axum/axum-macros/src/attr_parsing.rs
2023-03-18 19:23:27 +00:00

102 lines
2.5 KiB
Rust

use quote::ToTokens;
use syn::{
parse::{Parse, ParseStream},
Token,
};
pub(crate) fn parse_parenthesized_attribute<K, T>(
input: ParseStream,
out: &mut Option<(K, T)>,
) -> syn::Result<()>
where
K: Parse + ToTokens,
T: Parse,
{
let kw = input.parse()?;
let content;
syn::parenthesized!(content in input);
let inner = content.parse()?;
if out.is_some() {
let kw_name = std::any::type_name::<K>().split("::").last().unwrap();
let msg = format!("`{kw_name}` specified more than once");
return Err(syn::Error::new_spanned(kw, msg));
}
*out = Some((kw, inner));
Ok(())
}
pub(crate) fn parse_assignment_attribute<K, T>(
input: ParseStream,
out: &mut Option<(K, T)>,
) -> syn::Result<()>
where
K: Parse + ToTokens,
T: Parse,
{
let kw = input.parse()?;
input.parse::<Token![=]>()?;
let inner = input.parse()?;
if out.is_some() {
let kw_name = std::any::type_name::<K>().split("::").last().unwrap();
let msg = format!("`{kw_name}` specified more than once");
return Err(syn::Error::new_spanned(kw, msg));
}
*out = Some((kw, inner));
Ok(())
}
pub(crate) trait Combine: Sized {
fn combine(self, other: Self) -> syn::Result<Self>;
}
pub(crate) fn parse_attrs<T>(ident: &str, attrs: &[syn::Attribute]) -> syn::Result<T>
where
T: Combine + Default + Parse,
{
attrs
.iter()
.filter(|attr| attr.meta.path().is_ident(ident))
.map(|attr| attr.parse_args::<T>())
.try_fold(T::default(), |out, next| out.combine(next?))
}
pub(crate) fn combine_attribute<K, T>(a: &mut Option<(K, T)>, b: Option<(K, T)>) -> syn::Result<()>
where
K: ToTokens,
{
if let Some((kw, inner)) = b {
if a.is_some() {
let kw_name = std::any::type_name::<K>().split("::").last().unwrap();
let msg = format!("`{kw_name}` specified more than once");
return Err(syn::Error::new_spanned(kw, msg));
}
*a = Some((kw, inner));
}
Ok(())
}
pub(crate) fn combine_unary_attribute<K>(a: &mut Option<K>, b: Option<K>) -> syn::Result<()>
where
K: ToTokens,
{
if let Some(kw) = b {
if a.is_some() {
let kw_name = std::any::type_name::<K>().split("::").last().unwrap();
let msg = format!("`{kw_name}` specified more than once");
return Err(syn::Error::new_spanned(kw, msg));
}
*a = Some(kw);
}
Ok(())
}
pub(crate) fn second<T, K>(tuple: (T, K)) -> K {
tuple.1
}