1//! [![github]](https://github.com/dtolnay/serde-repr) [![crates-io]](https://crates.io/crates/serde_repr) [![docs-rs]](https://docs.rs/serde_repr)
2//!
3//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
4//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
5//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
6//!
7//! <br>
8//!
9//! Derive `Serialize` and `Deserialize` that delegates to the underlying repr
10//! of a C-like enum.
11//!
12//! # Examples
13//!
14//! ```
15//! use serde_repr::{Serialize_repr, Deserialize_repr};
16//!
17//! #[derive(Serialize_repr, Deserialize_repr, PartialEq, Debug)]
18//! #[repr(u8)]
19//! enum SmallPrime {
20//! Two = 2,
21//! Three = 3,
22//! Five = 5,
23//! Seven = 7,
24//! }
25//!
26//! fn main() -> serde_json::Result<()> {
27//! let j = serde_json::to_string(&SmallPrime::Seven)?;
28//! assert_eq!(j, "7");
29//!
30//! let p: SmallPrime = serde_json::from_str("2")?;
31//! assert_eq!(p, SmallPrime::Two);
32//!
33//! Ok(())
34//! }
35//! ```
36
37#![doc(html_root_url = "https://docs.rs/serde_repr/0.1.20")]
38#![allow(clippy::single_match_else)]
39
40extern crate proc_macro;
41
42mod parse;
43
44use proc_macro::TokenStream;
45use quote::quote;
46use syn::parse_macro_input;
47
48use crate::parse::Input;
49
50#[proc_macro_derive(Serialize_repr)]
51pub fn derive_serialize(input: TokenStream) -> TokenStream {
52 let input = parse_macro_input!(input as Input);
53 let ident = input.ident;
54 let repr = input.repr;
55
56 let match_variants = input.variants.iter().map(|variant| {
57 let variant = &variant.ident;
58 quote! {
59 #ident::#variant => #ident::#variant as #repr,
60 }
61 });
62
63 TokenStream::from(quote! {
64 #[allow(deprecated)]
65 impl serde::Serialize for #ident {
66 #[allow(clippy::use_self)]
67 fn serialize<S>(&self, serializer: S) -> ::core::result::Result<S::Ok, S::Error>
68 where
69 S: serde::Serializer
70 {
71 let value: #repr = match *self {
72 #(#match_variants)*
73 };
74 serde::Serialize::serialize(&value, serializer)
75 }
76 }
77 })
78}
79
80#[proc_macro_derive(Deserialize_repr, attributes(serde))]
81pub fn derive_deserialize(input: TokenStream) -> TokenStream {
82 let input = parse_macro_input!(input as Input);
83 let ident = input.ident;
84 let repr = input.repr;
85 let variants = input.variants.iter().map(|variant| &variant.ident);
86
87 let declare_discriminants = input.variants.iter().map(|variant| {
88 let variant = &variant.ident;
89 quote! {
90 const #variant: #repr = #ident::#variant as #repr;
91 }
92 });
93
94 let match_discriminants = input.variants.iter().map(|variant| {
95 let variant = &variant.ident;
96 quote! {
97 discriminant::#variant => ::core::result::Result::Ok(#ident::#variant),
98 }
99 });
100
101 let error_format = match input.variants.len() {
102 1 => "invalid value: {}, expected {}".to_owned(),
103 2 => "invalid value: {}, expected {} or {}".to_owned(),
104 n => "invalid value: {}, expected one of: {}".to_owned() + &", {}".repeat(n - 1),
105 };
106
107 let other_arm = match input.default_variant {
108 Some(variant) => {
109 let variant = &variant.ident;
110 quote! {
111 ::core::result::Result::Ok(#ident::#variant)
112 }
113 }
114 None => quote! {
115 ::core::result::Result::Err(serde::de::Error::custom(
116 format_args!(#error_format, other #(, discriminant::#variants)*)
117 ))
118 },
119 };
120
121 TokenStream::from(quote! {
122 #[allow(deprecated)]
123 impl<'de> serde::Deserialize<'de> for #ident {
124 #[allow(clippy::use_self)]
125 fn deserialize<D>(deserializer: D) -> ::core::result::Result<Self, D::Error>
126 where
127 D: serde::Deserializer<'de>,
128 {
129 #[allow(non_camel_case_types)]
130 struct discriminant;
131
132 #[allow(non_upper_case_globals)]
133 impl discriminant {
134 #(#declare_discriminants)*
135 }
136
137 match <#repr as serde::Deserialize>::deserialize(deserializer)? {
138 #(#match_discriminants)*
139 other => #other_arm,
140 }
141 }
142 }
143 })
144}
145