Issue with OptionParser#printHelpOn()

Dheeraj Khardwal

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Apr 6, 2016, 10:31:21 AM4/6/16

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Pardon me if this is naive.

I'm getting an issue - which I'm not getting quite properly - while printing help multiple times based on user input.

Please see below snippet for my implementation and output as well.

import java.io.IOException;
import java.util.Random;
import java.util.Scanner;

import joptsimple.OptionParser;
import joptsimple.OptionSet;

public class CommandLine {

	private OptionParser parser;
	private Random random;

	private void init() throws IOException {
		random = new Random();
		parser = new OptionParser() {
			{
				accepts("n", "next random number");
				accepts("q", "quit");
				accepts("h", "show help").isForHelp();
			}
		};
		
		parser.printHelpOn(System.out);
	}
	
	private boolean handle(String[] args) throws IOException {
		OptionSet opts = parser.parse(args);
		
		if(opts.has("n")) {
			System.out.println(random.nextInt());
		}else if(opts.has("h")) {
			parser.printHelpOn(System.out);
		} else if(opts.has("q")) {
			System.out.println("Bye.");
			return true;
		}
		
		return false;
	}

	public static void main(String[] args) throws IOException {
		CommandLine commander = new CommandLine();
		commander.init();
		Scanner sc = null;
		try {
			sc = new Scanner(System.in);
			for (prompt(); sc.hasNextLine(); prompt()) {
				String line = sc.nextLine().replaceAll("\n", "");
				
				// return pressed
				if (line.length() == 0) {
					System.out.println("No option selected. Use -h to get help.");
					continue;
				}

				// split line into arguments
				boolean exit = commander.handle(line.split(" "));
				if(exit)
					break;
			}
		} finally {
			sc.close();
		}
	}
	
	private static void prompt() {
		System.out.print(">> ");
	}

}

And the output:

Option  Description       
------  -----------       
-h      show help         
-n      next random number
-q      quit              
>> -n
-1307682825
>> -n
-282704935
>> -h
Option  Description       
------  -----------       
-h      show help         
-n      next random number
-q      quit              
Option  Description       
------  -----------       
-h      show help         
-n      next random number
-q      quit              
>> -h
Option  Description       
------  -----------       
-h      show help         
-n      next random number
-q      quit              
Option  Description       
------  -----------       
-h      show help         
-n      next random number
-q      quit              
Option  Description       
------  -----------       
-h      show help         
-n      next random number
-q      quit              
>> -q
Bye.

Please tell me how can I get around this.

Paul Holser

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Apr 6, 2016, 11:41:18 AM4/6/16

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Hi Dheeraj,

Thanks for your interest in jopt-simple!

It appears that BuiltinHelpFormatter.format() wasn't ever expecting to be called more than once on a given instance. It's building up its output cumulatively on every call to format().

I'll add a GitHub issue for this, so that every time OptionParser.printHelpOn() is called and delegates to a BuiltinHelpFormatter, its cumulative output is cleared before building it up fresh.

Appreciate it!

--p

Dheeraj Khardwal

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Apr 6, 2016, 2:26:52 PM4/6/16

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Hi Paul,

First of all, many thanks for creating this library. :)

And thanks for taking this issue up.

Yes, I just looked up the issue on github (sorry I posted here instead of raising the issue there).
Looking forward for contributing to jopts. :)