Need help with options that may or may not have a parameter value

[sean-neeley]

I have the following code that correctly outputs this usage message:
Usage: test [-hV] [-y[=FILE]] USERNAME

I would like to be able to run it one of two ways: with arguments '-y USERNAME' and '-y=FILE USERNAME'. However '-y USERNAME' is treated as '-y=USERNAME' (which I do not want) and gives a syntax error, when instead I want it to be equivalent to '-y=blank USERNAME'. Can I have '=' be the only command separator instead of both space and '='? Or is there another solution to this? Thanks.

import picocli.CommandLine;
import picocli.CommandLine.Command;
import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;

import java.util.concurrent.Callable;

@Command(name = "test", mixinStandardHelpOptions = true, version = "1.0", description = "Test program.")
class Test implements Callable<Integer> {

    @Option(names = { "-y" },
    		paramLabel = "FILE",
    		arity = "0..1",
    		fallbackValue = "blank", 
    		description = "Do task with optional input file.")
    private String keyExchangeFile;

    @Parameters(index = "0", 
    		description = "User name", 
    		paramLabel="USERNAME", 
    		arity = "1") 
    private String userName;
    
    @Override
    public Integer call() throws Exception { 
    	// your business logic goes here...
        return 0;
    }

    public static void main(String... args) {
        CommandLine cmd = new CommandLine(new Test());
    	cmd.setSeparator("=");
        int exitCode = cmd.execute(args);
        System.exit(exitCode);
    }
}

[remkop]

This is a common problem for options that have an optional value.
Please see this documentation on Optional Parameter Limitations in the user manual.

Your best solution may be to use the example IParameterPreprocessor from the user manual in your application.
That preprocessor implementation customizes the parser, such that VALUE in --option=VALUE is interpreted as the option parameter, and in --option VALUE (without the = separator), VALUE is interpreted as the positional parameter.
I believe this is exactly what you are looking for.

[sean-neeley]

Thank you, that is the exact issue I'm running into and that example is perfect. Somehow I missed it in the documentation. I appreciate the help!