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extern crate proc_macro;
use proc_macro2::{TokenStream, Ident};
use quote::{quote, quote_spanned};
use syn::spanned::Spanned;
use syn::{parse_macro_input, Data, DeriveInput, Fields, Index};
#[proc_macro_derive(RedactedDebug, attributes(redacted))]
pub fn derive_redacted_debug(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
let input = parse_macro_input!(input as DeriveInput);
let name = input.ident;
let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
let body = redacted_debug_body(&name, &input.data);
#[cfg(feature = "std")]
let (trayt, formatter) = (quote!(::std::fmt::Debug), quote!(::std::fmt::Formatter));
#[cfg(not(feature = "std"))]
let (trayt, formatter) = (quote!(::core::fmt::Debug), quote!(::core::fmt::Formatter));
let expanded = quote! {
impl #impl_generics #trayt for #name #ty_generics #where_clause {
fn fmt(&self, f: &mut #formatter) -> ::std::fmt::Result {
#body
}
}
};
proc_macro::TokenStream::from(expanded)
}
fn is_redacted(attrs: &Vec<syn::Attribute>) -> bool {
for attr in attrs {
if attr.path.is_ident("redacted") {
return true
}
}
false
}
fn redacted_debug_body(name: &Ident, data: &Data) -> TokenStream {
match *data {
Data::Struct(ref data) => {
match data.fields {
Fields::Named(ref fields) => {
let recurse = fields.named.iter().map(|f| {
let name = &f.ident;
if is_redacted(&f.attrs) {
quote_spanned! {f.span()=>
.field(stringify!(#name), &"\"...\"")
}
} else {
quote_spanned! {f.span()=>
.field(stringify!(#name), &self.#name)
}
}
});
quote! {
f.debug_struct(stringify!(#name))
#(#recurse)*
.finish()
}
}
Fields::Unnamed(ref fields) => {
let recurse = fields.unnamed.iter().enumerate().map(|(i, f)| {
let index = Index::from(i);
if is_redacted(&f.attrs) {
quote_spanned! {f.span()=>
.field(&"\"...\"")
}
} else {
quote_spanned! {f.span()=>
.field(&self.#index)
}
}
});
quote! {
f.debug_tuple(stringify!(#name))
#(#recurse)*
.finish()
}
}
Fields::Unit => {
quote! {
write!(f, stringify!(#name))
}
}
}
}
Data::Enum(ref data) => {
let variants = data.variants.iter().map(|v| {
let name = &v.ident;
match v.fields {
Fields::Named(ref fields) => {
let recurse = fields.named.iter().map(|f| {
let name = &f.ident;
if is_redacted(&f.attrs) {
quote_spanned! {f.span()=>
.field(stringify!(#name), &"\"...\"")
}
} else {
quote_spanned! {f.span()=>
.field(stringify!(#name), &self.#name)
}
}
});
quote! {
f.debug_struct(stringify!(#name))
#(#recurse)*
.finish()
}
}
Fields::Unnamed(ref fields) => {
let recurse = fields.unnamed.iter().enumerate().map(|(i, f)| {
let index = Index::from(i);
if is_redacted(&f.attrs) {
quote_spanned! {f.span()=>
.field(&"\"...\"")
}
} else {
quote_spanned! {f.span()=>
.field(&self.#index)
}
}
});
quote! {
#name => {
f.debug_tuple(stringify!(#name))
#(#recurse)*
.finish()
}
}
}
Fields::Unit => {
quote! {
#name => {
write!(f, stringify!(#name))
}
}
}
}
});
quote! {
match self {
#(#variants,)*
}
}
}
Data::Union(_) => panic!("this trait cannot be derived for unions"),
}
}