use proc_macro2::TokenStream;
use quote::quote;
use serde_derive_internals::{ast as serde_ast, Ctxt, Derive};
use syn::DeriveInput;
pub(crate) fn serialize_fields(input: DeriveInput) -> TokenStream {
let cx = Ctxt::new();
let serde_container = serde_ast::Container::from_ast(&cx, &input, Derive::Serialize);
cx.check().unwrap();
let container = serde_container.expect("failed to get serde attrs for container");
match &container.data {
serde_ast::Data::Struct(style, vec) => match style {
serde_ast::Style::Struct => {
let struct_name = &container.ident;
let struct_name_str = container.attrs.name().serialize_name();
let num_unflattened_fields =
vec.iter().filter(|field| !field.attrs.flatten()).count();
let num_fields = vec.iter().filter(|field| field.attrs.flatten()).fold(
quote! { #num_unflattened_fields },
|num_fields, field| {
let ty = field.ty;
quote! { #num_fields + <#ty as serde_fast_flatten::SerializeFields>::NUM_FIELDS }
},
);
let serialize_fields = vec.iter().fold(quote!(), |serialize_fields, field| {
let field_name = match &field.member {
syn::Member::Named(ident) => ident,
syn::Member::Unnamed(_) => {
panic!("unnamed field in named field struct")
}
};
let serialize_field = if field.attrs.flatten() {
quote!(self.#field_name.serialize_fields(s)?;)
} else {
let field_name_str = field.attrs.name().serialize_name();
quote!(s.serialize_field(#field_name_str, &self.#field_name)?;)
};
quote!(#serialize_fields #serialize_field)
});
quote!(const _ : () = {
use serde::{Serialize, Serializer, ser::SerializeStruct};
use serde_fast_flatten::SerializeFields;
impl Serialize for #struct_name {
#[inline]
fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
where
S: serde::Serializer,
{
let mut s = serializer.serialize_struct(#struct_name_str, Self::NUM_FIELDS)?;
self.serialize_fields(&mut s)?;
s.end()
}
}
impl SerializeFields for #struct_name {
const NUM_FIELDS : usize = #num_fields;
#[inline]
fn serialize_fields<S: SerializeStruct>(
&self,
s: &mut S
) -> std::result::Result<(), S::Error> {
#serialize_fields
Ok(())
}
}
};)
}
_ => panic!("SerializeFields cannot be auto-derived for struct without named fields"),
},
serde_ast::Data::Enum(_) => panic!("SerializeFields cannot be auto-derived for enum"),
}
}