varienum_macro/
lib.rs

1extern crate proc_macro;
2
3use proc_macro::TokenStream;
4use quote::quote;
5use syn::{DeriveInput, Meta, parse_macro_input};
6
7#[proc_macro_derive(VariantsVec, attributes(description))]
8pub fn variants_vec_derive(item: TokenStream) -> TokenStream {
9    let input = parse_macro_input!(item as DeriveInput);
10    let enum_name = input.ident;
11
12    let data = match input.data {
13        syn::Data::Enum(e) => e,
14        _ => panic!("VariantsVec can only be used on enums"),
15    };
16
17    let mut variants = Vec::new();
18    let mut variants_desc = Vec::new();
19
20    for variant in &data.variants {
21        let ident = &variant.ident;
22
23        // default empty description
24        let mut desc = String::new();
25
26        for attr in &variant.attrs {
27            if attr.path().is_ident("description")
28                && let Meta::NameValue(nv) = &attr.meta
29                && let syn::Expr::Lit(expr_lit) = &nv.value
30                && let syn::Lit::Str(lit_str) = &expr_lit.lit
31            {
32                desc = lit_str.value();
33            }
34        }
35
36        variants.push(ident.to_string());
37        variants_desc.push(quote! {
38            (stringify!(#ident), #desc)
39        });
40    }
41
42    let expanded = quote! {
43        impl varienum::VariantsVec for #enum_name {
44            fn variants() -> &'static [&'static str] {
45                &[#(#variants),*]
46            }
47
48            fn variants_desc() -> &'static [(&'static str, &'static str)] {
49                &[#(#variants_desc),*]
50            }
51        }
52    };
53
54    TokenStream::from(expanded)
55}
56
varienum_macro/lib.rs

varienum_macro/
lib.rs
