test.rs

    let json_files = fs::read_dir("metadata.lux")?
                         .take_while(|e| e.is_ok())
                         .map(|e| e.unwrap().path())
                         .take_while(|p| true);
                         //.take_while(|p| p.extension().unwrap() == "json");

    for p in json_files {
        println!(":: {:?} {} {:?} {:?}", p, p.ends_with("json"), p.extension().unwrap(), p.extension().unwrap() == "json");
    }

// prints:
:: "metadata.lux/vkquake.files" false "files" false
:: "metadata.lux/vkquake.json" false "json" true


    let json_files = fs::read_dir("metadata.lux")?
                         .take_while(|e| e.is_ok())
                         .map(|e| e.unwrap().path())
                         .take_while(|p| p.extension().unwrap() == "json");
                         //.take_while(|p| true);

    for p in json_files {
        println!(":: {:?} {} {:?} {:?}", p, p.ends_with("json"), p.extension().unwrap(), p.extension().unwrap() == "json");
    }

// prints nothig!