Yet another discussion about completions

[SergioRibera]

Yep, this is another discussion about the topic, but in this case with the intention of making a PR soon, more than everything I come to debate a little the functionality that I would like to implement, reading about all the issues and related discussions, I have come to the conclusion of adding in the ValueHint a parameter, something like ValueHint: :ValuesFromCommand(String) which when processed would embed that String in the autocomplete file that is generated, I do not know if I let myself explain, this contribution would be valid for the next version of clap?

[epage]

At the moment, ValueHint is Copy, so we can't carry a String payload.

It isn't quite clear what String is and how it would interact with things.

I'm not finding an issue for it but my one idea is that as we explore adding a plugin system into clap where arbitrary data can be attache to a Command or an Arg ((#3476)), clap_complete will provide BashScript, ZshScript, etc that would allow you to attach to an Arg to inject arbitrary code into the completion script.

We are also working on #3166 which will allow clap_complete to provide a ValueCompleter plugin where the developer will be able to write rust code to customize completions for an Arg.

[SergioRibera]

Mmm, definitely your idea is much more concrete and extensive for developers, I was thinking of something simpler to implement that would allow a prompt output to be implemented in different projects while you finish adding more complete features, my idea was more oriented to be able to use it with any type of command, something like this

#[derive(Subcommand, Clone, Debug)]
pub enum PackageExample {
    Remove {
        // ...
        #[clap(value_hint = ValueHint::ValuesFromCommand("{binary_name} list --installed --raw"))]
        package_name: &str,
    },
}

or

#[derive(Subcommand, Clone, Debug)]
pub enum PackageExample {
    Remove {
        // ...
        #[clap(value_hint = ValueHint::ValuesFromCommand("binary list --raw | grep -e \"installed\" | cut -d\" \" -f1"))]
        package_name: &str,
    },
}

I know that maybe there are problems like some commands not available, but I believe that it is a simple way to implement it, I do not know what you say, the same with the subject of the name of the binary, maybe it is good that in the String it can be replaced by the actual name of the binary

[Atreyagaurav]

Any progress on this? I've been manually editing the generated file and adding my commands, but it's become tedious to do every time i add some flags and subcommands.

[epage]

As I mentioned, ValueHint itself is a dead-end because the type is Copy and changing that would require a breaking change.

Command now supports plugins, internally. We have not settled on the public API yet. We need to settle on that API and extend it to Arg before clap_complete can add anything like this.

I will say

• completions are not my current focus area and so do not expect any work on this unless its coming from the community
• I would highly recommend that community effort focus on the native completion engine as I view the static completions as a dead end and major work done on them to be throwaway,.
• However, I might be open to reviewing work done on it once we get the plugin system ready
• One way to unblock the plugin system is to hide it behind unstable-plugin so we don't have to worry about getting it right the first time and can use work like this to get feedback on how to improve it.