Nested subcommands?

[GoldsteinE]

hi! I’m trying to make an API like this:

myprog foo meow
myprog foo bark
myprog bar

a natural data type would be something like:

enum Foo {
    Meow,
    Bark,
}

enum Toplevel {
    Foo(Foo),
    Bar,
}

but I can’t figure out how to annotate it with bpaf attributes so that it works. #[bpaf(external)], recommended in nested parser docs doesn’t work on enum variants, and #[bpaf(command)] complains that “method meta is private” (and seemingly tries to treat Foo as a single positional argument). how to express an API with nested subcommands in bpaf?

[pacak]

You want something like this:

use bpaf::*;

#[derive(Debug, Copy, Clone, Bpaf)]
enum Foo {
    #[bpaf(command)]
    Meow,
    #[bpaf(command)]
    Bark,
}

#[derive(Debug, Copy, Clone, Bpaf)]
#[bpaf(options)]
enum Toplevel {
    #[bpaf(command)] // "foo" is a command, but its body is `external(foo)`
    Foo(#[bpaf(external(foo))] Foo),
    #[bpaf(command)]
    Bar,
}

fn main() {
    let r = toplevel().fallback_to_usage().run();
    match r {
        Toplevel::Foo(f) => match f {
            Foo::Meow => println!("Meow!"),
            Foo::Bark => println!("Bark"),
        },
        Toplevel::Bar => println!("bar!"),
    }
}

and #[bpaf(command)] complains that “method meta is private” (and seemingly tries to treat Foo as a single positional argument). how to express an API with nested subcommands in bpaf?

Can you share this example?

[GoldsteinE]

thanks for the response!

Can you share this example?

#[derive(Debug, Clone, Bpaf)]
#[bpaf(options)]
pub(crate) enum Foo {
    #[bpaf(command)]
    Meow,
}

#[derive(Debug, Clone, Bpaf)]
#[bpaf(options)]
pub(crate) enum Outer {
    #[bpaf(command)]
    Foo(Foo),
}

[pacak]

That's a fun one. .meta() is a trait method, but this trait is not implemented since it needs FromStr so instead rustc tries to call .meta() on the underlying struct which exists but private. I have to use macro to emulate lax monoidal functors and it simply glues code together. FWIW rustc also complains about missing FromStr...