53 lines
1.5 KiB
Rust
53 lines
1.5 KiB
Rust
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use proc_macro::TokenStream;
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use syn::{spanned::Spanned, Data, Fields};
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#[proc_macro_derive(Extract)]
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pub fn extract(input: TokenStream) -> TokenStream {
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let ast = syn::parse_macro_input!(input);
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impl_extract(&ast)
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}
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fn impl_extract(ast: &syn::DeriveInput) -> TokenStream {
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let name = &ast.ident;
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match &ast.data {
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Data::Struct(st) => match &st.fields {
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Fields::Named(fields) => {
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let extracted = fields.named.iter().map(|field| {
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let ident = &field.ident;
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let ty = &field.ty;
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quote::quote_spanned! {field.span()=>
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#ident : crate::utils::extract_arg!(ctx, #ident, #ty)
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}
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});
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TokenStream::from(quote::quote! {
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impl Extract for #name {
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fn extract(ctx: crate::ApplicationContext) -> Self {
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Self {
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#(#extracted,)*
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}
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}
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}
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})
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}
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Fields::Unit => TokenStream::from(quote::quote! {
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impl Extract for #name {
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fn extract(ctx: crate::ApplicationContext) -> Self {
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Self {}
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}
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}
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}),
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_ => {
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panic!("Only named/unit structs can derive Extract");
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}
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},
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_ => {
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panic!("Only structs can derive Extract");
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}
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}
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}
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