[SOLVED] Is there any straightforward way for Clap to display help when no command is provided?

Is there any straightforward way for Clap to display help when no command is provided?

I'm using the Clap crate for parsing command line parameters. I've defined a subcommand ls that should list files. Clap also defines a help subcommand that displays information about the application and its usage.

If no command is provided, nothing gets displayed at all, but I want the app to display help in that case.

I've tried this code, which looks pretty straightforward, but it doesn't work:

extern crate clap;

use clap::{App, SubCommand};

fn main() {
    let mut app = App::new("myapp")
        .version("0.0.1")
        .about("My first CLI APP")
        .subcommand(SubCommand::with_name("ls").about("List anything"));
    let matches = app.get_matches();

    if let Some(cmd) = matches.subcommand_name() {
        match cmd {
            "ls" => println!("List something here"),
            _ => eprintln!("unknown command"),
        }
    } else {
        app.print_long_help();
    }
}

I get an error that app is used after move:

error[E0382]: use of moved value: `app`
  --> src/main.rs:18:9
   |
10 |     let matches = app.get_matches();
   |                   --- value moved here
...
18 |         app.print_long_help();
   |         ^^^ value used here after move
   |
   = note: move occurs because `app` has type `clap::App<'_, '_>`, which does not implement the `Copy` trait

Reading through the documentation of Clap, I've found that the clap::ArgMatches that's returned in get_matches() has a method usage that returns the string for usage part, but, unfortunately, only this part and nothing else.

Solution