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&logoColor=white&logo=data:image/svg+xml;base64,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
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 #![allow(clippy::single_match_else)]
38
39 extern crate proc_macro;
40
41 mod parse;
42
43 use proc_macro::TokenStream;
44 use quote::quote;
45 use syn::parse_macro_input;
46
47 use crate::parse::Input;
48
49 use std::iter;
50
51 #[proc_macro_derive(Serialize_repr)]
derive_serialize(input: TokenStream) -> TokenStream52 pub fn derive_serialize(input: TokenStream) -> TokenStream {
53 let input = parse_macro_input!(input as Input);
54 let ident = input.ident;
55 let repr = input.repr;
56
57 let match_variants = input.variants.iter().map(|variant| {
58 let variant = &variant.ident;
59 quote! {
60 #ident::#variant => #ident::#variant as #repr,
61 }
62 });
63
64 TokenStream::from(quote! {
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))]
derive_deserialize(input: TokenStream) -> TokenStream81 pub 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 => {
105 "invalid value: {}, expected one of: {}".to_owned()
106 + &iter::repeat(", {}").take(n - 1).collect::<String>()
107 }
108 };
109
110 let other_arm = match input.default_variant {
111 Some(variant) => {
112 let variant = &variant.ident;
113 quote! {
114 core::result::Result::Ok(#ident::#variant)
115 }
116 }
117 None => quote! {
118 core::result::Result::Err(serde::de::Error::custom(
119 format_args!(#error_format, other #(, discriminant::#variants)*)
120 ))
121 },
122 };
123
124 TokenStream::from(quote! {
125 impl<'de> serde::Deserialize<'de> for #ident {
126 #[allow(clippy::use_self)]
127 fn deserialize<D>(deserializer: D) -> core::result::Result<Self, D::Error>
128 where
129 D: serde::Deserializer<'de>,
130 {
131 struct discriminant;
132
133 #[allow(non_upper_case_globals)]
134 impl discriminant {
135 #(#declare_discriminants)*
136 }
137
138 match <#repr as serde::Deserialize>::deserialize(deserializer)? {
139 #(#match_discriminants)*
140 other => #other_arm,
141 }
142 }
143 }
144 })
145 }
146