Crate structconf

StructConf is a derive macro to combine argument parsing from clap and config file parsing from rust-ini at compile time. For example:

use clap::App;
use structconf::StructConf;

#[derive(Debug, StructConf)]
struct Config {
    // Option available in the config file and the arguments
    #[conf(help = "description for the argument parser.")]
    pub default: i32,
    // Specify where the options are available.
    #[conf(no_file)]
    pub args_opt: u8,
    #[conf(no_short, no_long)]
    pub conf_opt: Option<String>,
    #[conf(no_short, no_long, no_file)]
    pub ignored: bool,
    // Customize the names
    #[conf(short = "x", long = "renamed_opt", file = "my_opt",
           help = "custom names.")]
    pub renamed: String,
    // Inverse arguments
    #[conf(short = "n", long = "no_pancakes", help = "disable pancakes.")]
    pub pancakes: bool,
    // Custom default values
    #[conf(default = "123.45")]
    pub floating: f64,
}

pub fn main() {
    let app = App::new("demo");
    let conf = Config::parse(app, "config.ini");
    println!("Parsed config: {:#?}", conf);
}

Any named struct that uses #[derive(StructConf)] will have the methods from structconf::StructConf available.

Additional attributes can be added to its fields to customize how they are parsed:

General attributes

• default = "...": a Rust expression that will be evaluated as a fallback value. For example, default = "1+2", or default = "String::from(\"hello\""). Otherwise, the value given by std::default::Default will be used, or in case the assigned type is Option<T>*, None.

* Note: the assigned type must be exactly Option<T> for this to work. std::option::Option<T> won't work, for example.

Argument parser attributes

• help = "...": the help message shown in the argument parser when --help is used.
• long = "arg_name": a custom long argument name. Otherwise, it will be obtained directly from the field's name. do_something will be --do-something.
• no_long: don't include the option as a long argument.
• short = "x": a custom short argument name (only made up of a single character). Otherwise, it will be obtained directly from the field's name. do_something will be -d.
• no_short: don't include the option as a short argument.
• inverse_arg: the argument value is the opposite. The assigned type must implement std::ops::Not. This is useful for arguments where the argument's value is negated:

use structconf::StructConf;

#[derive(StructConf)]
struct Bakery {
    #[conf(inverse_arg, no_short, long = "--no-pancakes")]
    pancakes: bool
}

If both no_long and no_short are provided, the option won't be available in the argument parser at all.

Config file attributes

• file = "...": a custom option name for the config file. Otherwise, it will be the same as the field's name.
• no_file: son't include the option in the config file.
• section: the section in the config file where the option will be. Otherwise, Default is used. For example, #[structconf(section = "Planes")] model_id: i32 will look like this in the config file:

[Planes]
model_id = 123

Enums

Error

Small wrapper for the possible errors that may occur when parsing a StructConf-derived struct.

Traits

StructConf

This trait implements the methods available after using #[derive(StructConf)].

Derive Macros

StructConf