Allow mixins to get a reference to the command they are mixed into

[remkop]

Allow mixins to get a reference to the command they are injected into.

Currently, having a @Spec-annotated field in a Mixin will result in the CommandSpec of the mixin being injected instead of the CommandSpec of the target command (where the mixin is mixed into).

This makes it impossible to climb the command hierarchy in a generic way in a mixin.

A possible solution is something like this:

public @interface Spec {
    enum Target { SELF, MIXEE}

    Target value() default Target.SELF;
}

This would allow for usage like this:

static class VerbosityMixin {
    @Spec CommandSpec mySpec; // spec of the VerbosityMixin itself (not useful)

    @Spec(Spec.Target.MIXEE)
    CommandSpec mixeeSpec; // spec of the command where the @Mixin is used

    /**
     * Delegates the specified verbosity to the top-level (root) command.
     * @param verbosity the new verbosity value
     */
    @Option(names = {"-v", "--verbose"})
    public void setVerbose(boolean[] verbosity) {
        CommandSpec root = mixeeSpec.root(); // #960

        MyApp myApp = root.commandLine().getCommand();
        myApp.verbosity = verbosity;
    }
}

(I created a separate ticket, #960, for getting the root (top-level) command from a command spec.)

Update: a full-blown example is here.

[remkop]

This is now implemented and documented in master.
Closing this ticket.