RECOMMENDATION.md

Recommendation for writing config in your App

Use #[serde(default)] everywhere

This is useful to allow partial config to be deserialized. Without it, you will need to write every fields of a struct to modify only one.

Don't use different default implementation for nested struct.

Take this code as an example:

#[derive(Deserialize, Serialize)]
#[serde(default)]
struct Config {
    nested: NestedConfig,
}

#[derive(Deserialize, Serialize)]
#[serde(default)]
struct NestedConfig {
    number: u32,
}

impl Default for Config {
    fn default() -> Self {
        Self {
            nested: NestedConfig { number: 0 },
        }
    }
}

impl Default for NestedConfig {
    fn default() -> Self {
        Self { number: 1 }
    }
}

With the value {}, number will be equal to 0, while with the value { "nested": {} }, it will be equal to 1.

Always use a String for Keys of Maps.

This include HashMap, BTreeMap, etc ... It is firstly because JSON schema, figment, and other config formats like kdl or json doesn't support it (ron does tho). This make sense when thinking about it, because for managing perfectly a Map independently of the App code, we need to know the exact implementation of the key comparison.