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78 lines
2.6 KiB
Rust

use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, Attribute, Data, DataStruct, DeriveInput, Error, Ident, Lit, Meta};
#[proc_macro_derive(SettingGroup, attributes(setting_prefix))]
pub fn setting_group(item: TokenStream) -> TokenStream {
let input = parse_macro_input!(item as DeriveInput);
let prefix = setting_prefix(input.attrs.as_ref())
.map(|p| format!("{}_", p))
.unwrap_or_else(|| "".to_string());
stream(input, prefix)
}
fn stream(input: DeriveInput, prefix: String) -> TokenStream {
const ERR_MSG: &str = "Derive macro expects a struct";
match input.data {
Data::Struct(ref data) => struct_stream(input.ident, prefix, data),
Data::Enum(data) => Error::new_spanned(data.enum_token, ERR_MSG)
.to_compile_error()
.into(),
Data::Union(data) => Error::new_spanned(data.union_token, ERR_MSG)
.to_compile_error()
.into(),
}
}
fn struct_stream(name: Ident, prefix: String, data: &DataStruct) -> TokenStream {
let fragments = data.fields.iter().map(|field| match field.ident {
Some(ref ident) => {
let vim_setting_name = format!("{}{}", prefix, ident);
quote! {{
fn update_func(value: rmpv::Value) {
let mut s = crate::settings::SETTINGS.get::<#name>();
s.#ident.from_value(value);
crate::settings::SETTINGS.set(&s);
}
fn reader_func() -> rmpv::Value {
let s = crate::settings::SETTINGS.get::<#name>();
s.#ident.into()
}
crate::settings::SETTINGS.set_setting_handlers(
#vim_setting_name,
update_func,
reader_func
);
}}
}
None => {
Error::new_spanned(field.colon_token, "Expected named struct fields").to_compile_error()
}
});
let expanded = quote! {
impl #name {
pub fn register() {
let s: Self = Default::default();
crate::settings::SETTINGS.set(&s);
#(#fragments)*
}
}
};
TokenStream::from(expanded)
}
fn setting_prefix(attrs: &[Attribute]) -> Option<String> {
for attr in attrs.iter() {
if let Ok(Meta::NameValue(name_value)) = attr.parse_meta() {
if name_value.path.is_ident("setting_prefix") {
if let Lit::Str(literal) = name_value.lit {
return Some(literal.value());
}
}
}
}
None
}