Precedence of allow_hyphen_values and last

[mamekoro]

Clap v4.3.0 introduced this change:

(parser) Ensure value_terminator has higher precedence than allow_hyphen_values

Are there any plans to introduce similar changes for #[arg(last = true)]?
I would like last to take precedence over allow_hyphen_values.

Here is an example with clap 4.3.3:

use clap::Parser;

fn main() {
    println!("{:?}", Args::parse());
}

#[derive(Clone, Debug, Parser)]
pub struct Args {
    /// Options for 'docker run'.
    #[arg(allow_hyphen_values = true)]
    pub opts: Vec<String>,

    /// Command to be executed in a container and its arguments
    #[arg(allow_hyphen_values = true, last = true)]
    pub cmdline: Vec<String>,
}

I would like to distinguish between opts and cmdline by separating them with a --. However, it does not work because allow_hyphen_values has higher precedence than last as of Clap 4.3.3.

Here are some tests in Bash:

$ alias run='cargo run --quiet --'

# `last = true` is not working.
# opts should be ["--name", "test"] and cmdline should be ["ls", "-l"].
$ run --name test -- ls -l
Args { opts: ["--name", "test", "--", "ls", "-l"], cmdline: [] }

# `last = true` is not working.
# opts should be ["--name", "test"], and cmdline should be [].
$ run --name test --
Args { opts: ["--name", "test", "--"], cmdline: [] }

# The followings are OK.

$ run --name test
Args { opts: ["--name", "test"], cmdline: [] }

$ run -- ls -l
Args { opts: [], cmdline: ["ls", "-l"] }

I also tried value_terminator = "--", but it is not successful.

#[derive(Clone, Debug, Parser)]
pub struct Args {
    // `value_terminator` has been added
    #[arg(allow_hyphen_values = true, value_terminator = "--")]
    pub opts: Vec<String>,

    // `last` has been removed
    #[arg(allow_hyphen_values = true)]
    pub cmdline: Vec<String>,
}

$ alias run='cargo run --quiet --'

# OK
$ run --name test -- ls -l
Args { opts: ["--name", "test"], cmdline: ["ls", "-l"] }

# All of the following are unexpected results.

# There is no '--' in the arguments. I don't know what to expect.
# At least, this is not the expected result.
$ run --name test
Args { opts: ["--name"], cmdline: ["test"] }

# cmdline should be [].
$ run --name test --
Args { opts: ["--name", "test"], cmdline: ["--"] }

# opts should be [], and cmdline should be ["ls", "-l"].
$ run -- ls -l
Args { opts: ["ls"], cmdline: ["-l"] }

# There is no '--' in the arguments. I don't know what to expect.
# At least, this is not the expected result.
$ run ls -l
Args { opts: ["ls"], cmdline: ["-l"] }

I prefer last to value_terminator = "--" because last always requires --, which makes the command line clearer and easier for me to understand. value_terminator = "--" is confusing when there is no -- as in the above tests.

So I want to use last, but then I face the precedence problem.

Would you consider allowing last to take precedence over allow_hyphen_values?

[epage]

The prior change (#4919, #4924) required some analysis to determine the scope and depth of impact for whether it can be done in a minor release, needs to wait for a major, or whether it shouldn't be done at all.

I'll have to step through this when I have more focus time to figure out where this change lands in all of that.

[epage]

For anything further on this, I'd recommend creating an issue. This likely needs further consideration before implementing and I'd like to have an Issue so I don't lose track of it.

[epage]

4.3.19 is out with a fix for the value_termiantor bugs (#5037)

[mamekoro]

Thanks, I opened a new issue: #5039