How do I require one of the two Clap options?

Question

I am trying to write a CLI in Rust with the help of Clap. My command has 2 arguments, I want to make that just one or another can be specified, ex: command --command_a or command --command_b

#[derive(Debug, clap::Args)]
#[clap(name = "command")]
pub struct MyCommand {
    /// Argument1.
    #[clap(long, short)]
    command_a: String,
    /// Argument2.
    #[clap(long, short)]
    command_b: String,
    /// other optional events.
    #[clap(name = "others", long)]
    other_commands: Option<String>,
}

I can make both optional by adding command_a: Option<String>, and then in the code check that at least one has been provided, but can I do that using Clap?

Answer 1

You need to introduce an ArgGroup. To do that with the derive macros, create a struct Group and store it in MyCommand, and define it to be a group that is required but disallow multiple values:

#[derive(Debug, clap::Args)]
#[clap(name = "command")]
pub struct MyCommand {
    #[clap(flatten)]
    group: Group,
    #[clap(name = "others", long)]
    other_commands: Option<String>,
}

#[derive(Debug, clap::Args)]
#[group(required = true, multiple = false)]
pub struct Group {
    /// Argument1.
    #[clap(short, long)]
    command_a: Option<String>,
    /// Argument2.
    #[clap(short, long)]
    command_b: Option<String>,
}