Struct serde_with::SetPreventDuplicates

pub struct SetPreventDuplicates<T>(_);

Ensure no duplicate values exist in a set.

By default serde has a last-value-wins implementation, if duplicate values for a set exist. Sometimes it is desirable to know when such an event happens, as the first value is overwritten and it can indicate an error in the serialized data.

This helper returns an error if two identical values exist in a set.

The implementation supports both the HashSet and the BTreeSet from the standard library.

Example

#[serde_as]
#[derive(Deserialize)]
struct Doc {
    #[serde_as(as = "SetPreventDuplicates<_>")]
    set: HashSet<usize>,
}

// Sets are serialized normally,
let s = r#"{"set": [1, 2, 3, 4]}"#;
let v = Doc {
    set: HashSet::from_iter(vec![1, 2, 3, 4]),
};
assert_eq!(v, serde_json::from_str(s).unwrap());

// but create an error if duplicate values, like the `1`, exist.
let s = r#"{"set": [1, 2, 3, 4, 1]}"#;
let res: Result<Doc, _> = serde_json::from_str(s);
assert!(res.is_err());

Trait Implementations

impl<'de, T, TAs> DeserializeAs<'de, BTreeSet<T, Global>> for SetPreventDuplicates<TAs>where TAs: DeserializeAs<'de, T>, T: Ord,

fn deserialize_as<D>(deserializer: D) -> Result<BTreeSet<T>, D::Error>where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<'de, T, TAs, S> DeserializeAs<'de, HashSet<T, S>> for SetPreventDuplicates<TAs>where TAs: DeserializeAs<'de, T>, T: Eq + Hash, S: BuildHasher + Default,

fn deserialize_as<D>(deserializer: D) -> Result<HashSet<T, S>, D::Error>where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<'de, T, TAs, S> DeserializeAs<'de, IndexSet<T, S>> for SetPreventDuplicates<TAs>where TAs: DeserializeAs<'de, T>, T: Eq + Hash, S: BuildHasher + Default,

fn deserialize_as<D>(deserializer: D) -> Result<IndexSet<T, S>, D::Error>where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T, TAs> SerializeAs<BTreeSet<T, Global>> for SetPreventDuplicates<TAs>where TAs: SerializeAs<T>,

fn serialize_as<S>(value: &BTreeSet<T>, serializer: S) -> Result<S::Ok, S::Error>where S: Serializer,

Serialize this value into the given Serde serializer.

impl<T, TAs, H> SerializeAs<HashSet<T, H>> for SetPreventDuplicates<TAs>where TAs: SerializeAs<T>, H: ?Sized + Sized,

fn serialize_as<S>( value: &HashSet<T, H>, serializer: S ) -> Result<S::Ok, S::Error>where S: Serializer,

Serialize this value into the given Serde serializer.

impl<T, TAs, H> SerializeAs<IndexSet<T, H>> for SetPreventDuplicates<TAs>where TAs: SerializeAs<T>, H: ?Sized + Sized,

fn serialize_as<S>( value: &IndexSet<T, H>, serializer: S ) -> Result<S::Ok, S::Error>where S: Serializer,

Serialize this value into the given Serde serializer.