use serde::{
Deserialize, Deserializer,
de::{MapAccess, SeqAccess, Visitor, value::MapAccessDeserializer},
};
pub(crate) struct Object<T>(pub T);
impl<'de, T: Deserialize<'de>> Deserialize<'de> for Object<T> {
fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
struct ObjectVisitor<T>(std::marker::PhantomData<T>);
impl<'de, T: Deserialize<'de>> Visitor<'de> for ObjectVisitor<T> {
type Value = Object<T>;
fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
formatter.write_str("a JSON object")
}
fn visit_map<M: MapAccess<'de>>(self, map: M) -> Result<Self::Value, M::Error> {
T::deserialize(MapAccessDeserializer::new(map)).map(Object)
}
}
deserializer.deserialize_map(ObjectVisitor(std::marker::PhantomData))
}
}
pub(crate) struct Ignored;
impl<'de> Deserialize<'de> for Ignored {
fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
struct IgnoredVisitor;
impl<'de> Visitor<'de> for IgnoredVisitor {
type Value = Ignored;
fn expecting(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
formatter.write_str("a JSON value")
}
fn visit_bool<E>(self, _: bool) -> Result<Ignored, E> {
Ok(Ignored)
}
fn visit_i64<E>(self, _: i64) -> Result<Ignored, E> {
Ok(Ignored)
}
fn visit_u64<E>(self, _: u64) -> Result<Ignored, E> {
Ok(Ignored)
}
fn visit_f64<E>(self, _: f64) -> Result<Ignored, E> {
Ok(Ignored)
}
fn visit_str<E>(self, _: &str) -> Result<Ignored, E> {
Ok(Ignored)
}
fn visit_string<E>(self, _: String) -> Result<Ignored, E> {
Ok(Ignored)
}
fn visit_unit<E>(self) -> Result<Ignored, E> {
Ok(Ignored)
}
fn visit_none<E>(self) -> Result<Ignored, E> {
Ok(Ignored)
}
fn visit_seq<S: SeqAccess<'de>>(self, mut sequence: S) -> Result<Ignored, S::Error> {
while sequence.next_element::<Ignored>()?.is_some() {}
Ok(Ignored)
}
fn visit_map<M: MapAccess<'de>>(self, mut map: M) -> Result<Ignored, M::Error> {
while map.next_key::<String>()?.is_some() {
map.next_value::<Ignored>()?;
}
Ok(Ignored)
}
}
deserializer.deserialize_any(IgnoredVisitor)
}
}
pub(crate) struct Optional<T>(pub Option<T>);
impl<T> Default for Optional<T> {
fn default() -> Self {
Self(None)
}
}
impl<'de, T: Deserialize<'de>> Deserialize<'de> for Optional<T> {
fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {
#[derive(Deserialize)]
#[serde(untagged)]
enum Field<T> {
Known(T),
Ignored(Ignored),
}
Ok(Self(match Field::deserialize(deserializer)? {
Field::Known(value) => Some(value),
Field::Ignored(_) => None,
}))
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn typed_discard_rejects_number_overflow_and_excessive_nesting() {
for input in [
"1e400",
"{\"unknown\":[1e400]}",
"{\"number\":1e400,\"number\":null}",
] {
assert!(serde_json::from_str::<Ignored>(input).is_err());
}
for input in [
"18446744073709551616",
"-9223372036854775809",
"{\"unknown\":[null,true,0,1.5,\"s\"]}",
] {
assert!(serde_json::from_str::<Ignored>(input).is_ok());
}
let deep = format!("{}null{}", "[".repeat(200), "]".repeat(200));
assert!(serde_json::from_str::<Ignored>(&deep).is_err());
}
}