Failing to deserialize skipped default None variant for content generated by rmp_serde::to_vec

[jsprog]

To trigger this issue, you need to create a struct containing at least two fields:

• the first field is optional with the default value of None, and the created instance contains the None variant for this field.
• the optional field is not the last one in the structure.
• try to deserialize some content serialized with rmp::to_vec (not rmp::to_vec_named).

use serde::{Serialize, Deserialize};

fn main() {
    let record = Record::default();
    println!("{:?}", record);

    let encoded = rmp_serde::to_vec(&record).unwrap(); // this will fail later with decoding
    // let encoded = rmp_serde::to_vec_named(&record).unwrap(); // note: this won't fail with decoding
    println!("{:?}", encoded);

    let decoded: Record = rmp_serde::from_slice(&encoded).unwrap();
    println!("{:?}", decoded);
}


#[derive(Serialize, Deserialize, Debug)]
struct Record {
    #[serde(default)]
    #[serde(skip_serializing_if = "Option::is_none")]
    optional_field: Option<u8>, // note: this isn't the last field

    another_field: u8, // note: you need to place this after 'optional_field' to trigger this issue
}
impl Default for Record {
    fn default() -> Self {
        Self {
            optional_field: None, // note: replacing with Some(value) won't trigger this issue
            another_field: 10,
        }
    }
}

Testing Platform:

• Linux Mint 20.2 (x86-64)
• cargo 1.58.0
• rustc 1.58.1
• serde = "1.0.136"
• rmp-serde = "1.0.0"