Improve docs for interactive options (was:Input on interactive flag not working on Windows cmd)

[smalirizvi]

Input is not being taken in on interactive flag set to true when entering input on windows cmd.

[remkop]

Are you using jline2?
Is this issue perhaps similar to this one: #767

[remkop]

@smalirizvi, are you using JLine 2?

If so, there is a workaround: use a custom parameter consumer that uses the JLine 2 API to read a password interactively from the console.

The picocli-shell-jline2 README has an example: see the InteractiveParameterConsumer class in the README.

[remkop]

@smalirizvi Can you provide more information on how to reproduce this issue?

[remkop]

I am going to assume that you expected picocli to prompt the user for input when the interactive option is not specified when the program is invoked.
Instead, picocli only prompts the user when the interactive option is specified without parameter:

$ myprogram                             # option not specified: no prompting
You provided value 'null'

$ myprogram --interactive-option=abc    # option specified with parameter: no prompting
You provided value 'abc'

$ myprogram --interactive-option        # option specified WITHOUT parameter: prompt for input
Enter value for --interactive-option (...):    #  <--- type xxx and hit Enter
You provided value 'xxx'

Applications that also need the user to be prompted when the option is not specified, need to do this in the business logic.
For example:

@Command
public class Main implements Runnable {
    @Option(names = "--interactive", interactive = true)
    String value;

    public void run() {
        if (value == null) {
            // alternatively, use Console::readPassword
            value = System.console().readLine("Enter value for --interactive: ");
        }
        System.out.println("You provided value '" + value + "'");
    }

    public static void main(String[] args) {
        new CommandLine(new Main()).execute(args);
    }
}

I believe this question has come up before, so I will add this example to the user manual.