Parse a Vec<T> out of a single comma-delimited argument without consuming the rest

[stijndcl]

I'm working on a CLI interface that takes multiple consecutive parameters that are comma-delimited lists. These are consecutive positional arguments, followed by some other positional arguments.

Example usage: ./tool a,b,c 1,2,3 /out.

This is the current setup I'm using:

#[derive(Parser, Debug)]
struct Cli {
    #[clap(num_args = 1.., value_delimiter = ',')]
    first: Vec<String>,
    #[clap(num_args = 1.., value_delimiter = ',')]
    second: Vec<u64>,
    third: PathBuf,
}

Usually spaces are used to delimit values in vectors, so it is ambiguous which value belongs to which vector. As a result, first swallows everything and second and third throw an error saying the value is missing.

In my case, I want spaces to denote the end of an argument - solely relying on the commas to delimit items in a list. I hoped value_delimiter = ',' would do this for me but it does not - values separated by commas are grouped together correctly, but the remaining arguments are still swallowed.

I also tried using value_terminator = ' ' to force it to stop looking after hitting a space, but that did nothing either.

Is there a way to get the behaviour I want without enforcing --long argument usage (keeping it positional as in the example above)?

I could use String as the type and parse it into a Vec<String> afterwards using split(), but I'd like for Clap to handle this for me instead if possible. Also, using a Vec over a String makes the help formatter show explicitly that an argument will take multiple values, which is a feature I don't want to lose out on.

[epage]

Set num_args = 1. num_args is how many raw arguments you want to consume, rather than validation on how many values you did consumed.

[stijndcl]

Nope, using num_args = 1 with my above input gives this error:

error: the following required arguments were not provided:
  <SECOND>...
  <THIRD>

indicating that everything was consumed into the first argument. Commenting out the other fields and printing first confirms this as well:

fn main() {
    let args = Cli::parse();
    println!("{:?}", args.first);
}

#[derive(Parser, Debug)]
struct Cli {
    #[clap(num_args = 1, value_delimiter = ',')]
    first: Vec<String>,
    // ... here be commented out second and third arg
}

Output:

$ ./tool a,b,c 1,2,3 /out
["a", "b", "c", "1", "2", "3", "/out"] # Expected output for the first argument is just ["a", "b", "c"].

[epage]

Check out the arg types referencehttps://docs.rs/clap/latest/clap/_derive/index.html#arg-types). You'll need to undo what it does. In particular, you also need to set ArgAction::Set.

#4626 is the issue trying to figure out a way to improve this.