Allow visible aliases for PossibleValue

[dbrgn]

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Clap Version

4.0.18

Describe your use case

Tealdeer has a parameter -p, --platform <PLATFORM> to select the platform. For historic reasons, this list must include "osx", but should also include the alias "macos". This alias should not be hidden, but should be visible.

With Clap 3, this was implemented using FromStr:

#[derive(Debug, Eq, PartialEq, Copy, Clone, Serialize, Deserialize)]
#[serde(rename_all = "lowercase")]
#[allow(dead_code)]
pub enum PlatformType {
    Linux,
    OsX,
    SunOs,
    Windows,
    Android,
}

impl str::FromStr for PlatformType {
    type Err = anyhow::Error;

    fn from_str(s: &str) -> Result<Self, Self::Err> {
        match s {
            "linux" => Ok(Self::Linux),
            "osx" | "macos" => Ok(Self::OsX),
            "sunos" => Ok(Self::SunOs),
            "windows" => Ok(Self::Windows),
            "android" => Ok(Self::Android),
            other => Err(anyhow!(
                "Unknown OS: {}. Possible values: linux, macos, osx, sunos, windows, android",
                other
            )),
        }
    }
}

    /// Override the operating system
    #[clap(
        short = 'p',
        long = "platform",
        possible_values = ["linux", "macos", "windows", "sunos", "osx", "android"],
    )]
    pub platform: Option<PlatformType>,

With Clap 4, I tried to migrate to EnumValueParser:

impl clap::ValueEnum for PlatformType {
    fn value_variants<'a>() -> &'a [Self] {
        &[Self::Linux, Self::OsX, Self::Windows, Self::SunOs, Self::Android]
    }

    fn to_possible_value<'a>(&self) -> Option<clap::builder::PossibleValue> {
        match self {
            Self::Linux => Some(clap::builder::PossibleValue::new("linux")),
            Self::OsX => Some(clap::builder::PossibleValue::new("osx").alias("macos")),
            Self::Windows => Some(clap::builder::PossibleValue::new("windows")),
            Self::SunOs => Some(clap::builder::PossibleValue::new("sunos")),
            Self::Android => Some(clap::builder::PossibleValue::new("android")),
        }
    }
}

This works, but the alias is not visible in help output or error messages.

Describe the solution you'd like

Since Command has both .alias(...) and .visible_alias(...), would this be possible for PossibleValue as well?

Alternatives, if applicable

No response

Additional Context

No response