Ignoring unexpected arguments

[frabert]

Is there a way to instruct clap to ignore unexpected arguments? Let's say I'm only interested in -I arguments, and ignore everything else. Right now, with something like this:

#[derive(Parser, Debug)]
#[clap()]
struct MyArgs {
    #[clap(short = 'I')]
    important_arg: Vec<String>,
}

the program will error out if I pass it e.g. -Ifoo -I correct --not correct. Is it possible to override this behavior?

[epage]

For now we have https://docs.rs/clap/latest/clap/struct.App.html#method.ignore_errors

Longer term we also want #1404

[frabert]

Very nice, thank you! I take it there's no way to obtain the same with the Derive API?

[epage]

Its available; the derive API just maps attributes to builder functions. See https://github.com/clap-rs/clap/blob/master/examples/derive_ref/README.md

[chensk]

all these pages are invalid, please update it

[eranfu]

My way:

lazy_static! {
    pub static ref ARGS: Args =
        Args::from_arg_matches_mut(&mut Args::command().ignore_errors(true).get_matches(),)
            .unwrap();
}

#[derive(Parser, Debug)]
pub struct Args {
    #[command(subcommand)]
    pub sub_command: Option<SubCommand>,
}

Note:
There is .ignore_errors(true)

[eranfu]

BTW. I think there should be a method named ignore_unknown_args().
Then, other errors will not be ignored.

[epage]

Oh, I just didn't know that the attribute can modify the Command directly. Thanks~

In the derive reference, this falls under the "raw attributes" which means any builder method can be used as an attribute. #4090 is for exploring how to make this more discoverable

BTW. I think there should be a method named ignore_unknown_args().
Then, other errors will not be ignored.

#1404 is the issue for that

[eranfu]

Looks good to me. Thanks!

[boozook]

With ignore_errors all help triggers (-h, --help) are broken because they throws as an error.

[epage]

#4392 was the issue for that which was resolved in #4392 and released in 4.3.9

[asharkhan3101]

If you want to ignore errors in derive API.

#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None, ignore_errors(true))]
struct Cli {
    /// Include paths for proto files
    #[arg(short, long, value_delimiter = ',')]
    include_paths: Option<Vec<String>>,
}