kbknapp / clap-rs / 1869

94%

Pull #465

travis-ci

feat(Macros): adds a subcommands! macro for defining an enum to access subcommands

Instead of defining all trait implementations manually, one can now do
the following:

```
// Note lowercase variants, the subcommand will be exactly as typed here
subcommands!{
    enum MyProg {
        show,
        delete,
        do,
    }
}

// Alternatively, if you wish to have variants which display
// differently, or contain hyphens ("-") one can use this variation of
// the macro
subcommands!{
    enum MyProgAlt {
        Show => "show",
        Delete => "delete",
        DoStuff => "do-stuff",
    }
}

fn main() {
    let m = App::new("myprog")
        .subcommand(SubCommand::with_name(MyProg::show))
        .subcommand(SubCommand::with_name(MyProg::delete))
        .subcommand(SubCommand::with_name(MyProg::do))
        .get_matches();

    match m.subcommand() {
        (MyProg::show, _) => println!("'myprog show' was used"),
        (MyProg::delete, _) => println!("'myprog delete' was used"),
        (MyProg::do, _) => println!("'myprog do' was used"),
        (MyProg::None, _) => println!("No subcommand was used"),
    }
}
```

**NOTE:** It's good practice to make the name of the enum the same as
the parent command, and the variants the names of the actual subcommands

Notice a fourth "None" option was automatically added.

This allows rustc to do some checking for you, i.e. if you add another
subcommand later, but forget to check for it, rustc will complain about
NonExaustive matches. Likewise, if you make a simple spelling or typing
error.

Relates to #459

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