serde_patch/
apply_patch.rs

1use serde::{Serialize, de::DeserializeOwned};
2use serde_json::{Map, Value};
3
4/// Applies a JSON Merge Patch (RFC 7396).
5///
6/// Consumes the current value and returns the updated value.
7///
8/// # Example
9///
10/// ```
11/// #[derive(serde::Serialize, serde::Deserialize, PartialEq, Debug)]
12/// struct User { id: u32, name: String }
13///
14/// let current = User { id: 1, name: "old".to_string() };
15/// let patch = r#"{ "name": "new" }"#;
16///
17/// let updated = serde_patch::apply(current, patch).unwrap();
18/// assert_eq!(updated.name, "new");
19/// assert_eq!(updated.id, 1);
20/// ```
21pub fn apply<T>(current: T, patch_json: &str) -> Result<T, serde_json::Error>
22where
23    T: Serialize + DeserializeOwned,
24{
25    let mut current_val = serde_json::to_value(current)?;
26
27    let patch_val: Value = serde_json::from_str(patch_json)?;
28
29    merge_patch(&mut current_val, &patch_val);
30
31    serde_json::from_value(current_val)
32}
33
34/// Recursively merges a patch into a target JSON value (internal).
35fn merge_patch(target: &mut Value, patch: &Value) {
36    if let Value::Object(patch_map) = patch {
37        if !target.is_object() {
38            *target = Value::Object(Map::new());
39        }
40
41        let target_map = target.as_object_mut().unwrap();
42
43        for (key, patch_value) in patch_map {
44            if patch_value.is_null() {
45                target_map.remove(key);
46            } else {
47                let target_entry = target_map.entry(key.clone()).or_insert(Value::Null);
48                merge_patch(target_entry, patch_value);
49            }
50        }
51    } else {
52        *target = patch.clone();
53    }
54}
serde_patch/apply_patch.rs

serde_patch/
apply_patch.rs
