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use proc_macro::TokenStream;
use proc_macro2::Span;
use quote::quote;
use syn::parse::Error;
use syn::spanned::Spanned;
use syn::{parse_macro_input, DeriveInput, Field, Ident};
#[proc_macro_derive(TracerOpts)]
pub fn tracer_opts(input: TokenStream) -> TokenStream {
let input = parse_macro_input!(input as DeriveInput);
match impl_tracer_opts(&input) {
Ok(output) => output,
Err(error) => error.to_compile_error().into(),
}
}
fn impl_tracer_opts(ast: &syn::DeriveInput) -> Result<TokenStream, Error> {
let data = match &ast.data {
syn::Data::Struct(data) => match &data.fields {
syn::Fields::Named(fields) => {
let ident = &ast.ident;
let mut methods = Vec::new();
for field in fields.named.iter() {
let ident = field.ident.as_ref().ok_or_else(|| {
Error::new(
ast.span(),
"TracerOpts is not supported fields of tuple structs",
)
})?;
match extract_opt_type(field) {
Some((cont, ty)) if cont == "Option" => {
methods.push(quote! {
pub fn #ident(mut self, value: impl Into<#ty>) -> Self {
self.#ident = Some(value.into());
self
}
});
let set_ident =
Ident::new(&format!("set_{}", ident), Span::call_site());
methods.push(quote! {
pub fn #set_ident(&mut self, value: impl Into<#ty>) -> &mut Self {
self.#ident = Some(value.into());
self
}
});
}
Some((cont, ty)) if cont == "Vec" => {
methods.push(quote! {
pub fn #ident<T>(mut self, values: impl IntoIterator<Item = T>) -> Self
where
#ty: From<T>,
{
self.#ident.extend(values.into_iter().map(<#ty>::from));
self
}
});
let single = ident.to_string();
let mut chars = single.chars();
chars.next_back();
let single_ident = Ident::new(chars.as_str(), Span::call_site());
methods.push(quote! {
pub fn #single_ident(mut self, value: impl Into<#ty>) -> Self {
self.#ident.push(value.into());
self
}
});
}
_ => {
// Not optional fields skipped, because they can be
// collections and they have to be handeled separately.
// For example, by providing methods link `add_item`.
}
}
}
quote! {
impl #ident {
#( #methods )*
}
}
}
syn::Fields::Unnamed(_) => {
return Err(Error::new(
ast.span(),
"TracerOpts is not supported for tuple structs",
))
}
syn::Fields::Unit => {
return Err(Error::new(
ast.span(),
"TracerOpts is not supported for unit structs",
))
}
},
syn::Data::Enum(_) => {
return Err(Error::new(
ast.span(),
"TracerOpts is not supported for enums",
))
}
syn::Data::Union(_) => {
return Err(Error::new(
ast.span(),
"TracerOpts is not supported for unions",
))
}
};
Ok(data.into())
}
fn extract_opt_type(field: &Field) -> Option<(&syn::Ident, &syn::Type)> {
let path = if let syn::Type::Path(type_path) = &field.ty {
if type_path.qself.is_some() {
return None;
} else {
&type_path.path
}
} else {
return None;
};
let segment = path.segments.last()?;
/*
if segment.ident != "Option" {
return None;
}
*/
let generic_params =
if let syn::PathArguments::AngleBracketed(generic_params) = &segment.arguments {
generic_params
} else {
return None;
};
if let syn::GenericArgument::Type(ty) = generic_params.args.first()? {
Some((&segment.ident, ty))
} else {
None
}
}