commit	611edccd16459fd23ffd0bbd182b1dc347019869	[log] [tgz]
author	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Wed May 10 16:18:10 2023 +0000
committer	Android Build Coastguard Worker <android-build-coastguard-worker@google.com>	Wed May 10 16:18:10 2023 +0000
tree	6c7619c9d5f5ac4db66bdfd6285662cca6a59a40
parent	30ad00d11d631c017abd43cbdc6cf32d42f3fb15 [diff]
parent	9e7414541167844ccf1ac976c5b0a7a1575b1ce8 [diff]

tree: 6c7619c9d5f5ac4db66bdfd6285662cca6a59a40

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.