Provide a Default Help Option
emorydunn opened this issue · 4 comments
I'm starting a new project that was prototyped in Python, and one of the differences I noticed between Python's ArgParse and CommandLine is the lack of a default help flag.
To me, at least, having a a help flag included by default would be useful as most applications would benefit from having a simple -h, --help to provide usage and, for the most part, the what the flag needs to do doesn't change (borrowing from ArgParse's help message): "show this help message and exit".
I made made some modifications to my local repo:
- Added
CommandLine.addHelp(option: BoolOption? = nil)to add a default help option, or override with a custom one. This sets._helpOption. - Updated
.parse()to throw a new.HelpOptionerror. This follows my expected behavior where usage info is printed and then exits. - Added a
CommandLine.descriptionthat is used as the error description
I'm still messing around with the updates, but am planning on making a pull request if people think it's a good idea.
My own todo list on this is possibly integrate the description and/ or overriding the default help option into the CommandLine init.
@emorydunn That sounds like a nice improvement! I'm not quite sure about throwing an error from parse() though; what benefit does that bring over just having parse() call printUsage() and exiting?
There are a few reasons for having parse() throw an error:
- Use the exit mechanism already in place (catching an error on parse, printing usage, and exiting)
- To provide the
CommandLine.descriptionin place of an error description (e.g. missing required arguments) in the output. - It required minimal changes to get the desired result
Of course, that may not be the best way to do this.
Edit: I've properly forked and uploaded my changes, so you can take a look.
Another good reason to throw the error would be that it enables use cases where the app is to continue following the help output.