# 🧱 Lenient Deserialize
A Rust crate for **fault-tolerant deserialization** using Serde. Automatically wraps fields to ensure invalid values fall back to sensible defaults — instead of breaking the entire deserialization process.
This is useful when handling user inputs, external APIs, or anything where input reliability is uncertain.
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## ✨ Features
- `Lenient<T>`: wraps any type to gracefully fallback to `T::default()` on deserialization failure.
- `Optional<T>`: alias for `Lenient<Option<T>>`.
- `#[derive(LenientDeserialize)]`: a procedural macro to generate fault-tolerant wrappers for entire structs.
- Support for field-level `#[lenient]` and `#[optional]` attributes.
- Optional error logging via [`tracing`](https://docs.rs/tracing).
- Ergonomic access with `Deref` and `DerefMut` on `Lenient<T>`.
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## 📦 Crate Structure
This workspace contains two crates:
```
lenient/
├── lenient/ # Main library (Lenient wrapper, re-exports macro)
├── lenient_derive/ # Procedural macro crate (LenientDeserialize)
```
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## 🚀 Quick Start
### 1. Add Dependencies
In your `Cargo.toml`:
```toml
[dependencies]
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"
tracing = "0.1"
lenient = { path = "./lenient" }
```
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### 2. Example: Lenient Field Wrapping
```rust
use lenient::LenientDeserialize;
use serde::Deserialize;
#[derive(Debug, Default)]
struct Size(pub usize);
impl<'de> Deserialize<'de> for Size {
fn deserialize<D>(de: D) -> Result<Self, D::Error>
where D: serde::Deserializer<'de> {
let val = usize::deserialize(de)?;
Ok(Size(val))
}
}
#[derive(Debug, Default, LenientDeserialize)]
struct Offset {
#[lenient]
from: Size,
#[optional]
size: Size,
}
```
---
### 3. Example Input Handling with `Deref`
```rust
use serde_json::json;
let input = json!({ "from": "oops", "size": 10 });
let offset: Offset = serde_json::from_value(input).unwrap();
// Access using Deref
let from_val = offset.from.0;
let size_val = offset.size.0;
println!("From: {from_val}, Size: {size_val}");
```
---
## 🧪 Tests
### Run Unit Tests for `lenient`
```sh
cargo test -p lenient
```
### Sample Test
```rust
#[test]
fn test_lenient_invalid() {
let json = r#"{ "value": "invalid" }"#;
#[derive(Debug, Default, PartialEq, Deserialize)]
struct MyType {
value: usize,
}
let result: lenient::Lenient<MyType> = serde_json::from_str(json).unwrap();
assert_eq!(result.value, 0); // defaulted
}
```
---
## 🔖 License
MIT