among 0.2.0

A general purpose sum type with three cases: the enum `Among` with variants `Left`, `Middle` and `Right`. A three-way counterpart to `Either`, with `no_std`, `serde`, `futures` and `tokio` integrations.
Documentation 
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//! Untagged serialization/deserialization support for `Option<Among<L, M, R>>`.
//!
//! `Among` uses default, externally-tagged representation.
//! However, sometimes it is useful to support several alternative types.
//! For example, we may have a field which is generally `Map<String, i32>`
//! but in typical cases `Vec<String>` would suffice, too.
//!
//! ```rust
//! # fn main() -> Result<(), Box<dyn std::error::Error>> {
//! use among::Among;
//! use std::collections::HashMap;
//!
//! #[derive(serde::Serialize, serde::Deserialize, Debug)]
//! #[serde(transparent)]
//! struct IntOrString {
//!     #[serde(with = "among::serde_untagged_optional")]
//!     inner: Option<Among<Vec<String>, Box<str>, HashMap<String, i32>>>
//! }
//!
//! // serialization
//! let data = IntOrString {
//!     inner: Some(Among::Left(vec!["Hello".to_string()]))
//! };
//! // notice: no tags are emitted.
//! assert_eq!(serde_json::to_string(&data)?, r#"["Hello"]"#);
//!
//! // deserialization
//! let data: IntOrString = serde_json::from_str(
//!     r#"{"a": 0, "b": 14}"#
//! )?;
//! println!("found {:?}", data);
//! # Ok(())
//! # }
//! ```

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

#[derive(Serialize, Deserialize)]
#[serde(untagged)]
enum Among<L, M, R> {
  Left(L),
  Middle(M),
  Right(R),
}

pub fn serialize<L, M, R, S>(
  this: &Option<super::Among<L, M, R>>,
  serializer: S,
) -> Result<S::Ok, S::Error>
where
  S: Serializer,
  L: Serialize,
  M: Serialize,
  R: Serialize,
{
  let untagged = match this {
    Some(super::Among::Left(left)) => Some(Among::Left(left)),
    Some(super::Among::Middle(middle)) => Some(Among::Middle(middle)),
    Some(super::Among::Right(right)) => Some(Among::Right(right)),
    None => None,
  };
  untagged.serialize(serializer)
}

pub fn deserialize<'de, L, M, R, D>(
  deserializer: D,
) -> Result<Option<super::Among<L, M, R>>, D::Error>
where
  D: Deserializer<'de>,
  L: Deserialize<'de>,
  M: Deserialize<'de>,
  R: Deserialize<'de>,
{
  match Option::deserialize(deserializer) {
    Ok(Some(Among::Left(left))) => Ok(Some(super::Among::Left(left))),
    Ok(Some(Among::Right(right))) => Ok(Some(super::Among::Right(right))),
    Ok(Some(Among::Middle(middle))) => Ok(Some(super::Among::Middle(middle))),
    Ok(None) => Ok(None),
    Err(error) => Err(error),
  }
}