Function deserialize_optional_decimal_from_json 

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

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.