype to show default value instead of VALUE. Like in example above, i have in generated help: -c, --config[=VALUE] Config file. Am i missing something? I'd like it to be -c, --config[=test] Config file but when i specify "c|config:test", i gen an exception.

[fschwiet]

For 3 and 4, I don't think there is a mechanism to have it show you're default value in place of "[=VALUE]" in the help text. You can mention the default value in the option description if you want to inform the user (see example below).

But generally if a option is optional (in the sense that I think of it being optional, there is a second sense I'll get back to) I do something like:

public class MattsCommand : ConsoleCommand
{
    public string Baz = "foobarbaz";

    public MattsCommand()
    {
        this.IsCommand("matts");
        this.HasOption("b|baz=", "baz parameter (default value is foorbarbaz)", v => Baz = v);
    }
    public override int Run(string[] remainingArguments)
    {
        Console.WriteLine("baz is " + Baz);
        return 0;
    }

In this case, the user might choose not to specify "-b" in which case baz will have the value "foobarbaz". The lambda expression v => Baz = v only runs if the command line expression contains a '-b'. If its included multiple times, the lambda is called multiple times. If it is never included, the lambda is never called. This is one kind of "optional". To make something non-optional in this regard, you use HasRequiredOption instead of HasOption. Then the user will get a failure with descriptive text if they do not specify "-b value", and setting the default "foobarbaz" is unnecessary.

The second sense of optionalness is when you use the ':' as in HasOption("b:", "....", x => ...). In this case, again, the lambda only runs if -b is specified in the command line. But in this case, the user might not include a value afterwards and just pass in '-b' (and the lambda will be passed null). I honestly haven't used this approach, its inherited from NDesk.Forms. But I imagine it might look something like:

public class MattsCommand : ConsoleCommand
{
    public string Baz = null;

    public MattsCommand()
    {
        this.IsCommand("matts");
        this.HasOption("b|baz:", "baz parameter (default value is foorbarbaz)", v => Baz = v ?? "foobarbaz");
    }
    public override int Run(string[] remainingArguments)
    {
        if (Baz != null) {
            Console.WriteLine("Doing the optional baz thing with parameter " + Baz);
        } else {
            Console.WriteLine("Not going to baz this time.");
        }
        return 0;
     }
}

Here we set the class property to null, for the default parameter of not doing any kind of baz operation. If the user specifies -b, then they get the baz operation with a default value. If they pass in '-b value' then baz runs with parameter value. If they don't specify -b, then the else branch runs. I haven't actually tried/use this aspect of NDesk.Options.