How to add a value at a path?

[gkorland]

e.g.

{ 
   "a" : {
       "b": 1
   }
}

Add $.a.c=2
to:

{ 
   "a" : { 
       "b": 1,
       "c": 2
   }
}

[freestrings]

if a value exist in a given path as above, you can use the replace_with function.

fn add(
    json: serde_json::Value,
    path: &str,
    key: &str,
    value: serde_json::Value,
) -> Result<Option<serde_json::Value>, jsonpath::JsonPathError> {
    let mut wrap = Box::new(value);
    let mut selector = jsonpath::SelectorMut::new();
    let ret = selector
        .value(json)
        .str_path(path)?
        .replace_with(&mut |found| {
            let mut ret = found.clone();
            if let serde_json::Value::Object(ref mut map) = ret {
                map.insert(key.to_string(), wrap.take());
            }
            ret
        })?
        .take();
    Ok(ret)
}

fn main() -> Result<(), jsonpath::JsonPathError> {
    let ret = add(
        json!(
            {
                "a" : {
                    "b" : 1
                }
            }
        ),
        "$.a",
        "c",
        json!(2),
    )?;

    println!("{:?}", ret);
    Ok(())
}

[gkorland]

The thing is that we're getting a string path from the user and it's hard to remove the last part of the path so we can find the right place to add the new node.

e.g. in this simple example we'll get $.a.c from the user and will have to do parse the path and remove the last .c