Serialization and deserialization byte array (Vec<u8>) to/from json in Rust as Base64 string using Serde

rust_serde_base64_bytes.rs

use serde::{Deserialize, Deserializer, Serialize, Serializer};

#[derive(Serialize, Deserialize, Debug)]
pub struct Foo {
    #[serde(serialize_with = "as_base64", deserialize_with = "from_base64")]
    bytes: Vec<u8>,
}

fn as_base64<T: AsRef<[u8]>, S: Serializer>(val: &T, serializer: S) -> Result<S::Ok, S::Error> {
    serializer.serialize_str(&base64::encode(val))
}

fn from_base64<'de, D: Deserializer<'de>>(deserializer: D) -> Result<Vec<u8>, D::Error> {
    use serde::de;

    <&str>::deserialize(deserializer).and_then(|s| {
        base64::decode(s)
            .map_err(|e| de::Error::custom(format!("invalid base64 string: {}, {}", s, e)))
    })
}

fn main() {
    println!(
        "{:?}",
        serde_json::from_str::<Foo>(r#"{"bytes":"AQIDBAUGBwgJCgsMDQ4PEA=="}"#).unwrap()
    );
    println!(
        "{}",
        serde_json::to_string(&Foo {
            bytes: vec![16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
        })
        .unwrap()
    );
}

Based on the discussion at serde#661.

The output of this code is:

Foo { bytes: [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16] }
{"bytes":"EA8ODQwLCgkIBwYFBAMCAQA="}

what about Option<Vec>