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use crate::helper_structs::AttrInnerKeyStringMap;
use crate::helpers::{fold_error_iter, two_segment_path};
use proc_macro2::{Span, TokenStream as TokenStream2};
use syn::{Attribute, Data, DeriveInput, LitStr, Variant};
fn parse_hint_helper_attrs(attrs: &[Attribute]) -> syn::Result<(Vec<LitStr>, Vec<LitStr>)> {
fold_error_iter(
attrs
.iter()
.filter(|a| a.path().get_ident().is_some_and(|i| i == "hint"))
.map(|attr| attr.parse_args::<AttrInnerKeyStringMap>()),
)
.and_then(|v: Vec<AttrInnerKeyStringMap>| {
fold_error_iter(AttrInnerKeyStringMap::multi_into_iter(v).map(|(k, mut v)| match v.len() {
0 => panic!("internal error: a key without values was somehow inserted into the hashmap"),
1 => {
let single_val = v.pop().unwrap();
Ok((LitStr::new(&k.to_string(), Span::call_site()), single_val))
}
_ => {
// the first value is ok, the other ones should error
let after_first = v.into_iter().skip(1);
// this call to fold_error_iter will always return Err with a combined error
fold_error_iter(after_first.map(|lit| Err(syn::Error::new(lit.span(), format!("value for key {k} was already given"))))).map(|_: Vec<()>| unreachable!())
}
}))
})
.map(|v| v.into_iter().unzip())
}
pub fn derive_hint_impl(input_item: TokenStream2) -> syn::Result<TokenStream2> {
let input = syn::parse2::<DeriveInput>(input_item)?;
let ident = input.ident;
match input.data {
Data::Enum(data) => {
let variants = data.variants.iter().map(|var: &Variant| two_segment_path(ident.clone(), var.ident.clone())).collect::<Vec<_>>();
let hint_result = fold_error_iter(data.variants.into_iter().map(|var: Variant| parse_hint_helper_attrs(&var.attrs)));
hint_result.map(|hints: Vec<(Vec<LitStr>, Vec<LitStr>)>| {
let (keys, values): (Vec<Vec<LitStr>>, Vec<Vec<LitStr>>) = hints.into_iter().unzip();
let cap: Vec<usize> = keys.iter().map(|v| v.len()).collect();
quote::quote! {
impl Hint for #ident {
fn hints(&self) -> ::std::collections::HashMap<String, String> {
match self {
#(
#variants { .. } => {
let mut hm = ::std::collections::HashMap::with_capacity(#cap);
#(
hm.insert(#keys.to_string(), #values.to_string());
)*
hm
}
)*
}
}
}
}
})
}
Data::Struct(_) | Data::Union(_) => {
let hint_result = parse_hint_helper_attrs(&input.attrs);
hint_result.map(|(keys, values)| {
let cap = keys.len();
quote::quote! {
impl Hint for #ident {
fn hints(&self) -> ::std::collections::HashMap<String, String> {
let mut hm = ::std::collections::HashMap::with_capacity(#cap);
#(
hm.insert(#keys.to_string(), #values.to_string());
)*
hm
}
}
}
})
}
}
}
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