#config #yaml #toml #json #dotenv


Viperus is an (in)complete configuration solution for rust applications heavly inspired by the GO package Viper.It supports defaults reading from JSON, TOML, YAML, envfile,java properties, environment variables reading from Clap command line flags setting explicit values

9 releases

✓ Uses Rust 2018 edition

new 0.1.10 Jan 19, 2020
0.1.9 Jan 18, 2020

#12 in Configuration

Download history 39/week @ 2020-01-02 99/week @ 2020-01-09 106/week @ 2020-01-16

52 downloads per month



viperus Build Status Coverage Status

̶g̶o̶ rust configuration with fangs!

viperus is an (in)complete configuration solution for Rust applications. inspired heavly inspired by the wonderful go package https://github.com/spf13/viper use at your own risk. ;-)

no Go projects h̶a̶s̶ ̶b̶e̶e̶n̶ ̶h̶a̶r̶m̶e̶d̶ are built using Viperus :-)

Recent Changes

  • 0.1.10 adapters load cfg data from std:io::Read
  • 0.1.9 optional automatic prefixed environment variable mapping,basic error propagation, cleaned dependency
  • 0.1.8 add cache feature, modular "featurization"
  • 0.1.5 add watch_all files with autoreload
  • 0.1.4 add format : java properties files
  • 0.1.3 better clap args : default values
  • 0.1.2 relaod config from files
  • 0.1.1 fixes dcs
  • 0.1.0 first release

What is Viperus?

a package that handles some types of configuration modes with differente formats,cli params and environment . It supports:

  • setting defaults
  • reading from JSON, TOML, YAML, dotenv file ,java properties config files
  • reading from environment variables
  • reading from Clap command line flags
  • setting explicit values
  • reload of all files
  • whatch config files and reolad all in something changes
  • caching

Why Viperus?

beacuse I was migrating some go apps... and a was missing Viper ease of use :-)

Viperus uses the following decreasing precedence order.

  • explicit call to add
  • clap flag
  • config
  • environment variables
  • default

Viperus merge configuration from toml,dotenv,json,yaml files and clap options in sigle typed hash structure. with defaults, and type checking

you can create a stand alone Viperus object or "enjoy" a global instance ( thread safe protected with a mutex) via shadow functions load_file|get|add|load_clap that are routed to the static instance.

//add a dotenv config file , keys defautls di env variables
viperus::load_file(".env", viperus::Format::ENV).unwrap();
//add another file
viperus::load_file("user.env", viperus::Format::ENV).unwrap();

//automatically map env variable staring with "TEST_" to config keys

//watch the config and autoreload if something changes
//enable caching  -- file reload invalidates cache
// cache i thread safe for the global "static" instance
let ok=viperus::get::<bool>("TEST_BOOL").unwrap();

by the way , Yes I konw globals are evil. but as I was inspired by the go package viper.... if you dislike globals you can opt-out disabling in your cargo.toml the feature "global".


you can enable caching for a x4 speed-up. cache is thread safe only when used with the global instance taht is behing a arc mutex


reloading files with an excplicit viperus::reload() , or for effect of a file change when file watch is active invalidates the cache.


the crate uses log facade , and test the env_logger you can set the env variable to RUST_LOG=viperus=[DEBUG LEVEL] with [DEBUG LEVEL] = info|warning|debug or RUST_LOG=[DEBUG LEVEL]


the crate in "featurized" with the features enabled by default

  • feature = "fmt-[format]" with [format] in 'json,end,toml,yaml,javaproperties,clap' enabling the relative format
  • feature ="global" enabling the global tread safe configuration
  • feature ="watch" enabling the automatic file reload wirh prerequisite feature=global
  • feature ="cache" aneglig caching

single featues could be activated in a selective way via cargo.toml

version = "0.1.8"
# do not include the default features, and optionally
default-features = false 
# cherry-pick individual features
features = ["global", "cache","watch","fmt-yaml"]


you can find some integration tests in the test dir and also in the example folder you can run example with cargo:

cargo run --example cli-clap-yaml -- 
cargo run --example cli-clap-yaml -- -u http://nowhere/api/v1

the first run print the value from the example.yaml file the second from the cli arg

let matches = App::new("My Super Program")
                 .help("Sets the level of verbosity"))
let mut v = Viperus::new();

//enable clap
//enable a yaml json toml file
v.load_file(&path!(".","assets","test.yaml"), Format::YAML).unwrap();
v.load_file(&path!(".","assets","test.json"), Format::JSON).unwrap();
v.load_file(&path!(".","assets","test.toml"), Format::TOML).unwrap();
v.load_file(&path!(".","assets","test.properties"), Format::JAVAPROPERTIES).unwrap();
//link the "v" clap option to the key "verbose"

//add an explicit overload 
v.add("service.url", String::from("http://example.com"));
debug!("final {:?}", v);

//get a typed key
let s: &str = v.get("service.url").unwrap();
assert_eq!("http://example.com", s);

//get a bool from configs or app args
let fVerbose=v.get::<bool>("verbose").unwrap();
assert_eq!(true, fVerbose);


  • remote configs
  • better error propagation
  • stabilize api
  • improve documentation and examples
  • improve my rust karma


~31K SLoC