rust-patch

Patch structs with other structs

rust-patch allows you to avoid boilerplate code when implementing partial updates of Rust structs.
Simply define a patch struct containing a subset of your fields, derive the Patch trait, and specify the original struct using the #[patch] attribute.
Fields of a patch struct may either be of the same type T as in the original struct or Option<T>.
In the latter case, the field to be patched will be left unchanged if the corresponding field in the patch is None

This crate is no_std compatible.

Container attributes

#[patch = "..."]

Set target struct to be patched ```rust use rust_patch::Patch; struct Item { data: u32 }

[derive(Patch)]

[patch = "Item"]

struct ItemPatch { data: Option } ```

Field attributes

By default, any fields in the patch of type Option<T> will be applied as such: rust ignore if let Some(val) = patch.field { target.field = val; } this behavior can be changed by the following field attributes.

#[patch(as_option)]

The as_option attribute allows patching structs where a field itself is already an Option<T> with the following logic: rust ignore if patch.field.is_some() { target.field = patch.field; } Applying this attribute to a field with a type without an is_some() method results in an error.

#[patch(direct)]

The direct attribute makes it so that the field is treated like any other T, meaning it will be applied like this: rust ignore target.field = patch.field; Applying this attribute to a field where the type is not Option<T> is a no-op.

Example

```rust use rust_patch::Patch; use serde::Deserialize;

[derive(PartialEq, Debug)]

struct User { id: String, name: String, email: String, }

[derive(Deserialize, Patch)]

[patch = "User"]

struct UserPatch { name: Option, email: Option, }

let user = User { id: "6bf25b70-bffa-49e0-905b-2d2e608e3abd".tostring(), name: "Max Mustermann".tostring(), email: "max.mustermann@example.org".to_string(), };

let raw_patch = r#"{ "id": "some invalid id", "email": "max.mustermann@example.com" }"#;

let patch: UserPatch = serdejson::fromstr(rawpatch).unwrap(); let patcheduser = patch.apply(user);

// Since id is not part of our UserPatch struct it stays unchanged asserteq! { patcheduser, User { id: "6bf25b70-bffa-49e0-905b-2d2e608e3abd".tostring(), name: "Max Mustermann".tostring(), email: "max.mustermann@example.com".to_string() } }; ```