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extern crate proc_macro;
extern crate proc_macro2;
extern crate quote;
extern crate syn;
use proc_macro::TokenStream;
use proc_macro2::*;
use quote::quote;
use std::collections::HashMap;
use syn::DeriveInput;
#[proc_macro_derive(GettersByType)]
pub fn fields_getters_mutable_by_type(input: TokenStream) -> TokenStream {
fields_getters_by_type_impl(input, false)
}
#[proc_macro_derive(GettersMutByType)]
pub fn fields_getters_immutable_by_type(input: TokenStream) -> TokenStream {
fields_getters_by_type_impl(input, true)
}
struct FieldByTypeValue {
immutable_fields: Vec<String>,
mutable_fields: Vec<String>,
ident: syn::Type,
}
impl FieldByTypeValue {
fn new(ident: syn::Type) -> FieldByTypeValue {
FieldByTypeValue {
immutable_fields: vec![],
mutable_fields: vec![],
ident,
}
}
}
fn fields_getters_by_type_impl(input: TokenStream, with_mutability: bool) -> TokenStream {
let ast: DeriveInput = syn::parse(input).unwrap();
let (vis, ty, generics) = (&ast.vis, &ast.ident, &ast.generics);
let mut field_by_type = HashMap::<String, FieldByTypeValue>::new();
match ast.data {
syn::Data::Struct(e) => {
for field in e.fields.iter() {
let mut type_name = String::new();
let mut is_field_mutable: bool = true;
match field.ty {
syn::Type::Path(ref path) => {
add_type_string(&mut type_name, path);
field_by_type
.entry(type_name.clone())
.or_insert_with(|| FieldByTypeValue::new(field.ty.clone()));
}
syn::Type::Reference(ref reference) => {
match *reference.elem {
syn::Type::Path(ref path) => {
add_type_string(&mut type_name, path);
field_by_type.entry(type_name.clone()).or_insert_with(|| {
FieldByTypeValue::new(syn::Type::Path(path.clone()))
});
}
_ => println!("Reference not covered."),
}
is_field_mutable = reference.mutability.is_some();
}
_ => {
println!("Type not covered.");
}
}
match field.ident.as_ref() {
Some(ident) => {
if let Some(field_info) = field_by_type.get_mut(&type_name) {
if is_field_mutable && with_mutability {
field_info.mutable_fields.push(ident.to_string());
}
field_info.immutable_fields.push(ident.to_string());
}
}
None => {
println!("Ident is missing.");
}
}
}
}
_ => panic!("GettersByType can only be derived for structs."),
};
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
let mut ts = Vec::<TokenTree>::new();
for (current_type, field_info) in field_by_type.into_iter() {
let method_return_type = field_info.ident.clone();
let mut add_method = |method_prefix: &str, mutability: bool, mut type_vec: Vec<String>| {
let count = type_vec.len();
let subs_vec = type_vec
.iter_mut()
.map(|i| syn::Ident::new(&i, proc_macro2::Span::call_site()));
let method_name = syn::Ident::new(
&format!("{}_{}", method_prefix, fix_ident(¤t_type)),
proc_macro2::Span::call_site(),
);
let method = if mutability {
quote! {
#vis fn #method_name(&mut self) -> [&mut #method_return_type; #count] {
[#(&mut self.#subs_vec),*]
}
}
} else {
quote! {
#vis fn #method_name(&self) -> [&#method_return_type; #count] {
[#(&self.#subs_vec),*]
}
}
};
ts.extend(method);
};
add_method("get_fields", false, field_info.immutable_fields);
if with_mutability {
add_method("get_mut_fields", true, field_info.mutable_fields);
}
}
let tokens = quote! {
impl #impl_generics #ty #ty_generics
#where_clause
{
#(#ts)
*
}
};
tokens.into()
}
fn add_type_string(type_name: &mut String, path: &syn::TypePath) {
for segment in &path.path.segments {
*type_name += &segment.ident.to_string();
add_argument_string(type_name, &segment.arguments);
}
}
fn add_argument_string(type_name: &mut String, arguments: &syn::PathArguments) {
match arguments {
syn::PathArguments::AngleBracketed(ref angle) => {
*type_name += "<";
for arg in &angle.args {
match arg {
syn::GenericArgument::Type(ref ty) => match ty {
syn::Type::Path(ref argpath) => {
for argsegment in &argpath.path.segments {
*type_name += &format!("{}_", argsegment.ident);
add_argument_string(type_name, &argsegment.arguments);
}
}
_ => println!("Type argument not covered."),
},
_ => println!("Generic argument not covered."),
}
}
*type_name += ">";
}
syn::PathArguments::None => {}
_ => println!("PathArguments not covered."),
}
}
fn fix_ident(name: &str) -> String {
name.to_string()
.to_lowercase()
.chars()
.map(|c| match c {
'<' | '>' => '_',
_ => c,
})
.collect()
}