utoipa_repr 0.1.0

Derive utoipa::ToSchema that uses underlying integer representation of enum for schema generation
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# utoipa_repr

[![Crates.io](https://img.shields.io/crates/v/utoipa_repr.svg)](https://crates.io/crates/utoipa_repr)
[![Documentation](https://docs.rs/utoipa_repr/badge.svg)](https://docs.rs/utoipa_repr)
[![License: MIT OR Apache-2.0](https://img.shields.io/badge/License-MIT%20OR%20Apache--2.0-blue.svg)](https://github.com/inomata137/utoipa_repr)

A derive macro for [utoipa](https://github.com/juhaku/utoipa) that provides `ToSchema_repr` functionality, similar to how [serde_repr](https://github.com/dtolnay/serde-repr) works for serde.

This crate allows you to generate OpenAPI schema for enums with `#[repr(...)]` attributes, representing them as their underlying integer types in the schema instead of as enum variants.
<!--
## Features

- 🚀 **Simple**: Just add `#[derive(ToSchema_repr)]` to your repr enum
- 🔧 **Compatible**: Works seamlessly with utoipa's existing schema generation
- 📝 **Type-safe**: Supports all integer repr types (u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize)
- 🎯 **Focused**: Does one thing well - converts repr enums to integer schemas -->

## Installation

Add this to your `Cargo.toml`:

```toml
[dependencies]
utoipa_repr = "0.1"
utoipa = "5.0"
```

## Usage

### Basic Example

```rust
use utoipa_repr::ToSchema_repr;

#[derive(ToSchema_repr)]
#[repr(u8)]
enum Status {
    Pending = 0,
    InProgress = 1,
    Completed = 2,
    Failed = 3,
}

// The generated OpenAPI schema will represent this as:
// {
//   "type": "integer",
//   "format": "int32",
//   "minimum": 0
// }
```

### With Signed Integer Types

```rust
use utoipa_repr::ToSchema_repr;

#[derive(ToSchema_repr)]
#[repr(i32)]
enum Priority {
    Low = -1,
    Normal = 0,
    High = 1,
    Critical = 2,
}

// The generated OpenAPI schema will be:
// {
//   "type": "integer",
//   "format": "int32"
// }
```

## Supported Types

The following `repr` types are supported:

- **Unsigned integers**: `u8`, `u16`, `u32`, `u64`, `u128`, `usize`
- **Signed integers**: `i8`, `i16`, `i32`, `i64`, `i128`, `isize`

### Schema Generation

- **Unsigned types** generate schemas with `"minimum": 0` constraint
- **Signed types** generate schemas without minimum constraint
- All types currently use `"format": "int32"` in the generated schema

## Additional `repr` Attributes

The macro safely ignores other `repr` attributes like `align` and `packed`:

```rust
#[derive(ToSchema_repr)]
#[repr(align(8), u16)]  // align(8) is ignored, u16 is used
enum AlignedEnum {
    A,
    B,
}
```

## Error Handling

The macro will produce compile-time errors in the following cases:

- Missing `#[repr(...)]` attribute
- Unsupported `repr` type
- Invalid `repr` syntax

## License

Licensed under either of [Apache License](./LICENSE-APACHE), Version 2.0, or [MIT License](./LICENSE-MIT) at your option.