yanganto / struct-patch

A lib help you patch Rust instance, and easy to partial update configures.

Struct Patch

A lib help you patch Rust instance, and easy to partial update configures.

Introduction

This crate provides the Patch trait and an accompanying derive macro.

Deriving Patch on a struct will generate a struct similar to the original one, but with all fields wrapped in an Option.
An instance of such a patch struct can be applied onto the original struct, replacing values only if they are set to Some, leaving them unchanged otherwise.

Quick Example

use struct_patch::Patch;
use serde::{Deserialize, Serialize};

#[derive(Default, Debug, PartialEq, Patch)]
#[patch(attribute(derive(Debug, Default, Deserialize, Serialize)))]
struct Item {
    field_bool: bool,
    field_int: usize,
    field_string: String,
}

fn patch_json() {
    let mut item = Item {
        field_bool: true,
        field_int: 42,
        field_string: String::from("hello"),
    };

    let data = r#"{
        "field_int": 7
    }"#;

    let patch: ItemPatch = serde_json::from_str(data).unwrap();

    item.apply(patch);

    assert_eq!(
        item,
        Item {
            field_bool: true,
            field_int: 7,
            field_string: String::from("hello")
        }
    );
}

Documentation and Examples

Also, you can modify the patch structure by defining #[patch(...)] attributes on the original struct or fields.

Struct attributes:

• #[patch(name = "...")]: change the name of the generated patch struct.
• #[patch(attribute(...))]: add attributes to the generated patch struct.
• #[patch(attribute(derive(...)))]: add derives to the generated patch struct.

Field attributes:

• #[patch(skip)]: skip the field in the generated patch struct.
• #[patch(name = "...")]: change the type of the field in the generated patch struct.
• #[patch(attribute(...))]: add attributes to the field in the generated patch struct.
• #[patch(attribute(derive(...)))]: add derives to the field in the generated patch struct.

Please check the traits of document to learn more.

The examples demo following scenarios.

• diff two instance for a patch
• create a patch from json string
• rename the patch structure
• check a patch is empty or not
• add attribute to patch struct