Twelf
Twelf is a configuration solution for Rust including 12-Factor support. It is designed with
Layer
s in order to configure different sources and formats to build your configuration. The main goal is to be very simple using the proc macrotwelf::config
.
For now it supports :
- Default settings (inside your codebase with
#[serde(default = ...)]
coming from serde) - Reading from
TOML
,YAML
,JSON
,DHALL
,INI
files - Reading from environment variables: it supports
HashMap
structure withMY_VARIABLE="mykey=myvalue,mykey2=myvalue2"
and also array likeMY_VARIABLE=first,second
thanks to envy. - All serde attributes can be used in your struct to customize your configuration as you wish
- Reading your configuration from your command line built with clap
Usage
Simple with JSON and environment variables
use twelf::{config, Layer};
#[config]
struct Conf {
test: String,
another: usize,
}
// Init configuration with layers, each layers override only existing fields
let config = Conf::with_layers(&[
Layer::Json("conf.json".into()),
Layer::Env(Some("PREFIX_".to_string()))
]).unwrap();
Example with clap support
use twelf::{config, Layer};
#[config]
struct Conf {
/// Here is an example of documentation which is displayed in clap
test: String,
another: usize,
}
// Will generate global arguments for each of your fields inside your configuration struct
let app = clap::App::new("test").args(&Conf::clap_args());
// Init configuration with layers, each layers override only existing fields
let config = Conf::with_layers(&[
Layer::Json("conf.json".into()),
Layer::Env(Some("PREFIX_".to_string())),
Layer::Clap(app.get_matches().clone())
]).unwrap();
// ... your application code
Check here for more examples.
TODO:
- Better error report with explicit layer name
- Suggest crates like https://github.com/jonasbb/serde_with and add usecases
- Support Vault
- Implement a trait/api to extend and let users fetch config from remote
- Refactor to let user extend layers
- Add support of nested struct in envy
- Fix issue with
#[serde(flatten)] when you use other type than
String` in sub types
Alternatives
- config-rs is almost doing the same except the environment layer (for example we support hashmap and array in environment variables). Also
config-rs
don't have clap support and it didn't use any proc-macros if you're not very fan of proc-macros.