build.rs

use std::env;
use std::path::Path;
use std::process::Command;
use std::{fs, io};

fn main() {
    let out_dir = env::var("OUT_DIR").unwrap();

    // Tell Cargo that if anything in the frontend/ directory changes, it should
    // rerun this build script.
    println!("cargo::rerun-if-changed=frontend");

    // Copy the entire frontend directory into the OUT_DIR. We need to do this
    // because building the frontend code requires installing node_modules and
    // generating files in dist/, and Cargo will refuse to build if build.rs
    // "dirties" the source directory.
    copy_dir_all("frontend", &format!("{}/frontend", &out_dir))
        .expect("copying frontend code to OUT_DIR failed");

    // Run npm install for frontend/ (in the OUT_DIR)
    let status = Command::new("npm")
        .args(&["install"])
        .current_dir(&format!("{}/frontend", &out_dir))
        .status()
        .expect("failed to execute 'npm install'");

    if !status.success() {
        panic!("'npm install' failed with exit code: {}", status);
    }

    // Run npm run build for frontend/ (in the OUT_DIR)
    let status = Command::new("npm")
        .args(&["run", "build"])
        .current_dir(&format!("{}/frontend", &out_dir))
        .status()
        .expect("failed to execute 'npm run build'");

    if !status.success() {
        panic!("'npm run build' failed with exit code: {}", status);
    }
}

fn copy_dir_all(src: impl AsRef<Path>, dst: impl AsRef<Path>) -> io::Result<()> {
    fs::create_dir_all(&dst)?;
    for entry in fs::read_dir(src)? {
        let entry = entry?;
        let file_type = entry.file_type()?;

        if file_type.is_dir() {
            copy_dir_all(entry.path(), dst.as_ref().join(entry.file_name()))?;
        } else if file_type.is_symlink() {
            let resolved_target = fs::canonicalize(entry.path())?;

            if resolved_target.is_dir() {
                copy_dir_all(resolved_target, dst.as_ref().join(entry.file_name()))?;
            } else {
                fs::copy(resolved_target, dst.as_ref().join(entry.file_name()))?;
            }
        } else {
            fs::copy(entry.path(), dst.as_ref().join(entry.file_name()))?;
        }
    }
    Ok(())
}