rust merge multiple yaml docs

merge_yaml.rs

// See https://stackoverflow.com/questions/67727239/how-to-combine-including-nested-array-values-two-serde-yamlvalue-objects
// Note this is not https://docs.rs/serde_yaml/latest/serde_yaml/value/enum.Value.html#method.apply_merge

use serde::{Serialize, Deserialize};
use serde_yaml::Value;

fn merge_yaml(a: &mut serde_yaml::Value, b: serde_yaml::Value) {
    match (a, b) {
        (a @ &mut serde_yaml::Value::Mapping(_), serde_yaml::Value::Mapping(b)) => {
            let a = a.as_mapping_mut().unwrap();
            for (k, v) in b {
                /*if v.is_sequence() && a.contains_key(&k) && a[&k].is_sequence() { 
                    let mut _b = a.get(&k).unwrap().as_sequence().unwrap().to_owned();
                    _b.append(&mut v.as_sequence().unwrap().to_owned());
                    a[&k] = serde_yaml::Value::from(_b);
                    continue;
                }*/
                if !a.contains_key(&k) {a.insert(k.to_owned(), v.to_owned());}
                else { merge_yaml(&mut a[&k], v); }

            }
            
        }
        (_, Value::Null) => {}
        (a, b) => *a = b,
    }
}

fn main() -> Result<(), serde_yaml::Error> {

    let s_a = "x: 1.0\ny_z:\n  r: 2.0\n";
    let s_b = "y_z:\n  alpha: 45.0";
    

    let mut yaml_a: Value = serde_yaml::from_str(&s_a)?;
    let yaml_b: Value = serde_yaml::from_str(&s_b)?;
    
    merge_yaml(&mut yaml_a, yaml_b);
    
    #[derive(Serialize, Deserialize, PartialEq, Debug)]
    struct Point {
        x: f32,
        y_z: Radial,
    }
    
    #[derive(Serialize, Deserialize, PartialEq, Debug)]
    struct Radial {
        r: f32,
        alpha: f32,
    }
    
    println!("{yaml_a:?}");
    
    let p: Point = serde_yaml::from_value(yaml_a).unwrap();
    println!("{p:?}");
    
    Ok(())
}