Function deserialize_optional_json 

pub fn deserialize_optional_json<'de, D: Deserializer<'de>>(
    deserializer: D,
) -> Result<Option<Decimal>, D::Error>

Deserializes an optional exact JSON decimal, accepting null as None.

Add #[serde(default)] to accept a missing field. Other values follow deserialize_json.

Errors

Returns an error if deserialize_json rejects a non-null value.