3 unstable releases
0.2.1 | Oct 19, 2023 |
---|---|
0.2.0 | Oct 14, 2022 |
0.1.0 | Oct 13, 2022 |
#287 in Configuration
4,013 downloads per month
Used in 2 crates
16KB
Clap and Serde derive
With the ClapSerde
procedural macro both clap and serde can be derived from a struct.
Then the struct can be parsed from clap and serde sources as in a layered config: the last
source has the precedence.
Args::from(serde_parsed)
.merge_clap();
In the snippet the precedence is:
- Command line from clap;
- Config file from serde;
- Default values.
Example
In this example we define a struct which derives both clap and serde. The struct has various parameter type and also various attributes on its fields.
Finally we parse the structure from a YAML file with serde and then from command line with clap. The arguments from clap will override those from serde; the default value will be used if no source contained the field.
use clap_serde_derive::{
clap::{self, ArgAction},
serde::Serialize,
ClapSerde,
};
#[derive(ClapSerde, Serialize)]
#[derive(Debug)]
#[command(author, version, about)]
pub struct Args {
/// Input files
pub input: Vec<std::path::PathBuf>,
/// String argument
#[arg(short, long)]
name: String,
/// Skip serde deserialize
#[default(13)]
#[serde(skip_deserializing)]
#[arg(long = "num")]
pub clap_num: u32,
/// Skip clap
#[serde(rename = "number")]
#[arg(skip)]
pub serde_num: u32,
/// Recursive fields
#[clap_serde]
#[command(flatten)]
pub suboptions: SubConfig,
}
#[derive(ClapSerde, Serialize)]
#[derive(Debug)]
pub struct SubConfig {
#[default(true)]
#[arg(long = "no-flag", action = ArgAction::SetFalse)]
pub flag: bool,
}
let args = Args::from(serde_yaml::from_str::<<Args as ClapSerde>::Opt>("number: 12").unwrap())
.merge_clap();
assert_eq!(
serde_yaml::to_string(&args).unwrap(),
serde_yaml::to_string(&Args {
serde_num: 12,
clap_num: 13,
..Args::default()
})
.unwrap(),
);
Config path from command line
You can easily take the config file path from command line in this way.
use std::{fs::File, io::BufReader};
use clap_serde_derive::{
clap::{self, Parser},
ClapSerde,
};
#[derive(Parser)]
#[command(author, version, about)]
struct Args {
/// Input files
input: Vec<std::path::PathBuf>,
/// Config file
#[arg(short, long = "config", default_value = "config.yml")]
config_path: std::path::PathBuf,
/// Rest of arguments
#[command(flatten)]
pub config: <Config as ClapSerde>::Opt,
}
#[derive(ClapSerde)]
struct Config {
/// String argument
#[arg(short, long)]
name: String,
}
// Parse whole args with clap
let mut args = Args::parse();
// Get config file
let config = if let Ok(f) = File::open(&args.config_path) {
// Parse config with serde
match serde_yaml::from_reader::<_, <Config as ClapSerde>::Opt>(BufReader::new(f)) {
// merge config already parsed from clap
Ok(config) => Config::from(config).merge(&mut args.config),
Err(err) => panic!("Error in configuration file:\n{}", err),
}
} else {
// If there is not config file return only config parsed from clap
Config::from(&mut args.config)
};
Dependencies
~1.2–2MB
~37K SLoC