Feature request: better build info tools (which features, codegen a binary was compiled with)

[jonathanstrong]

Rust Version

rustc 1.31.0-nightly (bef62ccdd 2018-10-16)

Affected Version of clap

2.32.0

Bug or Feature Request Summary

I often find myself checking which version of a binary I compiled, between versions, crate features and codegen options. I wrote some code below which I am using via the App::about method to provide build info for my clap-generated -h printout. (Like vim --version, but much less info).

pub fn build_info() -> String {
    let indent = "    ";
    format!("\r\n\
        BUILD:\r\n\
        {}{}\r\n\r\n\
        CODEGEN:\r\n\
        {}{}",
        indent, features().join(" "),
        indent, codegen().join(" "))
}

fn codegen() -> Vec<&'static str> {
    let mut flags = Vec::new();
    macro_rules! check_cpu {
        ($($target:expr),*) => {{
            $(
                #[cfg(target_feature = $target)]
                flags.push($target);
            )*
        }}
    }

    check_cpu!("aes", "avx", "avx2", "avx512bw", "avx512cd", "avx512dq", "avx512f", "avx512vl", "bmi1",
               "bmi2", "fma", "fxsr", "lzcnt", "mmx", "pclmulqdq", "popcnt", "rdrand", "rdseed", "sse",
               "sse2", "sse3", "sse4.1", "sse4.2", "ssse3", "xsave", "xsavec", "xsaveopt", "xsaves");

    flags.sort_unstable();
    flags.dedup();
    flags
}

fn features() -> Vec<&'static str> {
    macro_rules! feat_list {
        ($($feat:expr),*) => {
            vec![
                $(
                    #[cfg(feature = $feat)]
                    $feat,
                )*
            ]
        }
    }

    let mut flags = feat_list!("feat-one", "feat-two");

    #[cfg(debug_assertions)]
    flags.push("debug_assertions");

    flags.sort_unstable();
    flags.dedup();
    flags
}

// ...

fn main()
    let build_info = mylib::build_info();
    let args: ArgMatches = App::new("my-binary")
        .version(crate_version!())
        .about(build_info.as_str())
        // ...

This is ok, but unfortunately it needs to be manually maintained as new features are added, etc. It occurred to me that perhaps clap would be a good fit for this kind of functionality, and I didn't see anything in the docs about providing build info. Have you considered adding tools for tracking features, codegen options, etc.?

[epage]

This also has overlap with

• https://github.com/sharkdp/bugreport
• https://github.com/rust-cli/human-panic

[epage]

https://crates.io/crates/shadow-rs seems to also fill a similar role

• Detect target features baoyachi/shadow-rs#69
• Distinguish between clap::App::version and clap::App::long_version baoyachi/shadow-rs#70