Argument or group 'value' specified in 'conflicts_with*' for 'a' does not exist

1

I'm trying to define arguments in a Rust program using the clap crate. I want to achieve the following behavior:

  • Users can either provide individual coefficients (a , b , and c ) for a quadratic equation or a single argument containing the entire mathematical expression.
  • I've tried using conflicts_with on the individual coefficient arguments to prevent them from being used with the argument for the entire expression). However, I encounter an error about a missing argument (value ) when referencing it in conflicts_with .

Code Snippet:


#[derive(Parser)]
#[command(author, version, about, long_about = None)]
pub struct Command {
    #[clap(subcommand)]
    pub argument : Arguments,
    ///...
}


#[derive(Subcommand)]
pub enum Arguments {
    Playground,
    /// ...
     #[clap(about = "Handle quadratic equations")]
    Quadratic {
        #[clap(subcommand)]
        subcommand: QuadraticsCommands,

        #[command(flatten)]
        input : QuadraticInput
    },
}

#[derive(Subcommand)]
pub enum QuadraticsCommands { 
    Filler
}

#[derive(Args,Debug,Clone)]
#[clap(group = clap::ArgGroup::new(QUAD_GROUP))]
pub struct QuadraticInput { 
    #[clap(
        short='v',
        long="value",            
        help = "The mathematical expression or equation to evaluate (required).",    
        group = QUAD_GROUP,
        conflicts_with_all = ["a","b","c"]
    )]
    equation_or_expresion : String,

    /// Provide the coefficient 'a' of the quadratic equation.
    #[clap(
        short,
        group = QUAD_GROUP,
        conflicts_with = "value",
        help = "Provide the coefficient 'a' of the quadratic equation."
    )]
    a: String,

    /// Provide the coefficient 'b' of the quadratic equation.
    #[clap( 
        short,
        group = QUAD_GROUP,
        conflicts_with = "value",
        help = "Provide the coefficient 'b' of the quadratic equation."
    )]
    b: String,

    /// Provide the coefficient 'c' of the quadratic equation.
    #[clap( 
        short,
        group = QUAD_GROUP,
        conflicts_with = "value",
        help = "Provide the coefficient 'c' of the quadratic equation."
    )]
    c: String,
}

Now while running the following command , or any command I get this error

cargo run -- --playground

The error

thread 'main' panicked at /root/.cargo/registry/src/index.crates.io-6f17d22bba15001f/clap_builder-4.5.8/src/builder/debug_asserts.rs:214:13:
Command quadratic: Argument or group 'value' specified in 'conflicts_with*' for 'a' does not exist
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

How can I achieve the desired behavior using conflicts_with or other clap features?

Additional Notes:

2

I'm not sure if this is the best way to do it, but in the past I've used multiple(false) in an ArgGroup to only allow one of two args to be selected.

For example, to implement all_in_one XOR (a AND b AND c), you can try something like this:

use clap::ArgGroup;
use clap::Parser;

#[derive(Parser)]
#[clap(group(
    ArgGroup::new("quadratic")
        .required(true)
        .multiple(false)
        .args(&["all_in_one", "a"])
))]

pub struct QuadraticInput {
    // Argument a
    #[clap(long, requires_all = ["b", "c"])]
    pub a: Option<String>,

    // Argument b
    #[clap(long, requires_all = ["a", "c"])]
    pub b: Option<String>,

    // Argument c
    #[clap(long, requires_all = ["a", "b"])]
    pub c: Option<String>,

    /// Everything in one
    #[clap(long)]
    pub all_in_one: Option<String>,
}

fn main() {
    let args = QuadraticInput::parse();

    println!("all_in_one {:#?}!", args.all_in_one);
    println!("a {:#?}!", args.a);
    println!("b {:#?}!", args.b);
    println!("c {:#?}!", args.c);
}
3

Thank you

4

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