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use proc_macro::TokenStream;
use syn::parse::{Parse, ParseStream, Result};
use syn::spanned::Spanned;
use syn::{parse_macro_input, LitStr, Token};
use quote::quote;
#[derive(Debug, Default)]
struct RenameArgs {
name: Option<String>,
prepend: Option<String>,
append: Option<String>,
}
mod keyword {
syn::custom_keyword!(name);
syn::custom_keyword!(prepend);
syn::custom_keyword!(append);
}
macro_rules! parse_keyword {
($fn_name: ident, $keyword: path) => {
fn $fn_name (input: ParseStream) -> Result<String> {
input.parse::<$keyword>()?;
input.parse::<Token![=]>()?;
let value: LitStr = input.parse()?;
let _ = input.parse::<Token![,]>();
Ok(value.value())
}
};
}
impl RenameArgs {
parse_keyword!(parse_name, keyword::name);
parse_keyword!(parse_prepend, keyword::prepend);
parse_keyword!(parse_append, keyword::append);
}
impl Parse for RenameArgs {
fn parse(input: ParseStream) -> Result<Self> {
Ok(RenameArgs {
name: Self::parse_name(input).ok(),
prepend: Self::parse_prepend(input).ok(),
append: Self::parse_append(input).ok(),
})
}
}
#[proc_macro_attribute]
pub fn rename(args: TokenStream, input: TokenStream) -> TokenStream {
let args = parse_macro_input!(args as RenameArgs);
let mut input = parse_macro_input!(input as syn::ItemStruct);
let mut result = input.ident.to_string();
if let Some(name) = args.name {
result = name;
}
if let Some(prepend) = args.prepend {
result.insert_str(0, &prepend);
}
if let Some(append) = args.append {
result.push_str(&append);
}
input.ident = syn::Ident::new(&result, input.span());
let expanded = quote! {
#input
};
expanded.into()
}