build.rs

use std::env;
use std::error::Error;
use std::fs::File;
use std::io::Write as _;
use std::path::Path;

fn main() -> Result<(), Box<dyn Error>> {
    let out_dir = env::var("OUT_DIR").expect("OUT_DIR is set for build scripts");
    let dest_path = Path::new(&out_dir).join("constants.gen.rs");
    let mut f = File::create(dest_path)?;

    let target = env::var("TARGET").expect("TARGET is set for build scripts");
    let mut target_bits = target.split('-');

    // https://rust-lang.github.io/rfcs/0131-target-specification.html#detailed-design
    let mut arch = target_bits.next().expect("TARGET triple has an arch");
    let _vendor = target_bits.next();
    let platform = target_bits.next().expect("TARGET triple has a platform");

    if platform == "darwin" && arch == "aarch64" {
        arch = "arm64"; // enforce Darwin naming conventions
    }

    writeln!(f, "/// The platform identifier")?;
    writeln!(f, "pub const PLATFORM: &str = \"{platform}\";")?;
    writeln!(f, "/// The CPU architecture identifier")?;
    writeln!(f, "pub const ARCH: &str = \"{arch}\";")?;
    writeln!(f, "/// The user agent for sentry events")?;
    writeln!(f, "pub const USER_AGENT: &str = \"sentry-cli/{arch}\";")?;
    println!("cargo:rerun-if-changed=build.rs\n");

    Ok(())
}