macros: Add response attribute macro

crates/ruma-common/src/api.rs

@@ -232,6 +232,9 @@ pub use ruma_macros::ruma_api;
 ///   not just JSON. The field type must be `Vec<u8>`.
 pub use ruma_macros::request;
 
+// TODO: Write docs
+pub use ruma_macros::response;
+
 pub mod error;
 mod metadata;
 

crates/ruma-macros/src/api/api_response.rs

@@ -35,16 +35,7 @@ impl Response {
         let fields = &self.fields;
         quote! {
             #[doc = #docs]
-            #[derive(
+            #[#ruma_macros::response(error = #error_ty)]
-                Clone,
-                Debug,
-                #ruma_macros::Response,
-                #ruma_common::serde::Incoming,
-                #ruma_common::serde::_FakeDeriveSerde,
-            )]
-            #[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
-            #[incoming_derive(!Deserialize, #ruma_macros::_FakeDeriveRumaApi)]
-            #[ruma_api(error = #error_ty)]
             #( #struct_attributes )*
             pub struct #response_ident {
                 #fields

crates/ruma-macros/src/api/response.rs

@@ -6,7 +6,7 @@ use syn::{
     parse::{Parse, ParseStream},
     punctuated::Punctuated,
     visit::Visit,
-    DeriveInput, Field, Generics, Ident, Lifetime, Token, Type,
+    DeriveInput, Field, Generics, Ident, ItemStruct, Lifetime, Token, Type,
 };
 
 use super::attribute::{DeriveResponseMeta, ResponseMeta};
@@ -15,6 +15,42 @@ use crate::util::import_ruma_common;
 mod incoming;
 mod outgoing;
 
+pub fn expand_response(attr: ResponseAttr, item: ItemStruct) -> TokenStream {
+    let ruma_common = import_ruma_common();
+    let ruma_macros = quote! { #ruma_common::exports::ruma_macros };
+
+    let error_ty = attr
+        .0
+        .iter()
+        .find_map(|a| match a {
+            DeriveResponseMeta::Error(ty) => Some(quote! { #ty }),
+            _ => None,
+        })
+        .unwrap_or_else(|| quote! { #ruma_common::api::error::MatrixError });
+
+    quote! {
+        #[derive(
+            Clone,
+            Debug,
+            #ruma_macros::Response,
+            #ruma_common::serde::Incoming,
+            #ruma_common::serde::_FakeDeriveSerde,
+        )]
+        #[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
+        #[incoming_derive(!Deserialize, #ruma_macros::_FakeDeriveRumaApi)]
+        #[ruma_api(error = #error_ty)]
+        #item
+    }
+}
+
+pub struct ResponseAttr(Punctuated<DeriveResponseMeta, Token![,]>);
+
+impl Parse for ResponseAttr {
+    fn parse(input: ParseStream<'_>) -> syn::Result<Self> {
+        Punctuated::<DeriveResponseMeta, Token![,]>::parse_terminated(input).map(Self)
+    }
+}
+
 pub fn expand_derive_response(input: DeriveInput) -> syn::Result<TokenStream> {
     let fields = match input.data {
         syn::Data::Struct(s) => s.fields,

crates/ruma-macros/src/lib.rs

@@ -27,7 +27,7 @@ mod util;
 use self::{
     api::{
         request::{expand_derive_request, expand_request},
-        response::expand_derive_response,
+        response::{expand_derive_response, expand_response},
         Api,
     },
     events::{
@@ -397,6 +397,15 @@ pub fn request(attr: TokenStream, item: TokenStream) -> TokenStream {
     expand_request(attr, item).into()
 }
 
+/// > ⚠ If this is the only documentation you see, please navigate to the docs for
+/// > `ruma_common::api::response`, where actual documentation can be found.
+#[proc_macro_attribute]
+pub fn response(attr: TokenStream, item: TokenStream) -> TokenStream {
+    let attr = parse_macro_input!(attr);
+    let item = parse_macro_input!(item);
+    expand_response(attr, item).into()
+}
+
 /// Internal helper taking care of the request-specific parts of `ruma_api!`.
 #[proc_macro_derive(Request, attributes(ruma_api))]
 pub fn derive_request(input: TokenStream) -> TokenStream {