rust - 有没有办法对多个语句使用 cfg(feature) 检查？

Question

有没有办法尽量减少以下功能检查？

#[cfg(feature = "eugene")]
pub mod eugene_set_steam_id;
#[cfg(feature = "eugene")]
pub mod eugene_balance;
#[cfg(feature = "eugene")]
pub mod eugene_force_map;
#[cfg(feature = "eugene")]
pub mod eugene_rating;
#[cfg(feature = "eugene")]
pub mod eugene_stat;
#[cfg(feature = "eugene")]
pub mod eugene_steam_id;
#[cfg(feature = "eugene")]
pub mod eugene_top;

类似于:

#[cfg(feature = "eugene")] {
    pub mod eugene_set_steam_id;
    pub mod eugene_balance;
    pub mod eugene_force_map;
    pub mod eugene_rating;
    pub mod eugene_stat;
    pub mod eugene_steam_id;
    pub mod eugene_top;
}

这会更好地传达意义并且更符合人体工程学。

Answer 1

cfg-if crate提供 cfg-if! 宏来执行您想要的操作:

#[macro_use]
extern crate cfg_if;

cfg_if! {
    if #[cfg(feature = "eugene")] {
        pub mod eugene_set_steam_id;
        pub mod eugene_balance;
        pub mod eugene_force_map;
        pub mod eugene_rating;
        pub mod eugene_stat;
        pub mod eugene_steam_id;
        pub mod eugene_top;
    } else {
    }
}

事实上，它甚至用你的话来描述自己:

A macro to ergonomically define an item depending on a large number of #[cfg] parameters. Structured like an if-else chain, the first matching branch is the item that gets emitted.