fondant

fondant is a macro based library to take the boilerplate out of configuration handling. Most of fondant is based off the confy crate.

fondant adds a couple of extra features:

• support for json, yaml and toml
• support for custom config paths
• support for custom config file names

Sample usage

// the struct has to derive Serialize, Deserialize and Default
#[derive(Configure, Serialize, Deserialize, Default)]
#[config_file = "config.toml"]
// |
// `-- this attribute sets the file name to "config.toml"
// `-- the file format to "toml"
// `-- the file path to "default" (read the notes below)
struct AppConfig {
    version: u32,
    port: u32,
    username: String,
}

fn main() {
    // use `load` (associated method) to load the config file
    let mut conf = AppConfig::load().unwrap();

    // do stuff with conf
    conf.version = 2;

    // call `store` to save changes
    conf.store().unwrap();
}

Notes:

• load returns Default::default if the config file is not present, and stores a serialized Default::default at the specified path
• the "default" config path varies by platform:
  • GNU/Linux: $XDG_CONFIG_HOME/my_cool_crate/config.toml (follows xdg spec)
  • MacOS: $HOME/Library/Preferences/my_cool_crate/config.toml
  • Windows: {FOLDERID_RoamingAppData}\_project_path_\config

Customization

Set your own filename, for ex.: apprc

#[derive(Configure, Serialize, Deserialize, Default)]
#[config_file = "apprc.toml"]
struct AppConfig {
    // -- snip --
}
// effective path: $XDG_CONFIG_HOME/my_cool_crate/apprc.toml
// effective format: toml

Change file format to yaml, by changing the file extension. Supported extensions are yaml, toml, json:

#[derive(Configure, Serialize, Deserialize, Default)]
#[config_file = "config.yaml"]
struct AppConfig {
    // -- snip --
}
// effective path: $XDG_CONFIG_HOME/my_cool_crate/config.yaml
// effective format: yaml

Override the default config path, for ex.: the home directory (it is not recommended to override config path):

#[derive(Configure, Serialize, Deserialize, Default)]
#[config_file = "~/.apprc.json"]
struct AppConfig {
    // -- snip --
}
// effective path: $HOME/.apprc.json
// effective format: json

Fondant meshes well with Serde, for ex.:

#[derive(Configure, Serialize, Deserialize, Default)]
#[config_file = "config.toml"]
struct Madagascar {
    #[serde(skip)]
    rating: u32,

    name: String,
    penguins: u32,
}

Above snippet produces this config file:

name = 'Central Park Zoo'
penguins = 4

todo

• improve error from trait impl
• use syn::Error and syn::Result to report macro errors
• write docs
• bundle and publish to crates.io