Clap and Serde derive

With the [clap_serde] 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.

rust ignore Args::from(serde_parsed) .merge_clap();

In the snippet the precedence is:

1. Command line from clap;
2. Config file from serde;
3. 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.

```rust use clapserdederive::{ clap::{self, ArgAction}, clap_serde, ClapSerde, };

[clap_serde]

[derive(Debug)]

[clap(author, version, about)]

pub struct Args { /// Input files pub input: Vec,

/// String argument
#[clap(short, long)]
name: String,

/// Skip serde deserialize
#[default(13)]
#[serde(skip_deserializing)]
#[clap(long = "num")]
pub clap_num: u32,

/// Skip clap
#[serde(rename = "number")]
#[clap(skip)]
pub serde_num: u32,

/// Recursive fields
#[clap_serde]
#[clap(flatten)]
pub suboptions: SubConfig,

}

[clap_serde]

[derive(Debug)]

pub struct SubConfig { #[default(true)] #[clap(long = "no-flag", action = ArgAction::SetFalse)] pub flag: bool, }

let args = Args::from(serdeyaml::fromstr::<::Opt>("number: 12").unwrap()) .mergeclap(); asserteq!( serdeyaml::tostring(&args).unwrap(), serdeyaml::tostring(&Args { serdenum: 12, clapnum: 13, ..Args::default() }) .unwrap(), ); ```

Config path from command line

You can easily take the config file path from command line in this way.

```rust use std::{fs::File, io::BufReader};

use clapserdederive::{ clap::{self, ArgAction, Parser}, clap_serde, ClapSerde, };

[derive(Parser)]

[clap(author, version, about)]

struct Args { /// Input files input: Vec,

/// Config file
#[clap(short, long = "config", default_value = "config.yml")]
config_path: std::path::PathBuf,

/// Rest of arguments
#[clap(flatten)]
pub config: <Config as ClapSerde>::Opt,

}

[clap_serde]

struct Config { /// String argument #[clap(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.configpath) { // Parse config with serde match serdeyaml::from_reader::<_, ::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) }; ```