watt/build.rs

use std::env;
use std::fs;
use std::path::PathBuf;

const MULTICALL_NAMES: &[&str] = &["cpu", "power"];

fn main() -> Result<(), Box<dyn std::error::Error>> {
    println!("cargo:rerun-if-changed=build.rs");

    let out_dir = PathBuf::from(env::var("OUT_DIR")?);
    let target = out_dir
        .parent() // target/debug/build/<pkg>-<hash>/out
        .and_then(|p| p.parent()) // target/debug/build/<pkg>-<hash>
        .and_then(|p| p.parent()) // target/debug/
        .ok_or("failed to find target directory")?;

    let main_binary_name = env::var("CARGO_PKG_NAME")?;

    let main_binary_path = target.join(&main_binary_name);

    let mut errored = false;

    for name in MULTICALL_NAMES {
        let hardlink_path = target.join(name);

        if hardlink_path.exists() {
            if hardlink_path.is_dir() {
                fs::remove_dir_all(&hardlink_path)?;
            } else {
                fs::remove_file(&hardlink_path)?;
            }
        }

        if let Err(error) = fs::hard_link(&main_binary_path, &hardlink_path) {
            println!(
                "cargo:warning=failed to create hard link '{path}': {error}",
                path = hardlink_path.display(),
            );
            errored = true;
        }
    }

    if errored {
        println!(
            "cargo:warning=this often happens because the target binary isn't built yet, try running `cargo build` again"
        );
        println!("cargo:warning=keep in mind that this is for development purposes only");
    }

    Ok(())
}