help_heading and clap_derive

[vorot93]

Is there any way to combine these two? It's probably the only blocker to OpenEthereum migrating from custom macros to Clap v3.

[pksunkara]

You can specify it for an arg field like this:

#[derive(Clap)]
struct B {
    #[clap(long, help_heading = "a")]
    time: bool
}

[vorot93]

Doesn't work.

#[derive(Clap, Debug)]
#[clap(
    setting = UnifiedHelpMessage,
    setting = DeriveDisplayOrder,
)]
struct B {
    #[clap(long, help_heading = Some("a"))]
    time: bool,
}

fn main() {
    let b = B::parse();
}

leads to the following output of cargo run -- --help

OPTIONS:
        --time       
    -h, --help       Prints help information
    -V, --version    Prints version information

[pksunkara]

Can you try help_heading(Some("a"))?

[vorot93]

Same result

[pksunkara]

Do you get any compilation errors? If yes, can you paste the cargo expand output?

[vorot93]

#![feature(prelude_import)]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std;
use clap::{AppSettings::*, Clap};
# [ clap ( setting = UnifiedHelpMessage , setting = DeriveDisplayOrder , ) ]
struct B {
    #[clap(long, help_heading(Some("a")))]
    time: bool,
}
impl ::clap::Clap for B {}
#[allow(dead_code, unreachable_code, unused_variables)]
#[allow(
    clippy::style,
    clippy::complexity,
    clippy::pedantic,
    clippy::restriction,
    clippy::perf,
    clippy::deprecated,
    clippy::nursery,
    clippy::cargo
)]
#[deny(clippy::correctness)]
impl ::clap::IntoApp for B {
    fn into_app<'b>() -> ::clap::App<'b> {
        Self::augment_clap(::clap::App::new("scratchpad"))
    }
    fn augment_clap<'b>(app: ::clap::App<'b>) -> ::clap::App<'b> {
        {
            let app = app.setting(UnifiedHelpMessage).setting(DeriveDisplayOrder);
            let app = app.arg(
                ::clap::Arg::new("time")
                    .long("time")
                    .help_heading(Some("a")),
            );
            app
        }
    }
}
#[allow(dead_code, unreachable_code, unused_variables)]
#[allow(
    clippy::style,
    clippy::complexity,
    clippy::pedantic,
    clippy::restriction,
    clippy::perf,
    clippy::deprecated,
    clippy::nursery,
    clippy::cargo
)]
#[deny(clippy::correctness)]
impl ::clap::FromArgMatches for B {
    fn from_arg_matches(matches: &::clap::ArgMatches) -> Self {
        B {
            time: matches.is_present("time"),
        }
    }
}
#[automatically_derived]
#[allow(unused_qualifications)]
impl ::core::fmt::Debug for B {
    fn fmt(&self, f: &mut ::core::fmt::Formatter) -> ::core::fmt::Result {
        match *self {
            B {
                time: ref __self_0_0,
            } => {
                let mut debug_trait_builder = f.debug_struct("B");
                let _ = debug_trait_builder.field("time", &&(*__self_0_0));
                debug_trait_builder.finish()
            }
        }
    }
}
fn main() {
    let b = B::parse();
}

[CreepySkeleton]

This is a bug in clap itself, not derive:

use clap::{App, Arg};

fn main() {
    App::new("app")
        .arg(Arg::from("--time").help_heading(Some("a")))
        .get_matches_from(&["test", "--help"]);
}

app 

USAGE:
    test [FLAGS]

FLAGS:
    -h, --help       Prints help information
        --time       
    -V, --version    Prints version information

I took liberty to report it as #1955