optionalValue

Allow this option to be specified with or without an explicit value.

If the option is specified on the command line without a value, default will be used.

To avoid ambiguity when combined with arguments, you can set acceptsUnattachedValue to false to require that the option's value be specified like --foo=bar rather than --foo bar.

You can use optionalValueLazy if you need to reference other parameters.

Example

val log by option().optionalValue("verbose").default("none")

> ./tool --log=debug
log level == debug

> ./tool --log
log level == verbose

> ./tool
log level == none