Crate salak

A layered configuration loader with zero-boilerplate configuration management.

About

salak is a rust version of layered configuration loader inspired by spring-boot. salak also has a haskell version.

salak defines following default PropertySources:

1. Command line arguments using clap to parsing -P, --propery KEY=VALUE.
2. System Environment.
3. app.toml(*) in current dir and $HOME dir. Or if you specify APP_CONF_DIR dir, then only load toml in this dir.

* APP_CONF_NAME can be specified to replace app.

Placeholder format

1. ${key:default} means get value of key, if not exists then return default.
2. ${key} means get value of key, if not exists then return PropertyError::NotFound(_).
3. \$\{key\} means escape to ${key} or u can use disable_placeholder attribute.

Key format

1. a.b.c is a normal key separated by dot(.).
2. a.b[0], a.b[1], a.b[2]... is a group of keys with arrays.
3. System environment key will be changed from HELLO_WORLD <=> hello.world, HELLO__WORLD_HOW <=> hello_world.how, hello[1].world => HELLO_1_WORLD <=> hello.1.world.

Auto derived parameters.

attribute default to set default value.

1. #[salak(default="string")]
2. #[salak(default=1)]

attribute disable_placeholder to disable placeholder parsing.

1. #[salak(disable_placeholder)]
2. #[salak(disable_placeholder = true)]

Features

Default features

1. enable_log, enable log record if enabled.
2. enable_toml, enable toml support.
3. enable_derive, enable auto derive FromEnvironment for struts.

Optional features

1. enable_clap, enable default command line arguments parsing by clap.
2. enable_yaml, enable yaml support.

Quick Example

use salak::*;
#[derive(FromEnvironment, Debug)]
pub struct DatabaseConfig {
    url: String,
    #[salak(default = "salak")]
    name: String,
    #[salak(default = "{database.name}")]
    username: String,
    password: Option<String>,
    #[salak(default = "${Hello}", disable_placeholder)]
    description: String,
}

fn main() {
  std::env::set_var("database.url", "localhost:5432");
  let env = SalakBuilder::new()
     .with_default_args(auto_read_sys_args_param!()) // This line need enable feature `enable_clap`.
     .build();
  
  match env.require::<DatabaseConfig>("database") {
      Ok(val) => println!("{:?}", val),
      Err(e) => println!("{}", e),
  }
}
// Output: DatabaseConfig {
//  url: "localhost:5432",
//  name: "salak",
//  username: "salak",
//  password: None,
//  description: "${Hello}"
// }

Modules

args	Provide command line arguments PropertySource.
env	Provide system environment PropertySource.
map	Provide hashmap PropertySource.
property	Property converter.
toml	enable_toml Provide toml PropertySource.
yaml	enable_yaml Provide yaml PropertySource.

Macros

auto_read_sys_args_param

enable_clap Auto generate SysArgsParam from Cargo.toml.

Structs

EnvironmentOption	An option be used to add default values for some keys.
PlaceholderResolver	An implementation of Environment that can resolve placeholder for values.
Salak	A wrapper for Environment, which can hide the implementation details.
SalakBuilder	Salak builder.
SourceRegistry	An implementation of Environment for registering PropertySource.

Enums

Property	Unified property structure.
PropertyError	Property Error

Traits

Environment	An environment for getting properties in multiple PropertySources.
FromEnvironment	Generate object from Environment.
PropertySource	An abstract source loader from various sources, such as commandline arguments, system environment, files, etc.

Derive Macros

FromEnvironment

enable_derive Auto derive FromEnvironment for struct.