/// Provides serialization and deserialization functions which should use a default
/// string instead of `null` on the wire.
#[allow(unused_macros)]
macro_rules! optional_string {
($n:ident : $s:tt) => {
pub mod $n {
use serde::de::value::StringDeserializer;
use serde::{Serialize, Serializer, Deserialize, Deserializer};
/// The string which represents `null` on the wire.
pub static DEFAULT: &'static str = $s;
/// Serialize an optional value, replacing `None` with the module-specified default.
pub fn serialize<S: Serializer, T: Serialize>(opt: &Option<T>, s: S) -> Result<S::Ok, S::Error> {
match *opt {
None => s.serialize_str(DEFAULT),
Some(ref value) => s.serialize_some(value),
}
}
/// Deserialize a string, replacing the module-specified default with `None`.
pub fn deserialize<D: Deserializer, T: Deserialize>(d: D) -> Result<Option<T>, D::Error> {
let s = String::deserialize(d)?;
if s == DEFAULT {
Ok(None)
} else {
T::deserialize(s.into_deserializer()).map(Some)
}
}
}
}
}
/// Generate a `FromStr` implementation which uses serde's value deserializer.
///
/// # Usage
/// For an already-defined type, add deserialization with `fromstr_deserialize!(Type)`.
/// This will create an implementation of `std::str::FromStr` where `Err=String`, containing
/// the error message returned by the deserializer.
///
/// To create a deserialization that uses a custom error type, instead write
/// `fromstr_deserialize!(Type, Err = YourError)`. This requires
/// `YourError: From<::serde::de::value::Error>`.
macro_rules! fromstr_deserialize {
($t:ident) => {
impl ::std::str::FromStr for $t {
type Err = String;
fn from_str(s: &str) -> Result<Self, Self::Err> {
use std::string::ToString;
use serde::Deserialize;
use serde::de::IntoDeserializer;
use serde::de::value;
$t::deserialize(s.into_deserializer()).map_err(|e: value::Error| e.to_string())
}
}
};
($t:ident, Err = $err:ident) => {
impl ::std::str::FromStr for $t {
type Err = $err;
fn from_str(s: &str) -> Result<Self, Self::Err> {
use serde::Deserialize;
use serde::de::value::{self, ValueDeserializer};
$t::deserialize(s.into_deserializer()).map_err(|e: value::Error| $err::from(e))
}
}
}
}