Settings

Settings are the individual fields of a Config struct or variants of a Config enum, and can be annotated with the optional #[setting] attribute.

Attribute fields

The following fields are supported for the #[setting] field/variant attribute:

• default - Sets the default value.
• env (struct only) - Sets the environment variable to receive a value from.
• extend (struct only) - Enables a configuration to extend other configs.
• merge - Defines a function to use for merging values.
• nested - Marks the field as using a nested Config.
• parse_env (struct only) - Parses the environment variable value using a function.
• required - Marks the field as required. This is useful for Option types that do not support Default, but require a value.
• validate - Defines a function to use for validating values.

And the following for serde compatibility:

• alias
• flatten
• rename
• skip
• skip_deserializing
• skip_serializing

Serde support

A handful of serde attribute fields are currently supported (above) and will apply a #[serde] attribute to the partial implementation.

#![allow(unused)]
fn main() {
#[derive(Config)]
struct Example {
	#[setting(rename = "type")]
	pub type_of: SomeEnum,
}
}

These values can also be applied using #[serde], which is useful if you want to apply them to the main struct as well, and not just the partial struct.