write_long_help is wonky on get_subcommands_mut values

[Gankra]

Please complete the following tasks

• I have searched the discussions
• I have searched the open and rejected issues

Rust Version

rustc 1.61.0-nightly (458262b13 2022-03-09)

Clap Version

3.1.8

Minimal reproducible code

The main thing is just:

    // Cli is derive(Parser)
    let mut full_command = Cli::command();
    let mut todo = vec![&mut full_command];

    while let Some(command) = todo.pop() {
        // Get the long help for this (sub)command
        let mut help_buf = Vec::new();
        command.write_long_help(&mut help_buf).unwrap();

        // print help_buf...

        // Add subcommands to working queue
        todo.extend(command.get_subcommands_mut());
    }

But the "complete" program is all of this:

use std::{io::Write, error::Error};

use clap::{CommandFactory, Parser, Subcommand};

#[derive(Parser)]
#[clap(version, about, long_about = None)]
#[clap(propagate_version = true)]
struct Cli {
    // Subcommands
    #[clap(subcommand)]
    command: Option<Commands>,

    // Some random flags 
    #[clap(long)]
    locked: bool,
    #[clap(long)]
    log_file: Option<String>,
}

#[derive(Subcommand)]
enum Commands {
    /// initialize buggyhelp for your project
    #[clap(disable_version_flag = true)]
    Init(InitArgs),

    /// Fetch the source of `$crate $version`
    #[clap(disable_version_flag = true)]
    Fetch(FetchArgs),

    /// Print --help as markdown (for generating docs)
    #[clap(disable_version_flag = true)]
    #[clap(hide = true)]
    HelpMarkdown(HelpMarkdownArgs),
}

#[derive(clap::Args)]
struct InitArgs {}

#[derive(clap::Args)]
struct FetchArgs {
    krate: String,
    version: String,
}

#[derive(clap::Args)]
struct HelpMarkdownArgs {}


fn main() -> Result<(), Box<dyn Error>>  {
    let cli = Cli::parse();

    match &cli.command {
        Some(Commands::HelpMarkdown(..)) => cmd_help_markdown()?,
        _ => unimplemented!(),
    }

    Ok(())
}

fn cmd_help_markdown() -> Result<(), Box<dyn Error>> {
    let mut full_command = Cli::command();
    let mut todo = vec![&mut full_command];

    while let Some(command) = todo.pop() {
        let mut help_buf = Vec::new();

        command.write_long_help(&mut help_buf).unwrap();
        let help = String::from_utf8(help_buf).unwrap();
        println!("{}", help);

        todo.extend(command.get_subcommands_mut());
    }

    Ok(())
}

Steps to reproduce the bug with the above code

cargo run -- help-markdown

Actual Behaviour

The long_help outputs for the subcommands are weirdly different from myapp subcommand --help:

• USAGE is subcommand ... instead of myapp subcommand ...
• ARGS have weird amounts of padding

fetch 0.1.0
Fetch the source of `$crate $version`

USAGE:
    fetch <KRATE> <VERSION>

ARGS:
    <KRATE>


    <VERSION>


OPTIONS:
    -h, --help
            Print help information

Expected Behaviour

It's not obvious why this would produce substantially different output from the "normal" way to get --help on the CLI.

Additional Context

The reason I am doing these crimes is that I have a secret command that mangles the --help output into a usable markdown form to add to the end of a README.md: https://gist.github.com/Gankra/349dcf6732262ed33b2aa216243a75be

Debug Output

No response

[epage]

This is most likely due to an under-developed part of clap. To work around it, you should call full_command._build_all(); before doing anything else.

#2911 is the issue for improving this.

[epage]

Without any activity on this, I'm assuming the solution provided is sufficient. If not, let us know and we can re-open!

[Gankra]

oh yes sorry, I patched around the issue by just "expecting" the wonky output, I haven't had a chance to look at _build_all() (leading underscore has me suspicious that this is no better than me hacking around it...).

[epage]

I've released v3.1.10 with Command::build so people don't have to feel bad for using it until we've replaced it.