kynos-macros 0.2.0

//! `#[derive(CookieParams)]`.

use proc_macro::TokenStream;
use quote::quote;
use syn::{DeriveInput, parse_macro_input};

use crate::derive::{
    common::{named_fields, names_const, reject_duplicate_names, wire_name},
    params::{Param, construct, decode_field, parameters_body},
};

pub(crate) fn expand(item: TokenStream) -> TokenStream {
    let input = parse_macro_input!(item as DeriveInput);
    match expand_inner(&input) {
        Ok(tokens) => tokens.into(),
        Err(error) => error.to_compile_error().into(),
    }
}

fn expand_inner(input: &DeriveInput) -> syn::Result<proc_macro2::TokenStream> {
    let fields = named_fields(input, "Cookies")?;
    let names = fields
        .named
        .iter()
        .map(|field| wire_name(field, "cookie"))
        .collect::<syn::Result<Vec<_>>>()?;
    reject_duplicate_names(fields, &names, "cookie")?;

    let name = &input.ident;
    let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();
    let names_item = names_const(&names);

    let params = Param::pair(fields, &names);
    let rejection = quote!(::kynos::error::rejection::CookieRejection);

    // Splitting a jar is `http::cookie`'s job, not an expansion's: the rules
    // are RFC 6265's, they belong in one place, and a credential carried in a
    // cookie reads them from there in a build with no `cookie` feature at all.
    let reads = params.iter().map(|param| {
        let wire = param.name();
        let found = quote! {
            ::kynos::http::cookie::value_of(headers, #wire)
        };
        decode_field(param, &rejection, &found, "the cookie is required")
    });
    let value = construct(&params);

    let parameters = parameters_body(
        &params,
        &quote!(::kynos::openapi::ParameterIn::Cookie),
        false,
    );

    Ok(quote! {
        impl #impl_generics ::kynos::extract::params::cookie::CookieParams
            for #name #ty_generics #where_clause
        {
            #names_item

            fn decode(
                headers: &::kynos::http::HeaderMap,
            ) -> ::core::result::Result<Self, ::kynos::error::rejection::CookieRejection> {
                #(#reads)*
                #value
            }

            fn parameters(
                registry: &mut ::kynos::schema::registry::Registry,
            ) -> ::std::vec::Vec<::kynos::openapi::Parameter> {
                #parameters
            }
        }
    })
}