Implement Serialize and Deserialize

[zhengyi-yang]

It's helpful to implement serde's Serialize and Deserialize for Vec32

[ryanavella]

I agree, it would be a useful trait to expose. Some users don't want to bring in all of Serde's machinery just to use Vec32, so we will need to either hide it behind a feature-gate or mark it as an optional dependency. And we want to make sure the semver requirements aren't overly restricted.

I think this is conventionally how it is done in other popular crates' Cargo.toml:

[dependencies]
serde = { version = "1", optional = true, default-features = false }

If you want a workaround for the short term, you can use serde_derive like this:

use mediumvec::Vec32;
use serde::{de::DeserializeOwned, Deserialize, Deserializer, Serialize, Serializer};
use serde_derive::{Deserialize, Serialize};

fn deserialize_vec32<'de, D, T>(de: D) -> Result<Vec32<T>, D::Error>
where
    D: Deserializer<'de>,
    T: Serialize + DeserializeOwned,
{
    Ok(Vec32::from_vec(Deserialize::deserialize(de)?))
}

fn serialize_vec32<S, T>(v: &Vec32<T>, s: S) -> Result<S::Ok, S::Error>
where
    S: Serializer,
    T: Serialize,
{
    s.collect_seq(v)
}

#[derive(Deserialize, Serialize)]
struct Foo<T>
where
    T: Serialize + DeserializeOwned,
{
    #[serde(deserialize_with = "deserialize_vec32")]
    #[serde(serialize_with = "serialize_vec32")]
    v: Vec32<T>,
}

[zhengyi-yang]

Thanks @ryanavella !