imp(errors): Provide the missing required arguments as info

[nickelc]

Collect the missing required arguments for Error::info.

Code

use clap::clap_app;

fn main() {
    let app = clap_app!(prog =>
        (@arg arg1: +required)
        (@arg arg2: -o +required)
    );
    let m = app.try_get_matches();
    dbg!(m);
}

cargo r Output

[src/prog.rs:9] m = Err(
    Error {
        cause: "The following required arguments were not provided:\n    <arg1>\n    -o",
        message: error: The following required arguments were not provided:
            <arg1>
            -o
        
        USAGE:
            prog [FLAGS] <arg1> -o
        
        For more information try --help
        ,
        kind: MissingRequiredArgument,
        info: Some(
            [
                "<arg1>",
                "-o",
            ],
        ),
    },
)

[CreepySkeleton]

Why do you need them?

[nickelc]

Other error kinds provide info of wrong arguments, conflicts etc. MissingRequiredArgument is missing such info.

I want to use clap as command parser for a discord bot and I'll eventually generate the help & error messages

[CreepySkeleton]

I asked because I want to remove the field entirely because I find it useless. For example, if you want to render the message, you can just err.to_string().

[pksunkara]

It's not useless. We are providing some programmable information in that field as @nickelc said.

[pksunkara]

@CreepySkeleton I gave the reasons in #1976. Let's go ahead and merge this one.

[CreepySkeleton]

hey @nickelc , could you please explain why exactly you need the names of the args? Why doesn't to_string suit you? We're having a dispute around this field, and your input would allow for more weighted decision.

[pksunkara]

The error messages he wants to write is probably not the ones we are generating. And since .to_string() needs to be parsed to generate his custom message, he would much prefer and field in the error with the necessary related info.

[nickelc]

I want to parse discord messages with clap but generate the help & error messages be myself as discord messages.

Maybe some kind of help & error renderer trait could help here to make clap more customizable.

[CreepySkeleton]

I'm now convinced this can be useful, albeit seldom.

Maybe some kind of help & error renderer trait could help here to make clap more customizable.

If you have a solid idea, open a separate issue.

bors r+

[bors]

Build succeeded:

• CI
• continuous-integration/travis-ci/push
• clap-rs.clap