api: Allow cfg attributes on rate_limited and authentication metadata fields

ruma-api-macros/src/api.rs

@@ -83,8 +83,32 @@ pub fn expand_all(api: Api) -> syn::Result<TokenStream> {
     // with only the literal's value from here on.
     let name = &api.metadata.name.value();
     let path = &api.metadata.path;
-    let rate_limited = &api.metadata.rate_limited;
-    let authentication = &api.metadata.authentication;
+    let rate_limited: TokenStream = api
+        .metadata
+        .rate_limited
+        .iter()
+        .map(|r| {
+            let attrs = &r.attrs;
+            let value = &r.value;
+            quote! {
+                #( #attrs )*
+                rate_limited: #value,
+            }
+        })
+        .collect();
+    let authentication: TokenStream = api
+        .metadata
+        .authentication
+        .iter()
+        .map(|r| {
+            let attrs = &r.attrs;
+            let value = &r.value;
+            quote! {
+                #( #attrs )*
+                authentication: #ruma_api::AuthScheme::#value,
+            }
+        })
+        .collect();
 
     let request_type = &api.request;
     let response_type = &api.response;
@@ -118,20 +142,24 @@ pub fn expand_all(api: Api) -> syn::Result<TokenStream> {
     };
 
     let mut header_kvs = api.request.append_header_kvs();
-    if authentication == "AccessToken" {
-        header_kvs.extend(quote! {
-            req_headers.insert(
-                #http::header::AUTHORIZATION,
-                #http::header::HeaderValue::from_str(
-                    &::std::format!(
-                        "Bearer {}",
-                        access_token.ok_or(
-                            #ruma_api::error::IntoHttpError::NeedsAuthentication
-                        )?
-                    )
-                )?
-            );
-        });
+    for auth in &api.metadata.authentication {
+        if auth.value == "AccessToken" {
+            let attrs = &auth.attrs;
+            header_kvs.extend(quote! {
+                #( #attrs )*
+                req_headers.insert(
+                    #http::header::AUTHORIZATION,
+                    #http::header::HeaderValue::from_str(
+                        &::std::format!(
+                            "Bearer {}",
+                            access_token.ok_or(
+                                #ruma_api::error::IntoHttpError::NeedsAuthentication
+                            )?
+                        )
+                    )?
+                );
+            });
+        }
     }
 
     let extract_request_headers = if api.request.has_header_fields() {
@@ -227,19 +255,29 @@ pub fn expand_all(api: Api) -> syn::Result<TokenStream> {
     let error = &api.error_ty;
     let request_lifetimes = api.request.combine_lifetimes();
 
-    let non_auth_endpoint_impls = if authentication != "None" {
-        TokenStream::new()
-    } else {
-        quote! {
-            #[automatically_derived]
-            impl #request_lifetimes #ruma_api::OutgoingNonAuthRequest
-                for Request #request_lifetimes
-            {}
+    let non_auth_endpoint_impls: TokenStream = api
+        .metadata
+        .authentication
+        .iter()
+        .map(|auth| {
+            if auth.value != "None" {
+                TokenStream::new()
+            } else {
+                let attrs = &auth.attrs;
+                quote! {
+                    #( #attrs )*
+                    #[automatically_derived]
+                    impl #request_lifetimes #ruma_api::OutgoingNonAuthRequest
+                        for Request #request_lifetimes
+                        {}
 
-            #[automatically_derived]
-            impl #ruma_api::IncomingNonAuthRequest for #incoming_request_type {}
-        }
-    };
+                    #( #attrs )*
+                    #[automatically_derived]
+                    impl #ruma_api::IncomingNonAuthRequest for #incoming_request_type {}
+                }
+            }
+        })
+        .collect();
 
     Ok(quote! {
         #[doc = #request_doc]
@@ -301,8 +339,8 @@ pub fn expand_all(api: Api) -> syn::Result<TokenStream> {
             method: #http::Method::#method,
             name: #name,
             path: #path,
-            rate_limited: #rate_limited,
-            authentication: #ruma_api::AuthScheme::#authentication,
+            #rate_limited
+            #authentication
         };
 
         #[automatically_derived]

ruma-api-macros/src/api/metadata.rs

@@ -4,7 +4,7 @@ use quote::ToTokens;
 use syn::{
     braced,
     parse::{Parse, ParseStream},
-    Ident, LitBool, LitStr, Token,
+    Attribute, Ident, LitBool, LitStr, Token,
 };
 
 use crate::util;
@@ -19,6 +19,15 @@ mod kw {
     syn::custom_keyword!(authentication);
 }
 
+/// A field of Metadata that contains attribute macros
+pub struct MetadataField<T> {
+    /// attributes over the field
+    pub attrs: Vec<Attribute>,
+
+    /// the field itself
+    pub value: T,
+}
+
 /// The result of processing the `metadata` section of the macro.
 pub struct Metadata {
     /// The description field.
@@ -34,10 +43,10 @@ pub struct Metadata {
     pub path: LitStr,
 
     /// The rate_limited field.
-    pub rate_limited: LitBool,
+    pub rate_limited: Vec<MetadataField<LitBool>>,
 
     /// The authentication field.
-    pub authentication: Ident,
+    pub authentication: Vec<MetadataField<Ident>>,
 }
 
 fn set_field<T: ToTokens>(field: &mut Option<T>, value: T) -> syn::Result<()> {
@@ -69,8 +78,8 @@ impl Parse for Metadata {
         let mut method = None;
         let mut name = None;
         let mut path = None;
-        let mut rate_limited = None;
-        let mut authentication = None;
+        let mut rate_limited = vec![];
+        let mut authentication = vec![];
 
         for field_value in field_values {
             match field_value {
@@ -78,8 +87,12 @@ impl Parse for Metadata {
                 FieldValue::Method(m) => set_field(&mut method, m)?,
                 FieldValue::Name(n) => set_field(&mut name, n)?,
                 FieldValue::Path(p) => set_field(&mut path, p)?,
-                FieldValue::RateLimited(rl) => set_field(&mut rate_limited, rl)?,
-                FieldValue::Authentication(a) => set_field(&mut authentication, a)?,
+                FieldValue::RateLimited(value, attrs) => {
+                    rate_limited.push(MetadataField { value, attrs })
+                }
+                FieldValue::Authentication(value, attrs) => {
+                    authentication.push(MetadataField { value, attrs })
+                }
             }
         }
 
@@ -91,8 +104,16 @@ impl Parse for Metadata {
             method: method.ok_or_else(|| missing_field("method"))?,
             name: name.ok_or_else(|| missing_field("name"))?,
             path: path.ok_or_else(|| missing_field("path"))?,
-            rate_limited: rate_limited.ok_or_else(|| missing_field("rate_limited"))?,
-            authentication: authentication.ok_or_else(|| missing_field("authentication"))?,
+            rate_limited: if rate_limited.is_empty() {
+                return Err(missing_field("rate_limited"));
+            } else {
+                rate_limited
+            },
+            authentication: if authentication.is_empty() {
+                return Err(missing_field("authentication"));
+            } else {
+                authentication
+            },
         })
     }
 }
@@ -139,12 +160,21 @@ enum FieldValue {
     Method(Ident),
     Name(LitStr),
     Path(LitStr),
-    RateLimited(LitBool),
-    Authentication(Ident),
+    RateLimited(LitBool, Vec<Attribute>),
+    Authentication(Ident, Vec<Attribute>),
 }
 
 impl Parse for FieldValue {
     fn parse(input: ParseStream) -> syn::Result<Self> {
+        let attrs: Vec<Attribute> = input.call(Attribute::parse_outer)?;
+        for attr in attrs.iter() {
+            if !util::is_cfg_attribute(attr) {
+                return Err(syn::Error::new_spanned(
+                    &attr,
+                    "only `cfg` attributes may appear here",
+                ));
+            }
+        }
         let field: Field = input.parse()?;
         let _: Token![:] = input.parse()?;
 
@@ -164,8 +194,8 @@ impl Parse for FieldValue {
 
                 Self::Path(path)
             }
-            Field::RateLimited => Self::RateLimited(input.parse()?),
-            Field::Authentication => Self::Authentication(input.parse()?),
+            Field::RateLimited => Self::RateLimited(input.parse()?, attrs),
+            Field::Authentication => Self::Authentication(input.parse()?, attrs),
         })
     }
 }

ruma-api-macros/src/util.rs

@@ -5,7 +5,7 @@ use proc_macro_crate::crate_name;
 use quote::quote;
 use std::collections::BTreeSet;
 use syn::{
-    AngleBracketedGenericArguments, GenericArgument, Ident, Lifetime,
+    AngleBracketedGenericArguments, AttrStyle, Attribute, GenericArgument, Ident, Lifetime,
     ParenthesizedGenericArguments, PathArguments, Type, TypeArray, TypeBareFn, TypeGroup,
     TypeParen, TypePath, TypePtr, TypeReference, TypeSlice, TypeTuple,
 };
@@ -402,3 +402,7 @@ pub fn import_ruma_api() -> TokenStream {
         quote! { ::ruma_api }
     }
 }
+
+pub(crate) fn is_cfg_attribute(attr: &Attribute) -> bool {
+    attr.style == AttrStyle::Outer && attr.path.is_ident("cfg")
+}

ruma-api/tests/ruma_api_macros.rs

@@ -9,7 +9,15 @@ pub mod some_endpoint {
             method: POST, // An `http::Method` constant. No imports required.
             name: "some_endpoint",
             path: "/_matrix/some/endpoint/:baz",
+
+            #[cfg(all())]
+            rate_limited: true,
+            #[cfg(any())]
             rate_limited: false,
+
+            #[cfg(all())]
+            authentication: AccessToken,
+            #[cfg(any())]
             authentication: None,
         }