ExecParameterConsumer implements IParameterConsumer

Find.java

import static org.junit.jupiter.api.Assertions.*;

import java.io.File;
import java.util.LinkedList;
import java.util.List;
import java.util.Set;
import java.util.Stack;

import picocli.CommandLine;
import picocli.CommandLine.IParameterConsumer;
import picocli.CommandLine.Model.ArgSpec;
import picocli.CommandLine.Model.CommandSpec;
import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;

public class Find {

	@Option(names = "-exec", parameterConsumer = ExecParameterConsumer.class)
	public Exec exec;

	@Parameters
	public List<File> arguments;

	public static void main(String[] args) {
		Find find = CommandLine.populateCommand(new Find(), "a.txt", "-exec", "echo", "-n", "{}", ";", "b.txt", "c.txt");
		assertEquals("echo -n {} [;]", find.exec.toString());
		assertEquals("[a.txt, b.txt, c.txt]", find.arguments.toString());

		find = CommandLine.populateCommand(new Find(), "a.txt", "-exec", "echo", "-n", "{}", "+", "b.txt", "c.txt");
		assertEquals("echo -n {} [+]", find.exec.toString());
		assertEquals("[a.txt, b.txt, c.txt]", find.arguments.toString());

		find = CommandLine.populateCommand(new Find(), "-exec", "echo", "-n", "{}");
		assertEquals("echo -n {} [;]", find.exec.toString());

		find = CommandLine.populateCommand(new Find(), "-exec", "echo", "-n", "{}", "+");
		assertEquals("echo -n {} [+]", find.exec.toString());
	}

	public static class Exec {

		public boolean single;
		public String[] command;

		public static final String MARK_SINGLE = ";";
		public static final String MARK_MULTI = "+";

		@Override
		public String toString() {
			return String.format("%s [%s]", String.join(" ", command), single ? MARK_SINGLE : MARK_MULTI);
		}
	}

	public static class ExecParameterConsumer implements IParameterConsumer {

		@Override
		public void consumeParameters(Stack<String> args, ArgSpec argSpec, CommandSpec commandSpec) {
			LinkedList<String> command = new LinkedList<String>();
			Set<String> marker = Set.of(Exec.MARK_SINGLE, Exec.MARK_MULTI);

			while (!args.isEmpty() && (command.isEmpty() || !marker.contains(command.peekLast()))) {
				command.add(args.pop());
			}

			Exec exec = new Exec();

			if (marker.contains(command.peekLast())) {
				exec.single = Exec.MARK_SINGLE.equals(command.removeLast());
				exec.command = command.toArray(new String[0]);
			} else {
				exec.single = true;
				exec.command = command.toArray(new String[0]);
			}

			argSpec.setValue(exec);
		}
	}

}