Crate clap_adapters 

Adapter types for declaratively loading configurations via clap

Types which implement FromStr may be used in a clap derive struct. This crate provides adapters which accept Path-like inputs as arguments from the user and automatically loads and parses the file at the path.

The base adapter is PathTo<T>, which takes a path from the user and attempts to load the contents of the file into an instance of T, which must implement FromReader. This crate implements FromReader for the following types:

• Vec<u8>
• String
• JsonOf<T> (where T: serde::DeserializeOwned)
• TomlOf<T> (where T: serde::DeserializeOwned)
• YamlOf<T> (where T: serde::DeserializeOwned)

Additionally, PathTo may be wrapped in either Periodic<T> or Reloading<T> to gain the ability to automatically reload the file at the user-given path at a regular interval or when the file is updated, respectively.

Example

use clap::Parser;
use clap_adapters::prelude::*;

#[derive(Debug, Parser)]
struct Cli {
    /// Path to a config file of arbitrary Json
    #[clap(long)]
    config: PathTo<JsonOf<serde_json::Value>>,
}

// Create a config file in a temporary directory
let config_dir = tempfile::tempdir()?;
let config_path = config_dir.path().join("config.json");
let config_path_string = config_path.display().to_string();

// Write a test config of {"hello":"world"} to the config file
let config = serde_json::json!({"hello": "world"});
let config_string = serde_json::to_string(&config)?;
std::fs::write(&config_path, &config_string)?;

// Parse our CLI, passing our config file path to --config
let cli = Cli::parse_from(["app", "--config", &config_path_string]);
let data = cli.config.data();

// We should expect the value we get to match what we wrote to the config
assert_eq!(data, &serde_json::json!({"hello":"world"}));

Modules

prelude

Convenience import for clap adapter building blocks

traits

Traits for glueing adapters together

Structs

JsonOf

An adapter for deserializing a Json document from a buffered reader

PathTo

An adapter for automatically loading the contents of a file path

Periodic

Given a Path from the user, provides a utility that reloads the file at the path at a fixed interval

Reloading

Given a Path from the user, provides a utility that reloads the file at the path whenever the file is updated

TomlOf

An adapter for deserializing a Toml document from a buffered reader

YamlOf

An adapter for deserializing a Yaml document from a buffered reader