Flags from structures

[saschagrunert]

I’m quite not sure if this is nicely doable with golang, because we have nothing like a procedural macro for it. It could be done with reflection and tags…

Anyways, here comes the idea: I saw in the upcoming release of clap (a command line parser for Rust) that it is capable of deriving the flags from a structure, like this:

#[derive(Clap)]
#[clap(
    after_help = "More info at: https://github.com/saschagrunert/kubernix",
    author = "Sascha Grunert <[email protected]>",
    raw(global_setting = "AppSettings::ColoredHelp"),
    raw(version = "crate_version!()")
)]
/// The global configuration
pub struct Config {
    #[get = "pub"]
    #[clap(subcommand)]
    /// All available subcommands
    subcommand: Option<SubCommand>,

    #[get = "pub"]
    #[clap(
        default_value = "kubernix-run",
        env = "KUBERNIX_RUN",
        global = true,
        long = "root",
        short = "r",
        value_name = "PATH"
    )]
    /// Path where all the runtime data is stored
    root: PathBuf,

    …
}

The amazing thing is now that I’m able to use a single configuration structure and map it directly to command line arguments. So there is no need of an additional structure any more. The documentation comments (starting with ///) are automatically transferred into the help message as well.

I would like to spin up the discussion if we are considering something like this for this library, too. What do you think?

[asahasrabuddhe]

These guys are doing what you are talking about @saschagrunert

https://github.com/alecthomas/kong

[saschagrunert]

Ah okay we could add something via go tags. I think this might be a nice feature.

[Southclaws]

I've also done struct tags -> cli.App via reflection. Feel free to pull in, I could make a PR for this repo if that's of interest http://github.com/Southclaws/clive

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[stale[bot]]

Closing this as it has become stale.

[refs]

This would actually be a very thoughtful addition, has it been considered at all?

[dearchap]

The way I see it urfave/cli gives you the basic building blocks. User could use reflection and tags and build the necessary flag slice for commands. I like this feature but I'd rather not have the cli library do it directly