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//! 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.
//!
//! The following code shows how `struct-patch` can be used together with `serde` to patch structs with JSON objects.
//! ```rust
//! use struct_patch::Patch;
//! use serde::{Deserialize, Serialize};
//!
//! #[derive(Default, Debug, PartialEq, Patch)]
//! #[patch_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")
//! }
//! );
//! }
//! ```
//!
//! More details on how to use the the derive macro, including what attributes are available, are available under [`Patch`]
#![cfg_attr(not(test), no_std)]
#[doc(hidden)]
pub use struct_patch_derive::Patch;
pub mod traits;
pub use traits::*;
#[cfg(test)]
mod tests {
use serde::Deserialize;
use struct_patch::Patch;
#[cfg(feature = "status")]
use struct_patch::PatchStatus;
use crate as struct_patch;
#[test]
fn test_basic() {
#[derive(Patch, Debug, PartialEq)]
struct Item {
field: u32,
other: String,
}
let mut item = Item {
field: 1,
other: String::from("hello"),
};
let patch = ItemPatch {
field: None,
other: Some(String::from("bye")),
};
item.apply(patch);
assert_eq!(
item,
Item {
field: 1,
other: String::from("bye")
}
);
}
#[test]
#[cfg(feature = "status")]
fn test_empty() {
#[derive(Patch)]
#[patch_derive(Debug, PartialEq)]
struct Item {
data: u32,
}
let patch = ItemPatch { data: None };
let other_patch = Item::new_empty_patch();
assert!(patch.is_empty());
assert_eq!(patch, other_patch);
let patch = ItemPatch { data: Some(0) };
assert!(!patch.is_empty());
}
#[test]
fn test_derive() {
#[derive(Patch)]
#[patch_derive(Copy, Clone, PartialEq, Debug)]
struct Item;
let patch = ItemPatch {};
let other_patch = patch;
assert_eq!(patch, other_patch);
}
#[test]
fn test_name() {
#[derive(Patch)]
#[patch_name = "PatchItem"]
struct Item;
let patch = PatchItem {};
let mut item = Item;
item.apply(patch);
}
#[test]
fn test_skip() {
#[derive(Patch, PartialEq, Debug)]
#[patch_derive(PartialEq, Debug, Deserialize)]
struct Item {
#[patch_skip]
id: u32,
data: u32,
}
let mut item = Item { id: 1, data: 2 };
let data = r#"{ "id": 10, "data": 15 }"#; // Note: serde ignores unknown fields by default.
let patch: ItemPatch = serde_json::from_str(data).unwrap();
assert_eq!(patch, ItemPatch { data: Some(15) });
item.apply(patch);
assert_eq!(item, Item { id: 1, data: 15 });
}
#[test]
fn test_nested() {
#[derive(PartialEq, Debug, Patch, Deserialize)]
#[patch_derive(PartialEq, Debug, Deserialize)]
struct B {
c: u32,
d: u32,
}
#[derive(PartialEq, Debug, Patch, Deserialize)]
#[patch_derive(PartialEq, Debug, Deserialize)]
struct A {
#[patch_name = "BPatch"]
b: B,
}
let mut a = A {
b: B { c: 0, d: 0 },
};
let data = r#"{ "b": { "c": 1 } }"#;
let patch: APatch = serde_json::from_str(data).unwrap();
// assert_eq!(
// patch,
// APatch {
// b: Some(B { id: 1 })
// }
// );
a.apply(patch);
assert_eq!(
a,
A {
b: B { c: 1, d: 0 }
}
);
}
}