Parsing multiple picocli (sub-)commands and a shell

Question

How do I build a Spring Boot 2.3 multi-command CLI application that can be run with single command, an @script, and interactively in picocli? It should behave like this:

manager -u <user> -p <pass> [list|create|delete] # run and exit
manager -u <user> -p <pass> @script              # run and exit
manager -u <user> -p <pass>                      # run shell

The username -u and password -p are required, and the three commands (list, create, and delete) each have different options and parameters.

Answer 1

The Spring Boot application is trivial:

@SpringBootApplication
public class Application {
    public static void main(String[] args) {
        System.exit(SpringApplication.exit(
            SpringApplication.run(Application.class, args))
        );
    }

}

And the Spring Boot CommandLineRunner with a return value is also simple and calls into picocli's CommandLine to parse and execute commands:

@Component
public class ApplicationRunner implements CommandLineRunner, ExitCodeGenerator {
    private int exitCode;

    @Override
    public void run(String... args) throws Exception {
        exitCode = new CommandLine(new ConnectCommand()).execute(args);
    }

    @Override
    public int getExitCode() {
        return exitCode;
    }

}

The ConnectCommand has showAtFileInUsageHelp = true which enables picocli's @-file support and mixinStandardHelpOptions which enable help and version information with "standard" options (-h, --help, etc.):

@Command(
    name = "manager",
    description = "The manager description",
    showAtFileInUsageHelp = true,
    mixinStandardHelpOptions = true,
    subcommands = {
        ListCommand.class,
        CreateCommand.class,
        DeleteCommand.class
    })
@Component 
public class ConnectCommand implements Runnable, ExitCodeGenerator {
    @Option(
        names        = {"-u", "--username"},
        description  = "The username")
    private String username;

    @Option(
        names        = {"-p", "--password"},
        description  = "The password")
    private String password;

    private int exitCode;

    @Override
    public void run() {
        // WIP: kick-off shell
    }

    @Override
    public int getExitCode() {
        return exitCode;
    }

}

And the (sub-)commands all take this form (sprinkle in picocli's @Option and @Parameters as necessary):

@Command(
    name = "list",
    mixinStandardHelpOptions = true,
    header = "list stuff")
@Component
class ListCommand implements Runnable{
    @Override
    public void run() {
        System.out.println("listing...");
    }

}

With this, the help now looks like:

Usage: manager [-hV] [-u=username] [-p=password] [@<filename>...] [COMMAND]
The manager description
      [@<filename>...]    One or more argument files containing options.
  -u, --username=name     The username
  -p, --password=pass     The password
  -h, --help              Show this help message and exit.
  -V, --version           Print version information and exit.
Commands:
  list    list stuff
  create  create stuff
  delete  delete stuff

And running a single command works:

java -jar manager.jar -u=myname -p=mypass list
listing...

And running an @-file containing 'list' also works:

java -jar manager.jar -u=myname -p=mypass @listing
listing...

Here's a sample repository. Now we need to fold-in the shell...