⚙️ cfg-expr

A parser and evaluator for Rust cfg() expressions.

Alternatives

Usage

use cfg_expr::{targets::get_target_by_triple, Expression, Predicate};

fn main() {
    let specific = Expression::parse(
        r#"all(
            target_os = "windows",
            target_arch = "x86",
            windows,
            target_env = "msvc",
            target_feature = "fxsr",
            target_feature = "sse",
            target_feature = "sse2",
            target_pointer_width = "32",
            target_endian = "little",
            not(target_vendor = "uwp"),
            feature = "cool_thing",
        )"#,
    )
    .unwrap();

    // cfg_expr includes a list of every builtin target in rustc (as of 1.40)
    let x86_win = get_target_by_triple("i686-pc-windows-msvc").unwrap();
    let x86_pentium_win = get_target_by_triple("i586-pc-windows-msvc").unwrap();
    let uwp_win = get_target_by_triple("i686-uwp-windows-msvc").unwrap();
    let mac = get_target_by_triple("x86_64-apple-darwin").unwrap();

    let avail_targ_feats = ["fxsr", "sse", "sse2"];

    // This will satisfy all requirements
    assert!(specific.eval(|pred| {
        match pred {
            Predicate::Target(tp) => tp.matches(x86_win),
            Predicate::TargetFeature(feat) => avail_targ_feats.contains(feat),
            Predicate::Feature(feat) => *feat == "cool_thing",
            _ => false,
        }
    }));

    // This won't, it doesnt' have the cool_thing feature!
    assert!(!specific.eval(|pred| {
        match pred {
            Predicate::Target(tp) => tp.matches(x86_pentium_win),
            Predicate::TargetFeature(feat) => avail_targ_feats.contains(feat),
            _ => false,
        }
    }));

    // This will *not* satisfy the vendor predicate
    assert!(!specific.eval(|pred| {
        match pred {
            Predicate::Target(tp) => tp.matches(uwp_win),
            Predicate::TargetFeature(feat) => avail_targ_feats.contains(feat),
            _ => false,
        }
    }));

    // This will *not* satisfy the vendor, os, or env predicates
    assert!(!specific.eval(|pred| {
        match pred {
            Predicate::Target(tp) => tp.matches(mac),
            Predicate::TargetFeature(feat) => avail_targ_feats.contains(feat),
            _ => false,
        }
    }));
}

Contributing

We welcome community contributions to this project.

Please read our Contributor Guide for more information on how to get started.

License

Licensed under either of

Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution