Rust build.rs file to compile SASS to CSS

build.rs

use std::ffi::OsStr;
use std::fs::File;
use std::io::Write;
use std::path::Path;

use sass_rs;
use walkdir::{DirEntry, WalkDir};

const SASS_DIR: &str = "assets/sass";
const CSS_DIR: &str = "static/css";

fn is_ignored(entry: &DirEntry) -> bool {
    entry
        .file_name()
        .to_str()
        .map(|s| s.starts_with("_"))
        .unwrap_or(false)
}

fn main() {
    if !Path::new(CSS_DIR).is_dir() {
        std::fs::create_dir(CSS_DIR);
    }

    let walker = WalkDir::new(SASS_DIR).into_iter();

    for entry in walker.filter_entry(|e| !is_ignored(e)) {
        let entry = entry.unwrap();
        let path = entry.path();
        if !path.is_file() {
            continue;
        }
        if let Some(ext) = path.extension() {
            if ext != "sass" {
                continue;
            }
            let content = sass_rs::compile_file(path, Default::default())
                .unwrap_or_else(|err| panic!("Error compiling {}: {}", path.display(), err));

            let stripped_path = path.strip_prefix(SASS_DIR).unwrap();

            let css_filename = stripped_path
                .file_stem()
                .unwrap()
                .to_str()
                .unwrap()
                .to_owned()
                + ".css";
            let css_path = stripped_path.parent().unwrap().join(css_filename);
            let css_path = Path::new(CSS_DIR).join(css_path);
            let mut css_file = File::create(css_path).unwrap();
            css_file.write_all(content.as_bytes()).unwrap();
        }
    }
}

Cargo.toml

[build-dependencies]
sass-rs = "0.2"
walkdir = "2"