Function deserialize_default_from_null

pub fn deserialize_default_from_null<'de, D, T>(
    deserializer: D,
) -> Result<T, D::Error>
where
    D: Deserializer<'de>,
    T: Deserialize<'de> + Default,

Deserializes default value from nullable value. If the original value is null, Default::default() is used.

Example:

use serde_aux::prelude::*;

#[derive(serde::Serialize, serde::Deserialize, Debug)]
struct MyStruct {
    #[serde(deserialize_with = "deserialize_default_from_null")]
    null_as_default: u64,
}

let s = r#" { "null_as_default": 42 } "#;
let a: MyStruct = serde_json::from_str(s).unwrap();
assert_eq!(a.null_as_default, 42);

let s = r#" { "null_as_default": null } "#;
let a: MyStruct = serde_json::from_str(s).unwrap();
assert_eq!(a.null_as_default, 0);

let s = r#" { "null_as_default": "wrong_type" } "#;
assert!(serde_json::from_str::<MyStruct>(s).is_err());