Question: how to extract {flags, opts, subcommands, ...}

[yoshuawuyts]

Heya 👋,

I was wondering what the recommended approach is to extract the currently used flags, subcommands, opts (and similar).

My goal is to generate man pages from a Clap struct, with the short versions and descriptions included. I've tried app.write_long_help(), but having to parse strings using regexes seems a bit wasteful.

I've also been digging into Clap's (undocumented) internals but given it's all undocumented, I take it that it might not have any stability guarantees.

Current Best Approach I've Found

#[macro_use]
extern crate structopt;

use structopt::StructOpt;

mod cli;

fn main() {
  let mut app = cli::Opts::clap();
  let mut stdout = std::io::stdout();
  app.write_long_help(&mut stdout).unwrap();   // We need to run this first.
  for f in app.p.flags() {
    println!("flag {:?}", &f);                 // Otherwise this doesn't work.
  }
}

So umm, to make these questions a bit more concrete:

Concrete Questions

• What's going on in app.write_long_help that provisions app.p.flags() with its contents?
• Is there a better way to extract flags than what we're currently doing?
• If there currently isn't a better way, could we perhaps add an interface to access this information?

---

I hope these questions make sense. Thanks so much for your time! ✨

[kbknapp]

This is actually a goal of 3.x! So if you'd like to work on this problem set on the v3-master branch it would be HIGHLY appreciated!

The v3-master branch is quite different from the current master branch (i.e. v2) in that you iterate the subcommands and args directly and not through a Parser facade.

In the v3-master branch you'd use macros (flags!, opts!, subcommands!, positionals! etc.) which have already been defined.

[yoshuawuyts]

Oh, this is amazing! - I'll dig further into the v3 branch then. Thanks for taking your time to reply! ✨

[pksunkara]

Should be fixed by #1736. cc @CreepySkeleton

[CreepySkeleton]

Yeah, right. Will get to it 11, should be done in a couple of days from then.