serde_repr/
lib.rs

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1//! [![github]](https://github.com/dtolnay/serde-repr)&ensp;[![crates-io]](https://crates.io/crates/serde_repr)&ensp;[![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/0.1.13")]
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        impl serde::Serialize for #ident {
65            #[allow(clippy::use_self)]
66            fn serialize<S>(&self, serializer: S) -> core::result::Result<S::Ok, S::Error>
67            where
68                S: serde::Serializer
69            {
70                let value: #repr = match *self {
71                    #(#match_variants)*
72                };
73                serde::Serialize::serialize(&value, serializer)
74            }
75        }
76    })
77}
78
79#[proc_macro_derive(Deserialize_repr, attributes(serde))]
80pub fn derive_deserialize(input: TokenStream) -> TokenStream {
81    let input = parse_macro_input!(input as Input);
82    let ident = input.ident;
83    let repr = input.repr;
84    let variants = input.variants.iter().map(|variant| &variant.ident);
85
86    let declare_discriminants = input.variants.iter().map(|variant| {
87        let variant = &variant.ident;
88        quote! {
89            const #variant: #repr = #ident::#variant as #repr;
90        }
91    });
92
93    let match_discriminants = input.variants.iter().map(|variant| {
94        let variant = &variant.ident;
95        quote! {
96            discriminant::#variant => core::result::Result::Ok(#ident::#variant),
97        }
98    });
99
100    let error_format = match input.variants.len() {
101        1 => "invalid value: {}, expected {}".to_owned(),
102        2 => "invalid value: {}, expected {} or {}".to_owned(),
103        n => "invalid value: {}, expected one of: {}".to_owned() + &", {}".repeat(n - 1),
104    };
105
106    let other_arm = match input.default_variant {
107        Some(variant) => {
108            let variant = &variant.ident;
109            quote! {
110                core::result::Result::Ok(#ident::#variant)
111            }
112        }
113        None => quote! {
114            core::result::Result::Err(serde::de::Error::custom(
115                format_args!(#error_format, other #(, discriminant::#variants)*)
116            ))
117        },
118    };
119
120    TokenStream::from(quote! {
121        impl<'de> serde::Deserialize<'de> for #ident {
122            #[allow(clippy::use_self)]
123            fn deserialize<D>(deserializer: D) -> core::result::Result<Self, D::Error>
124            where
125                D: serde::Deserializer<'de>,
126            {
127                struct discriminant;
128
129                #[allow(non_upper_case_globals)]
130                impl discriminant {
131                    #(#declare_discriminants)*
132                }
133
134                match <#repr as serde::Deserialize>::deserialize(deserializer)? {
135                    #(#match_discriminants)*
136                    other => #other_arm,
137                }
138            }
139        }
140    })
141}
serde_repr/lib.rs

serde_repr/
lib.rs
