commit	344d03e9df9fce21b0797a4ca1c811aa154b5f68	[log] [tgz]
author	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Tue Oct 08 23:11:31 2024 +0000
committer	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Tue Oct 08 23:11:31 2024 +0000
tree	2d2a31d3862a058bcc58a6a47b8d3543f2b96edf
parent	b48143cf8bb93e91316f74a373651845090cddc7 [diff]
parent	a141253c5e5c26729f21119163f925aa2bf50cec [diff]

tree: 2d2a31d3862a058bcc58a6a47b8d3543f2b96edf

README.md

merge-rs

The merge crate provides the Merge trait that can be used to merge multiple values into one:

trait Merge {
    fn merge(&mut self, other: Self);
}

Merge is implemented for Option and can be derived for structs:

use merge::Merge;

#[derive(Merge)]
struct User {
    // Fields with the skip attribute are skipped by Merge
    #[merge(skip)]
    pub name: &'static str,

    // The Merge implementation for Option replaces its value if it is None
    pub location: Option<&'static str>,

    // The strategy attribute is used to customize the merge behavior
    #[merge(strategy = merge::vec::append)]
    pub groups: Vec<&'static str>,
}

let defaults = User {
    name: "",
    location: Some("Internet"),
    groups: vec!["rust"],
};
let mut ferris = User {
    name: "Ferris",
    location: None,
    groups: vec!["mascot"],
};
ferris.merge(defaults);

assert_eq!("Ferris", ferris.name);
assert_eq!(Some("Internet"), ferris.location);
assert_eq!(vec!["mascot", "rust"], ferris.groups);

A merge strategy is a function with the signature fn merge<T>(left: &mut T, right: T) that merges right into left. The merge crate provides strategies for the most common types, but you can also define your own strategies.

The trait can be used to merge configuration from different sources, for example environment variables, multiple configuration files and command-line arguments, see the args.rs example.

Features

This crate has the following features:

derive (default): Enables the derive macro for the Merge trait using the merge_derive crate.
num (default): Enables the merge strategies in the num module that require the num_traits crate.
std (default): Enables the merge strategies in the vec module that require the standard library. If this feature is not set, merge is a no_std library.

Minimum Supported Rust Version

This crate supports Rust 1.36.0 or later.

Contact

For bug reports, patches, feature requests and other messages, please send a mail to ~ireas/public-inbox@lists.sr.ht using the [merge-rs] prefix in the subject.

License

This project is dual-licensed under the Apache-2.0 and MIT licenses. The documentation and configuration files contained in this repository are licensed under the Creative Commons Zero license. You can find a copy of the license texts in the LICENSES directory.

merge-rs complies with version 3.0 of the REUSE specification.