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#![recursion_limit = "256"]
extern crate proc_macro;
use quote::quote;
use proc_macro2::TokenStream;
fn field_schema_names<'a>(
fields: impl Iterator<Item = &'a syn::Field> + 'a,
) -> impl Iterator<Item = syn::Ident> + 'a {
fields.map(|field| {
let mut name = field.ident.clone().unwrap();
for attr in &field.attrs {
if let Ok(syn::Meta::List(syn::MetaList {
path: ref meta_path,
ref nested,
..
})) = attr.parse_meta()
{
if meta_path.is_ident("trans") {
for inner in nested {
match *inner {
syn::NestedMeta::Meta(syn::Meta::NameValue(syn::MetaNameValue {
path: ref meta_path,
lit: syn::Lit::Str(ref lit),
..
})) => {
if meta_path.is_ident("rename") {
name = syn::Ident::new(&lit.value(), lit.span());
}
}
_ => panic!("Unexpected meta"),
}
}
}
}
}
name
})
}
#[proc_macro_derive(Trans, attributes(trans))]
pub fn derive_trans(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input: TokenStream = input.into();
let result: TokenStream = {
let ast: syn::DeriveInput = syn::parse_str(&input.to_string()).unwrap();
let input_type = &ast.ident;
let generic_params: Vec<_> = ast
.generics
.type_params()
.map(|param| ¶m.ident)
.collect();
let generic_params = &generic_params;
let mut base_name =
syn::LitStr::new(&ast.ident.to_string(), proc_macro2::Span::call_site());
let mut magic: Option<syn::Expr> = None;
let mut generics_in_name = true;
for attr in &ast.attrs {
if let Ok(syn::Meta::List(syn::MetaList {
path: ref meta_path,
ref nested,
..
})) = attr.parse_meta()
{
if meta_path.is_ident("trans") {
for inner in nested {
match *inner {
syn::NestedMeta::Meta(syn::Meta::NameValue(syn::MetaNameValue {
path: ref meta_path,
lit: syn::Lit::Str(ref lit),
..
})) => {
if meta_path.is_ident("rename") {
base_name = lit.clone();
} else if meta_path.is_ident("magic") {
magic = Some(syn::parse_str(&lit.value()).unwrap());
}
}
syn::NestedMeta::Meta(syn::Meta::Path(ref meta_path)) => {
if meta_path.is_ident("no_generics_in_name") {
generics_in_name = false;
}
}
_ => panic!("Unexpected meta"),
}
}
}
}
}
let (magic_write, magic_read) = match &magic {
Some(magic) => (
quote! {
<i32 as trans::Trans>::write_to(&#magic, writer)?;
},
quote! {
assert_eq!(<i32 as trans::Trans>::read_from(reader)?, #magic);
},
),
None => (quote! {}, quote! {}),
};
let magic_value = match &magic {
Some(expr) => quote! { Some(#expr) },
None => quote! { None },
};
let final_name = quote! {{
let mut name = #base_name.to_owned();
if #generics_in_name {
#(
name += &trans::Schema::of::<#generic_params>().full_name().raw();
)*
}
name
}};
match ast.data {
syn::Data::Struct(syn::DataStruct { ref fields, .. }) => match fields {
syn::Fields::Named(_) => {
let field_tys: Vec<_> = fields.iter().map(|field| &field.ty).collect();
let field_tys = &field_tys;
let field_schema_names: Vec<_> = field_schema_names(fields.iter()).collect();
let field_names: Vec<_> = fields
.iter()
.map(|field| field.ident.as_ref().unwrap())
.collect();
let field_names = &field_names;
let mut generics = ast.generics.clone();
let extra_where_clauses = quote! {
where
#(#field_tys: trans::Trans,)*
#(#generic_params: trans::Trans,)*
};
let extra_where_clauses: syn::WhereClause =
syn::parse_str(&extra_where_clauses.to_string()).unwrap();
generics
.make_where_clause()
.predicates
.extend(extra_where_clauses.predicates);
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let expanded = quote! {
impl #impl_generics trans::Trans for #input_type #ty_generics #where_clause {
fn create_schema() -> trans::Schema {
let name = #final_name;
trans::Schema::Struct(trans::Struct {
name: trans::Name::new(name),
magic: #magic_value,
fields: vec![
#(trans::Field {
name: trans::Name::new(stringify!(#field_schema_names).to_owned()),
schema: trans::Schema::of::<#field_tys>(),
}),*
],
})
}
fn write_to(&self, writer: &mut dyn std::io::Write) -> std::io::Result<()> {
#magic_write
#(trans::Trans::write_to(&self.#field_names, writer)?;)*
Ok(())
}
fn read_from(reader: &mut dyn std::io::Read) -> std::io::Result<Self> {
#magic_read
Ok(Self {
#(#field_names: trans::Trans::read_from(reader)?),*
})
}
}
};
expanded.into()
}
syn::Fields::Unnamed(_) => {
if fields.iter().len() != 1 {
panic!("Tuple structs other than newtype not supported");
}
if magic.is_some() {
panic!("Magic with newtypes not supported");
}
let inner_ty = fields.iter().next().unwrap();
let mut generics = ast.generics.clone();
let extra_where_clauses = quote! {
where #inner_ty: trans::Trans + 'static
};
let extra_where_clauses: syn::WhereClause =
syn::parse_str(&extra_where_clauses.to_string()).unwrap();
generics
.make_where_clause()
.predicates
.extend(extra_where_clauses.predicates);
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let expanded = quote! {
impl #impl_generics trans::Trans for #input_type #ty_generics #where_clause {
fn create_schema() -> trans::Schema {
<#inner_ty as trans::Trans>::create_schema()
}
fn write_to(&self, writer: &mut dyn std::io::Write) -> std::io::Result<()> {
trans::Trans::write_to(&self.0, writer)?;
Ok(())
}
fn read_from(reader: &mut dyn std::io::Read) -> std::io::Result<Self> {
Ok(Self(trans::Trans::read_from(reader)?))
}
}
};
expanded.into()
}
syn::Fields::Unit => panic!("Unit structs not supported"),
},
syn::Data::Enum(syn::DataEnum { ref variants, .. }) => {
let mut generics = ast.generics.clone();
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let read_write_impl = {
let variant_writes = variants.iter().enumerate().map(|(tag, variant)| {
let tag = tag as i32;
let variant_name = &variant.ident;
let field_names: Vec<_> = variant
.fields
.iter()
.map(|field| {
field
.ident
.as_ref()
.expect("Only named fields are supported")
})
.collect();
let field_names = &field_names;
let field_names_copy = field_names;
quote! {
#input_type::#variant_name { #(#field_names,)* } => {
trans::Trans::write_to(&#tag, writer)?;
#(trans::Trans::write_to(#field_names_copy, writer)?;)*
}
}
});
let variant_reads = variants.iter().enumerate().map(|(tag, variant)| {
let tag = tag as i32;
let variant_name = &variant.ident;
let field_names = variant
.fields
.iter()
.map(|field| field.ident.as_ref().unwrap());
quote! {
#tag => #input_type::#variant_name {
#(#field_names: trans::Trans::read_from(reader)?,)*
},
}
});
quote! {
fn write_to(&self, writer: &mut dyn std::io::Write) -> std::io::Result<()> {
match self {
#(#variant_writes)*
}
Ok(())
}
fn read_from(reader: &mut dyn std::io::Read) -> std::io::Result<Self> {
Ok(match <i32 as trans::Trans>::read_from(reader)? {
#(#variant_reads)*
tag => {
return Err(std::io::Error::new(
std::io::ErrorKind::Other,
format!("Unexpected tag {:?}", tag)));
}
})
}
}
};
if variants.iter().all(|variant| {
if let syn::Fields::Unit = variant.fields {
true
} else {
false
}
}) {
let variants = variants.iter();
let expanded = quote! {
impl #impl_generics trans::Trans for #input_type #ty_generics #where_clause {
fn create_schema() -> trans::Schema {
let base_name = #final_name;
trans::Schema::Enum {
base_name: trans::Name::new(base_name),
variants: vec![#(trans::Name::new(stringify!(#variants).to_owned())),*],
}
}
#read_write_impl
}
};
expanded.into()
} else {
let variants = variants.iter().map(|variant| {
let variant_name = &variant.ident;
let field_schema_names = field_schema_names(variant.fields.iter());
let field_tys = variant.fields.iter().map(|field| &field.ty);
quote! {
trans::Struct {
name: trans::Name::new(stringify!(#variant_name).to_owned()),
magic: None,
fields: vec![
#(trans::Field {
name: trans::Name::new(stringify!(#field_schema_names).to_owned()),
schema: trans::Schema::of::<#field_tys>(),
}),*
],
}
}
});
let expanded = quote! {
impl #impl_generics trans::Trans for #input_type #ty_generics #where_clause {
fn create_schema() -> trans::Schema {
let base_name = #final_name;
trans::Schema::OneOf {
base_name: trans::Name::new(base_name),
variants: vec![#(#variants),*],
}
}
#read_write_impl
}
};
expanded.into()
}
}
syn::Data::Union(_) => panic!("Unions not supported"),
}
};
result.into()
}