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//! [![github]](https://github.com/dtolnay/serde-repr) [![crates-io]](https://crates.io/crates/serde_repr) [![docs-rs]](https://docs.rs/serde_repr)
//!
//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
//!
//! <br>
//!
//! Derive `Serialize` and `Deserialize` that delegates to the underlying repr
//! of a C-like enum.
//!
//! # Examples
//!
//! ```
//! use serde_repr::{Serialize_repr, Deserialize_repr};
//!
//! #[derive(Serialize_repr, Deserialize_repr, PartialEq, Debug)]
//! #[repr(u8)]
//! enum SmallPrime {
//! Two = 2,
//! Three = 3,
//! Five = 5,
//! Seven = 7,
//! }
//!
//! fn main() -> serde_json::Result<()> {
//! let j = serde_json::to_string(&SmallPrime::Seven)?;
//! assert_eq!(j, "7");
//!
//! let p: SmallPrime = serde_json::from_str("2")?;
//! assert_eq!(p, SmallPrime::Two);
//!
//! Ok(())
//! }
//! ```
#![allow(clippy::single_match_else)]
extern crate proc_macro;
mod parse;
use proc_macro::TokenStream;
use quote::quote;
use syn::parse_macro_input;
use crate::parse::Input;
#[proc_macro_derive(Serialize_repr)]
pub fn derive_serialize(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as Input);
let ident = input.ident;
let repr = input.repr;
let match_variants = input.variants.iter().map(|variant| {
let variant = &variant.ident;
quote! {
#ident::#variant => #ident::#variant as #repr,
}
});
TokenStream::from(quote! {
impl serde::Serialize for #ident {
#[allow(clippy::use_self)]
fn serialize<S>(&self, serializer: S) -> core::result::Result<S::Ok, S::Error>
where
S: serde::Serializer
{
let value: #repr = match *self {
#(#match_variants)*
};
serde::Serialize::serialize(&value, serializer)
}
}
})
}
#[proc_macro_derive(Deserialize_repr, attributes(serde))]
pub fn derive_deserialize(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as Input);
let ident = input.ident;
let repr = input.repr;
let variants = input.variants.iter().map(|variant| &variant.ident);
let declare_discriminants = input.variants.iter().map(|variant| {
let variant = &variant.ident;
quote! {
const #variant: #repr = #ident::#variant as #repr;
}
});
let match_discriminants = input.variants.iter().map(|variant| {
let variant = &variant.ident;
quote! {
discriminant::#variant => core::result::Result::Ok(#ident::#variant),
}
});
let error_format = match input.variants.len() {
1 => "invalid value: {}, expected {}".to_owned(),
2 => "invalid value: {}, expected {} or {}".to_owned(),
n => "invalid value: {}, expected one of: {}".to_owned() + &", {}".repeat(n - 1),
};
let other_arm = match input.default_variant {
Some(variant) => {
let variant = &variant.ident;
quote! {
core::result::Result::Ok(#ident::#variant)
}
}
None => quote! {
core::result::Result::Err(serde::de::Error::custom(
format_args!(#error_format, other #(, discriminant::#variants)*)
))
},
};
TokenStream::from(quote! {
impl<'de> serde::Deserialize<'de> for #ident {
#[allow(clippy::use_self)]
fn deserialize<D>(deserializer: D) -> core::result::Result<Self, D::Error>
where
D: serde::Deserializer<'de>,
{
struct discriminant;
#[allow(non_upper_case_globals)]
impl discriminant {
#(#declare_discriminants)*
}
match <#repr as serde::Deserialize>::deserialize(deserializer)? {
#(#match_discriminants)*
other => #other_arm,
}
}
}
})
}