[Question] positional argument with at least one value mandatory

[Geobert]

Is there a way to specify that a positional arg need at least one value?

#[derive(FromArgs)]
/// MyCMD
struct Opt {
    #[argh(positional)]
    /// script files to run
    test_file: Vec<PathBuf>,
}

gives me:

Usage: mycmd.exe [<test_file...>]

Which suggests the tool can work without any input when it needs at least one.

[benbrittain]

There is not currently, I'd potentially be open to a PR depending on how it's implemented.

I'd suggest checking after parsing if it meets the conditions for now.

[Geobert]

Proposal

#[derive(FromArgs)]
/// MyCMD
struct Opt {
    #[argh(positional(1))] // expected number of items
    /// script files to run
    test_file: Vec<PathBuf>,
}

if minimum number of expected item > 0, do not print brackets.

I'm not very familiar with proc_macro yet, so I don't know if this is acceptable :)

EDIT: I'm checking after parsing for now, yes :)

EDIT2: even better? if not Option<_>, it is mandatory, regardless of the field kind

[trevarj]

I started hacking this type of syntax into the attribute macro, but it seems that the requested functionality is unclear.

Should inside the parenthesis be the exact expected number of values or the minimum number number of values expected?

I'm able to get the macro syntax to play nice, i.e positional(1) or falling back to just positional, but after that it gets way over my head. Time to learn!

[Geobert]

Good question, my first post speaks about "at least" and the 2nd post is "expected number of items". Is it possible to specify something like: =1 or >=1 or >1 for "exact number", minimum number, more than number?

[trevarj]

I didn't see that ability in my exploration. I only saw meta data capabilities for key value pairs which would allow positional=1 or a list type that would allow positional(1).

Ben Brittain or another maintainer would know much better than me.