Using Picocli, how do I require a positional argument and then optional arguments depending on the value of the positional argument

I have a situation where I need to have three mandatory arguments (field1, field2 and field3. I then want the user to enter a command name (mandatory, values can be create, list, etc). The command name must be entered, and must be singular (only one of them can be entered).

Some of the commands will have arguments, some of them will not. How do I handle that?

I tried the following, but I get an error:

ArgGroup has no options or positional parameters, and no subgroups

public class CliParserArgs {
    @Option(names = {"--field1"}, required = true)
    private String field1;

    @Option(names = {"--field2"}, required = true)
    String field2;

    @Option(names={"--field3"}, required = true)
    String field3;

    @Option(names = {"-h", "--help"}, usageHelp = true) boolean help;

    class Create {
        private final String val;
        public Create(final String val) {
            this.val = val;
        }
    }

    class ListObjects {
        private final String val;
        public ListObjects(final String val) {
            this.val = val;
        }
    }

    @ArgGroup(heading = "Command", exclusive = true, multiplicity = "1")
    Create create;
    ListObjects listObjects;

    public static void main(String[] args) {
        CliParserArgs cliParserArgs = new CliParserArgs();
        CommandLine cmd = new CommandLine(cliParserArgs);
        CommandLine.ParseResult parseResult = cmd.parseArgs(args);
        System.err.println("parse results: " + parseResult.matchedArgs().toString());

        try {
        if (cmd.isUsageHelpRequested()) {
            cmd.usage(System.out);
        }
        } catch (CommandLine.ParameterException e) {
            System.err.println("error: " + e.getMessage());
            System.err.println(e.getStackTrace());

        }
    }
}

[deining]

Having a look at your code, I realise that none of your classes has a @Command annonation. These annotations are used to declare classes as commands. This is not only true for the main command, but also for subcommands. And yes, derived from your description, I guess subcommands are what you are looking for. Please have a look at the Subcommands documentation. Also the picocli codebase has a minimal working example on subcommands.

Hopefully, the code below will do what you need:

package test;

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

public class CliParserArgs {

    @Command(subcommands = { Create.class, ListObjects.class,
            CommandLine.HelpCommand.class }, name = "MyCommand", mixinStandardHelpOptions = true, version = "x.xx")
    static class CliParserCommand implements Runnable {
        @Option(names = { "--field1" }, required = true)
        private String field1;

        @Option(names = { "--field2" }, required = true)
        String field2;

        @Option(names = { "--field3" }, required = true)
        String field3;

        @Override
        public void run() {
            // nothing to do here
        }
    }

    public static void main(String[] args) {
        CommandLine cmd = new CommandLine(new CliParserCommand());
        int exitCode = cmd.execute(args);
        System.exit(exitCode);
    }
}

@Command(name = "subCreate")
class Create implements Runnable {

    @Option(names = { "-f", "--file" })
    String val;

    @Override
    public void run() {
        // Do whatever create is supposed to do
    }
}

@Command(name = "subListObjects")
class ListObjects implements Runnable {

    @Option(names = { "-v", "--value" })
    String val;

    @Override
    public void run() {
        // Do whatever listobjects is supposed to do
    }
}

I hope this example can serve as a starting point. Don’t hesitate to ask again once you have further questions!

[remkop]

Great, thank you!