Flag implies other flags

[camsteffen]

Make sure you completed the following tasks

• Searched the discussions
• Searched the closed issues

Describe your use case

I have an application that generates a bunch of files depending on several flags. I want to have a "save-all" flag that implies all of the more granular "save-x" flags. I'm surprised that I can't find any similar request through searching.

Here is an example: (simplified for this post)

App::new("MyApp")
    .arg(Arg::with_name("save_all")
        .long("save-all")
// *** this is what I want to do *** //
        .implies_all(&["save_image", "save_stats", "save_text"]))
    .arg(Arg::with_name("save_image")
        .long("save-image"))
    .arg(Arg::with_name("save_stats")
        .long("save-stats"))
    .arg(Arg::with_name("save_text")
        .long("save-text"))

Describe the solution you'd like

An implies_all option for Arg is what I'm interested in. But I would also add implies (singular) and implied_by. I believe this is similar to default_value_if except that it is for flags.

Alternatives, if applicable

I don't know of another convenient way to do this. Am I missing something?

Perhaps it should be named similarly to default_value_*? The default_value_* functions imply takes_value. Changing this is probably not an option. So it seems to me that the default_value_* space is too different. The word "implies" is intuitive to me.

[pksunkara]

On master branch, you should be able to do this with the following:

App::new("MyApp")
    .replace("--save-all", &["--save-image", "--save-stats", "--save-text"])
    .arg(Arg::with_name("save_all")
        .long("save-all"))
    .arg(Arg::with_name("save_image")
        .long("save-image"))
    .arg(Arg::with_name("save_stats")
        .long("save-stats"))
    .arg(Arg::with_name("save_text")
        .long("save-text"))

[kbknapp]

@camsteffen once you can confirm the proposed solution works for you and meats your intent we can close the issue 😄

[camsteffen]

Interesting, that might work. Just some minor concerns.

The example given in the docs for replace is to create what I would call a "subcommand alias" where "install" is an alias for "module install". For a "subcommand alias" I would expect it to only work when the alias is the first or only argument. But for my use case, "save-all" can appear anywhere in the arguments. This should be considered and documented better.

I would expect my use case to be possible at the Arg level instead of App, but oh well.

Ideally, I would like the implies functionality to show in the help text for that Arg. But again, this is less important.

[kbknapp]

@camsteffen we're in the process of going through all docs, so I'll make sure that one gets some additional explanation to make it clear that it's not just for subcommands. You can think of it literally replacing/inserting the left hand side item (--save-all) with all of the right hand side items (--save-image --save-stats --save-text)prior to parsing.

So the CLI invocation goes from:

$ app --save-all

  # TO

$ app ---save-image --save-stats --save-text

You're correct it doesn't automatically add verbiage to the help message of --save-all that it sets the others, for now that is left up to the consumer to add.

[camsteffen]

@kbknapp Sounds good.

I'm still wondering about the example for replace though. Should app module install become app module module install?

[kbknapp]

replace is not an alias function. We will find a better way to word the example, but the example isn't creating an alias, it's creating a "shortcut" so to speak.

Imagine app has one subcommand module, and app module has a subcommand install. What the example is doing is creating a fake second subcommand of app called install which actually invokes the app module install subcommand. rustup does something similar, just without the replace functionality. While it's similar to an alias, aliases don't let you inject and thus invoke further into the CLI. Aliases only let you refer to a subcommand on the same level by a different name. For example, in our app example, if we gave the module subcommand and alias of mod, it would mean both of these are functionally equivalent:

$ app module install
$ app mod install

Likewise, if instead of replace we'd used an alias, and gave module an alias of install, the following would be functionally equivalent (although nonsensical):

$ app module install
$ app install install

Hopefully this clears it up a little more.

I'm going to close this issue, but feel free to continue asking questions if you need more explanation 😉

[pksunkara]

Ideally, I would like the implies functionality to show in the help text for that Arg.

You're correct it doesn't automatically add verbiage to the help message of --save-all that it sets the others, for now that is left up to the consumer to add.

That's true for for all the other conditions too. requires*, conflicts* similarly doesn't set any help text.

replacing/inserting the left hand side item with all of the right hand side items prior to parsing.

It does the replacing during parsing which allows to let it work only on certain apps (or subcommands)

app module install would not change because replacer is checking for install on the app App. Here install appears at the module subcommand App.

I am actually using it like the below in one of the CLI tools I am working on.

App::new("app")
    .replace("ll", &["ls", "-l"])
    .replace("la", &["ls", "-a"])
    .subcommand(App::new("ls")
        .arg(Arg::new("all").short('a'))
        .arg(Arg::new("long").short('l'))

[camsteffen]

That's true for for all the other conditions too. requires*, conflicts* similarly doesn't set any help text.

Ok, makes sense.

app module install would not change because replacer is checking for install on the app App. Here install appears at the module subcommand App.

Ah, that answers my question!

Ok, I'm happy with replace 😃. Will it be in a release soon?

[kbknapp]

Will it be in a release soon?

You can already use it via git dependency in Cargo.toml

[dependencies]
clap = { git = "https://github.com/clap-rs/clap" }

You can specify by branch or version (replace is in version 3.0.0-beta.1). Once we finish up the 3.0 release, it will be uploaded to crates.io as well.

[camsteffen]

Alas, I finally tried it and it did not work as expected.

let matches = clap::App::new("MyApp")
    .replace("--save-all", &["--save-a", "--save-b"])
    .arg(Arg::with_name("flag").short('f'))
    .arg(Arg::with_name("save_all").long("save-all"))
    .arg(Arg::with_name("save_a").long("save-a"))
    .arg(Arg::with_name("save_b").long("save-b"))
    .get_matches_from(&["-f", "--save-all"]);
assert!(matches.is_present("flag")); // fails here
assert!(matches.is_present("save_a"));
assert!(matches.is_present("save_b"));

[kbknapp]

You're missing the binary name. It should be:

    .get_matches_from(&["myapp", "-f", "--save-all"]);

If you don't want to include a binary name you must use AppSettings::NoBinaryName

[camsteffen]

🤦