picocli: Missing default value in ArgGroup.

I understand that by default defaultValue in ArgGroup are not applied.

The behavior is explained at : https://github.com/remkop/picocli/issues/876#issuecomment-558866624 (Note: The default behavior seems surprising to me at first sight but maybe it’s justified)

I faced a situation where it seems that this behavior is not respected (but maybe I missed something) Sorry for the not so short example, I was not able to make it smaller.

The goal is to have this kind of options : X AND ((1A AND 1B) OU (2A OU 2B)) I set default value for X, 2A and 2B. I share the code :

@Command(name = "myCommand",
         mixinStandardHelpOptions = true,
         description = "A command with default value in section ?")
public class Example implements Runnable {

    @ArgGroup(exclusive = false,
              heading = "%n@|italic " //
                      + "Options to be used with group 1 OR group 2 options." //
                      + "|@%n")
    public OptXAndGroupOneOrGroupTwo optXAndGroupOneOrGroupTwo = new OptXAndGroupOneOrGroupTwo();

    public static class OptXAndGroupOneOrGroupTwo {
        @Option(names = { "-x", "--option-x" }, required = true, defaultValue = "Default X", description = "option X")
        private String x;

        @ArgGroup(exclusive = true)
        private OneOrTwo oneORtwo = new OneOrTwo();
    }

    public static class OneOrTwo {

        @ArgGroup(exclusive = false,
                  heading = "%n@|bold Group 1|@ %n%n"//
                          + "@|italic " //
                          + "Description of the group 1 ." //
                          + "|@%n")
        public GroupOne one = new GroupOne();

        @ArgGroup(exclusive = false,
                  heading = "%n@|bold Group 2|@ %n%n"//
                          + "@|italic " //
                          + "Description of the group 2 ." //
                          + "|@%n")
        public GroupTwo two = new GroupTwo();
    }

    public static class GroupOne {
        @Option(names = { "-1a", "--option-1a" },required=true,description = "option A of group 1")
        private String _1a;

        @Option(names = { "-1b", "--option-1b" },required=true,description = "option B of group 1")
        private String _1b;
    }

    public static class GroupTwo {

        @Option(names = { "-2a", "--option-2a" },required=true, defaultValue = "Default 2A", description = "option A of group 2")
        private String _2a;

        
        @Option(names = { "-2b", "--option-2b" },required=true, defaultValue = "Default 2B", description = "option B of group 2")
        private String _2b;
    }

    public void run() {
        System.out.println();
        System.out.println(" X = " + optXAndGroupOneOrGroupTwo.x);
        System.out.println("1A = " + optXAndGroupOneOrGroupTwo.oneORtwo.one._1a);
        System.out.println("1B = " + optXAndGroupOneOrGroupTwo.oneORtwo.one._1b);
        System.out.println("2A = " + optXAndGroupOneOrGroupTwo.oneORtwo.two._2a);
        System.out.println("2B = " + optXAndGroupOneOrGroupTwo.oneORtwo.two._2b);
    }

    public static void main(String... args) {
        Example example = new Example();
        int exitCode = new CommandLine(example).execute(args);

        System.exit(exitCode);
    }
}

When I run my command, it outputs value of each options. E.g if I run it without any options :

 X = Default X
1A = null
1B = null
2A = Default 2A
2B = Default 2B

Now if I run it just with option -x : myCommand -x ANOTHER_VALUE, I get :

 X = ANOTHER_VALUE
1A = null
1B = null
2A = null
2B = null

Default value of 2A and 2B are lost I don’t know if this is expected but this is a surprising behavior.