preserves 4.996.0

Implementation of the Preserves serialization format via serde.
Documentation 
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//! Serde support for serializing Rust data as Preserves symbols.
//!
//! Serde doesn't include symbols in its data model, so we do some somewhat awful tricks to
//! force things to come out the way we want them.
//!
//! # Example
//!
//! Either use [Symbol] directly in your data types, or annotate [String]-valued fields that
//! you want to (en|de)code as Preserves `Symbol`s with `#[serde(with = "preserves::symbol")]`:
//!
//! ```rust
//! #[derive(serde::Serialize, serde::Deserialize)]
//! struct Example {
//!   sym1: preserves::symbol::Symbol,
//!   #[serde(with = "preserves::symbol")]
//!   sym2: String,
//! }
//! ```

use crate::value::{IOValue, NestedValue};

/// Wrapper for a string to coerce its Preserves-serialization to `Symbol`.
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Clone)]
pub struct Symbol(pub String);

impl serde::Serialize for Symbol {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        IOValue::symbol(&self.0).serialize(serializer)
    }
}

impl<'de> serde::Deserialize<'de> for Symbol {
    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
    where
        D: serde::Deserializer<'de>,
    {
        let v = IOValue::deserialize(deserializer)?;
        let s = v
            .value()
            .as_symbol()
            .ok_or_else(|| serde::de::Error::custom("Expected symbol"))?;
        Ok(Symbol(s.clone()))
    }
}

#[doc(hidden)]
pub fn serialize<S>(s: &str, serializer: S) -> Result<S::Ok, S::Error>
where
    S: serde::Serializer,
{
    use serde::Serialize;
    Symbol(s.to_string()).serialize(serializer)
}

#[doc(hidden)]
pub fn deserialize<'de, D>(deserializer: D) -> Result<String, D::Error>
where
    D: serde::Deserializer<'de>,
{
    use serde::Deserialize;
    Symbol::deserialize(deserializer).map(|v| v.0)
}