admerge but ignore None values in the incoming data

[beeb]

I have a clap item which looks like so:

#[derive(clap::Parser, Serialize, Deserialize)]
#[serde_with::skip_serializing_none]
#[command(version, about)]
pub struct Args {
    #[arg(long, num_args = 0..=1, default_missing_value = "true")]
    pub flag: Option<bool>,
}

This means the flag is None if the user doesn't provide it to the CLI, and is Some(true) if user provides --flag and is Some(false) if user provides --flag=false.

The idea is that I want None to mean a default value of true.

Now I have my final config object:

#[derive(Serialize, Deserialize)]
pub struct Config {
    pub flag: bool,
}

impl From<Args> for Config {
    fn from(value: Args) -> Self {
        Self {
            flag: value.flag.unwrap_or(true)
        }
    }
}

Now I want to merge a Toml provider with this Serialize provider, with the CLI options taking precedence (I use admerge because I also have Vecs in my data which should be merged):

let temp: Args = Figment::new().admerge(Toml::file("myfile.toml")).admerge(Serialized::defaults(Args::parse())).extract()?;
let config: Config = temp.into();

My problem

The problem is that if I set in my TOML flag = false and then provide no flag to the CLI, I would want the final value to be Some(false), but admerge updates the value for flag to be None even if the Toml said false. This means my final Config value is true because that's the default for None.

Is there a way to merge the CLI struct but no overwrite the previous value (from toml) if it's None?