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#![allow(clippy::trait_duplication_in_bounds)] // https://github.com/rust-lang/rust-clippy/issues/8757
use serde::{Deserialize, Deserializer};
use std::fmt::{self, Display};
use std::marker::PhantomData;
use std::str::FromStr;
pub struct NumberVisitor<T> {
marker: PhantomData<T>,
}
impl<'de, T> serde::de::Visitor<'de> for NumberVisitor<T>
where
T: TryFrom<u64> + TryFrom<i64> + FromStr,
<T as TryFrom<u64>>::Error: Display,
<T as TryFrom<i64>>::Error: Display,
<T as FromStr>::Err: Display,
{
type Value = T;
fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
formatter.write_str("an integer or string")
}
fn visit_u64<E>(self, v: u64) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
T::try_from(v).map_err(serde::de::Error::custom)
}
fn visit_i64<E>(self, v: i64) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
T::try_from(v).map_err(serde::de::Error::custom)
}
fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
v.parse().map_err(serde::de::Error::custom)
}
}
fn deserialize_integer_or_string<'de, D, T>(deserializer: D) -> Result<T, D::Error>
where
D: Deserializer<'de>,
T: TryFrom<u64> + TryFrom<i64> + FromStr,
<T as TryFrom<u64>>::Error: Display,
<T as TryFrom<i64>>::Error: Display,
<T as FromStr>::Err: Display,
{
deserializer.deserialize_any(NumberVisitor {
marker: PhantomData,
})
}
#[derive(Deserialize, Debug)]
pub struct Struct {
#[serde(deserialize_with = "deserialize_integer_or_string")]
#[allow(dead_code)]
pub i: i64,
}
#[test]
fn test() {
let j = r#" {"i":100} "#;
println!("{:?}", serde_json::from_str::<Struct>(j).unwrap());
let j = r#" {"i":"100"} "#;
println!("{:?}", serde_json::from_str::<Struct>(j).unwrap());
}