use serde_json::Value;
pub fn merge(a: &mut Value, b: Value) {
match (a, b) {
(a @ &mut Value::Object(_), Value::Object(b)) => {
let a = a.as_object_mut().unwrap();
for (k, v) in b {
merge(a.entry(k).or_insert(Value::Null), v);
}
}
(a, b) => *a = b,
}
}