Ability to set min_values per occurance when multiple_occurances is used

[tmccombs]

Please complete the following tasks

• I have searched the discussions
• I have searched the open and rejected issues

Clap Version

3.1.5

Describe your use case

I have an option that supports multiple occurrences, but each occurrence is independent, and needs a minimum of 1 value passed to it. I'm using grouped_values_of to get the groups of values. If I use .min_values(1), then it requires that there is at least one value in total, not that there is one value per occurance.

Here's some example code:

use clap::*; // 3.1.5

fn main() {
 let app = Command::new("test")
 .arg(Arg::new("example").short('x').min_values(1).multiple_occurrences(true).value_name("x"));
 let matches = app.get_matches_from(&["test", "-x", "a", "-x"]);
 println!("{:?}", matches);

}

This produces a successful match, but I want it to fail, because no argument is given to the second occurance of -x.

Describe the solution you'd like

Ideally, .min_values would behave as I've described. And if the current behavior is unintentional , then this is probably a bug, and it might be worth changing. However, changing min_values's behavior would technically be backwards incompatible, so it may be necessary to introduce a new api like min_values_per_occurance (and probably a similar max_values_per_occurance).

Alternatives, if applicable

The only alternative I know of is to have the application check that enough arguments are provided to each group returned by grouped_values_of rather than letting clap do the validation for me.

Additional Context

See sharkdp/fd#960 (comment).

[tmccombs]

See also the workaround in sharkdp/fd@eb65a7e

[epage]

Thanks for reporting this!

I had thought we had an issue for this (because I was aware of this and agree that this should change).

However, I worry about people relying on this and we'd need to wait until 4.0, though we might be able to do it earlier as part of the unstable-v4 feature flag.

[epage]

Missed this, its resolved via #2688. The new num_args is per occurrence.