Is it possible to use ValueParser to parse Vec<String>

[budde25]

I want to do some custom parsing/validation on a Vec with num_args = 1.. but I can't figure out a way parse it with value_parser.

Cli is that basic approach that works fine, but when i replace it with a custom type it doesn't allow parsing from a Vec

I also tried implementing FromStr for ValidCommand but in that case it drops all the args after the first one.

Thanks!

use std::str::FromStr;

use clap::{Parser, ValueHint, value_parser};

#[derive(Debug, Parser)]
pub struct Cli {
    #[clap(value_hint = ValueHint::CommandWithArguments, num_args = 1.., trailing_var_arg = true, required = true)]
    command: Vec<String>,
}

#[derive(Debug, Parser)]
pub struct Cli2 {
    #[clap(value_hint = ValueHint::CommandWithArguments, num_args = 1..,  trailing_var_arg = true, required = true, value_parser = value_parser!(ValidCommand))]
    command: ValidCommand,
}

#[derive(Debug, Clone)]
struct ValidCommand(Vec<String>);

// doesn't do anything
impl TryFrom<Vec<String>> for ValidCommand {
    type Error = String;

    fn try_from(value: Vec<String>) -> Result<Self, Self::Error> {
        for v in &value {
            if !v.is_ascii() {
                return Err(String::new());
            }
        }
        Ok(Self(value))
    }
}

fn main() {
    println!("Hello, world!");

    let args = ["bin", "arg1", "arg2", "arg3"];

    let cmd = Cli::try_parse_from(args).expect("valid command");
    assert_eq!(cmd.command, args[1..]);

    let args = ["bin", "arg1", "arg2", "arg3"];

    let cmd = Cli2::try_parse_from(args).expect("valid command");
    assert_eq!(cmd.command.0, args[1..]);
}

[epage]

value_parser takes a single value and outputs whatever value you want, including a series of values. It does not operate on a series of values. That would need to be handled by custom validation logic. Right now that must be done after parsing in application code. We are considering what ways to allow users to extend validation.