configured

Opinionated utility, built on top of the config crate, to load a configuration from well defined layers into any type which can be deserialized by Serde using the case chosen by the caller (e.g. Case::Kebab or Case::Snake).

First, values from the mandatory default configuration file at <CONFIG_DIR>/default.yaml/toml are loaded.

Then, if the environment variable CONFIG_OVERLAYS is defined, its comma separated overlays (e.g. "prod" or "feat, dev") at <CONFIG_DIR>/<overlay>.yaml/toml are loaded from left to right as overlays, i.e. adding or overwriting already existing values.

Finally environment variables prefixed with <CONFIG_ENV_PREFIX>__ (the prefix defaults to CFG) and segments separated by __ (double underscores are used as segment separators to allow for single underscores in segment names) are used as final overlay. Each segment is converted to the Case passed to load, so it matches the #[serde(rename_all = ...)] of the target type.

File formats are gated behind features: yaml (default) and toml.

Example

use configured::{ Case, Configured };
use serde::Deserialize;

#[derive(Debug, Deserialize)]
struct Config {
    contact: Contact,
    address: Address,
}

#[derive(Debug, Deserialize)]
struct Contact {
    first_name: String,
    last_name: String,
}

#[derive(Debug, Deserialize)]
struct Address {
    street_name: String,
    zip_code: String,
}

let config = Config::load(Case::Snake)?;

License

This code is open source software licensed under the Apache 2.0 License.