shell competion for sub-commands using derive OM

[ProphetLamb]

Given a derive based CLI like so

#[derive(Parser, Debug)]
#[clap(author, version, about, long_about = None)]
struct Args {
    #[clap(subcommand)]
    command: Cmd,
}

#[derive(Subcommand, Debug)]
enum Cmd {
    /// Initializes a directory as a backclone repository.
    Init(InitCtx),
    /// Adds to the repository.
    Add(AddCtx),
    /// Validates links to the repository of select definitions.
    Check(DeployCtx),
    /// Deploys links to the repository according to select definitions in the manifest.
    Deploy(DeployCtx),
    /// Validates a template expression and enumerates possible results.
    Verify(VerCtx),
}

#[derive(Parser, Debug)]
struct InitCtx {
    /// Path to the directory to initialize as a repository
    #[clap(default_value = "./", value_hint = ValueHint::DirPath)]
    repository_path: PathBuf,
}

[...]

fn main() {
    let res = match Args::parse().command {
        Cmd::Init(ctx) => init(ctx),
        Cmd::Add(ctx) => add(ctx),
        Cmd::Check(ctx) => check(ctx),
        Cmd::Deploy(ctx) => deploy(ctx),
        Cmd::Verify(ctx) => verify(ctx),
    };
    if let Err(e) = res {
        println!("{}", e);
    }
}

I which to enable autocompletion for sub-commands using clap_complete. How do I go about it?

The docs explain how I may enable shell completion given a Command struct, but such a struct only exists when using the builder syntax. If I were to use the builder syntax, I would have to parse the entire command to the same OM, so I would basically write duplicate, ugly, imperative code. So if at all possible, I would like to avoid the builder syntax and stick with the derive syntax.

[epage]

The docs explain how I may enable shell completion given a Command struct, but such a struct only exists when using the builder syntax.

Derive Reference's tips calls attention to how to access a Command:

To get access to a Command call CommandFactory::command (implemented when deriving Parser)

This is important for other reasons, like

Proactively check for bad Command configurations by calling Command::debug_assert in a test (example)

clap_complete also comes with a derive example, https://github.com/clap-rs/clap/blob/master/clap_complete/examples/value_hints_derive.rs.

[ProphetLamb]

Oh, I missed that. Thanks a lot for pointing me in the right direction.
Cheers!

[andreasnuesslein]

updated example url: https://github.com/clap-rs/clap/blob/master/clap_complete/examples/completion-derive.rs