restify-macros 0.0.6

STILL WIP
Documentation 
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use quote::ToTokens;
use syn::parse::{Parse, ParseStream};

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) 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 second<T, K>(tuple: (T, K)) -> K {
  tuple.1
}