I am creating a configuration parser and I am using the toml crate to parse the config file (which is in toml) to a string. I want to create certain checks to ensure the user does not include fields not supported or not included in the config struct. This is what the config struct looks like

#[derive(Deserialize, Debug)]
pub struct Config {
    add: Option<Add>,
    sub: Option<Sub>,
    mul: Option<Mul>,
}

And the add, sub and mul structs look something like this

#[derive(Deserialize, Debug, Clone, PartialEq)]
pub struct add {
    width: u32,
    granularity: Option<u32>,
}

Since all the 3 structs within Config struct are optional, how do I create a vector of Some structs if they happen to be specified in the toml configuration?

For further context – here is an example config file

[add]
width = 16

[sub]
width = 32

[mul]
width = 32
granularity = 2

Would a schema check on the toml config be a better solution than trying to check for valid entries in the configuration file? Please drop some suggestions, thanks!

I tried to create a function for the Config struct to return a vector of structs if they are specified, but I do not know how to do this for arbitrary entries (i.e. without explicitly checking each sub-struct of Config struct).