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use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use quote::{format_ident, quote};
use syn::{DataEnum, Ident};
pub fn derive_deserialize(ident: Ident, data_enum: DataEnum) -> TokenStream {
let visitor = format_ident!("{}Visitor", ident);
// Create match arm streams and get a list with all available values.
let mut match_arms_stream = TokenStream2::new();
let mut available_values = String::from("one of ");
for variant in data_enum.variants.iter().filter(|variant| {
// Skip deserialization for `#[config(skip)]` fields.
variant.attrs.iter().all(|attr| {
!crate::path_ends_with(&attr.path, "config") || attr.tokens.to_string() != "(skip)"
})
}) {
let variant_ident = &variant.ident;
let variant_str = variant_ident.to_string();
available_values = format!("{}`{}`, ", available_values, variant_str);
let literal = variant_str.to_lowercase();
match_arms_stream.extend(quote! {
#literal => Ok(#ident :: #variant_ident),
});
}
// Remove trailing `, ` from the last enum variant.
available_values.truncate(available_values.len().saturating_sub(2));
// Generate deserialization impl.
let tokens = quote! {
struct #visitor;
impl<'de> serde::de::Visitor<'de> for #visitor {
type Value = #ident;
fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
formatter.write_str(#available_values)
}
fn visit_str<E>(self, s: &str) -> Result<Self::Value, E>
where
E: serde::de::Error,
{
match s.to_lowercase().as_str() {
#match_arms_stream
_ => Err(E::custom(
&format!("unknown variant `{}`, expected {}", s, #available_values)
)),
}
}
}
impl<'de> serde::Deserialize<'de> for #ident {
fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
where
D: serde::Deserializer<'de>,
{
deserializer.deserialize_str(#visitor)
}
}
};
tokens.into()
}
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