PicocliCommands.invoke returns null not command result. Bug or feature?

[pford19]

• Version 4.7.6
• File: PicocliCommands.java
• Class: picocli.shell.jline3.PicocliCommands extends CommandRegistry

I started with the Picocli/Jline3 example to implement a shell.

invoke always returns null, and discards the command result. Is this a bug or feature? If a "feature" how best to signal a command loop to quit? (Other than end of file?)

My code, based on the example, looks like this

   // COMMAND LOOP
                while (true) {
                    try {
                        systemRegistry.cleanUp();
                        line = reader.readLine(prompt, rightPrompt, (MaskingCallback) null, null);
                        Object result = systemRegistry.execute(line);
                        // Oops, result is always null, this will not work
                        if (result instanceof Integer && ((Integer) result) < 0) {
                                // terminate loop
                                return;
                        }
                 } catch { 
                    ....
                 } 
                 
                 ...

// COMMAND                 

    @Command(name = "quit", mixinStandardHelpOptions = true)
    static class QuitCommand implements Callable<Integer> {
        public Integer call() {
            System.out.println("Bye now.");
            return -1; // signals termination of the command loop
        }
    }

PicocliCommands source in question:

    // For JLine >= 3.16.0
    @Override
    public Object invoke(CommandRegistry.CommandSession session, String command, Object... args) throws Exception {
        List<String> arguments = new ArrayList<>();
        arguments.add( command );
        arguments.addAll( Arrays.stream( args ).map( Object::toString ).collect( Collectors.toList() ) );
        cmd.execute( arguments.toArray( new String[0] ) ); // <<<<<<<<<<<<< execute result is discarded
        return null;  // <<<<<<<<<<<<< always returns null
    }

[remkop]

Good point.
I guess it's better to return cmd.getParseResult() instead of null.
What do you think?

[pford19]

Seems like the obvious choice. Completely new to picocli, so not immediately clear what the difference between the result of cmd.execute() vs. cmd.getParseResult(). But one or the other would make sense.

BTW, picocli is great. I had build a poor man's shell and command parser, and have been refactoring over the last week, with much delight.

[remkop]

Seems like the obvious choice. Completely new to picocli, so not immediately clear what the difference between the result of cmd.execute() vs. cmd.getParseResult(). But one or the other would make sense.

The cmd.execute() method returns an exit code, whereas
cmd.getParseResult returns an object with data built up by the parser. This is the richest information possible to return. Other values may be derived from the ParseResult. So it seems best to return ParseResult.

BTW, picocli is great. I had build a poor man's shell and command parser, and have been refactoring over the last week, with much delight.

Glad to hear it!