Implement server side named parameters

Author: Lucas Ransan

derive/src/options.rs

@@ -62,10 +62,7 @@ impl DeriveOptions {
 			options.enable_client = true;
 			options.enable_server = true;
 		}
-		if options.enable_server && options.params_style == ParamStyle::Named {
-			// This is not allowed at this time
-			panic!("Server code generation only supports `params = \"positional\"` (default) or `params = \"raw\" at this time.")
-		}
+
 		Ok(options)
 	}
 }

derive/src/rpc_trait.rs

@@ -1,5 +1,4 @@
 use crate::options::DeriveOptions;
-use crate::params_style::ParamStyle;
 use crate::rpc_attr::{AttributeKind, PubSubMethodKind, RpcMethodAttribute};
 use crate::to_client::generate_client_module;
 use crate::to_delegate::{generate_trait_item_method, MethodRegistration, RpcMethod};
@@ -22,10 +21,6 @@ const MISSING_UNSUBSCRIBE_METHOD_ERR: &str =
 	"Can't find unsubscribe method, expected a method annotated with `unsubscribe` \
 	 e.g. `#[pubsub(subscription = \"hello\", unsubscribe, name = \"hello_unsubscribe\")]`";
 
-pub const USING_NAMED_PARAMS_WITH_SERVER_ERR: &str =
-	"`params = \"named\"` can only be used to generate a client (on a trait annotated with #[rpc(client)]). \
-	 At this time the server does not support named parameters.";
-
 const RPC_MOD_NAME_PREFIX: &str = "rpc_impl_";
 
 struct RpcTrait {
@@ -222,12 +217,6 @@ fn rpc_wrapper_mod_name(rpc_trait: &syn::ItemTrait) -> syn::Ident {
 	syn::Ident::new(&mod_name, proc_macro2::Span::call_site())
 }
 
-fn has_named_params(methods: &[RpcMethod]) -> bool {
-	methods
-		.iter()
-		.any(|method| method.attr.params_style == Some(ParamStyle::Named))
-}
-
 pub fn crate_name(name: &str) -> Result<Ident> {
 	proc_macro_crate::crate_name(name)
 		.map(|name| Ident::new(&name, Span::call_site()))
@@ -264,9 +253,6 @@ pub fn rpc_impl(input: syn::Item, options: &DeriveOptions) -> Result<proc_macro2
 		});
 	}
 	if options.enable_server {
-		if has_named_params(&methods) {
-			return Err(syn::Error::new_spanned(rpc_trait, USING_NAMED_PARAMS_WITH_SERVER_ERR));
-		}
 		let rpc_server_module = generate_server_module(&method_registrations, &rpc_trait, &methods)?;
 		submodules.push(rpc_server_module);
 		exports.push(quote! {

derive/src/to_delegate.rs

@@ -218,6 +218,21 @@ impl RpcMethod {
 			})
 			.collect();
 
+		let arg_names: Vec<_> = self
+			.trait_item
+			.sig
+			.inputs
+			.iter()
+			.cloned()
+			.filter_map(|arg| match arg {
+				syn::FnArg::Typed(pat) => match *pat.pat {
+					syn::Pat::Ident(pat) => Some(pat.ident),
+					_ => None,
+				},
+				_ => None,
+			})
+			.collect();
+
 		// special args are those which are not passed directly via rpc params: metadata, subscriber
 		let special_args = Self::special_args(&param_types);
 		param_types.retain(|ty| !special_args.iter().any(|(_, sty)| sty == ty));
@@ -246,7 +261,17 @@ impl RpcMethod {
 			} else if self.attr.params_style == Some(ParamStyle::Positional) {
 				quote! { let params = params.parse::<(#(#param_types, )*)>(); }
 			} else {
-				unimplemented!("Server side named parameters are not implemented");
+				quote! {
+					#[derive(serde::Deserialize)]
+					#[allow(non_camel_case_types)]
+					struct __Params {
+						#(
+							#arg_names: #param_types,
+						)*
+					}
+					let params = params.parse::<__Params>()
+						.map(|__Params { #(#arg_names, )* }| (#(#arg_names, )*));
+				}
 			}
 		};
 

derive/tests/macros.rs

@@ -30,6 +30,9 @@ pub trait Rpc {
 	#[rpc(name = "raw", params = "raw")]
 	fn raw(&self, params: Params) -> Result<String>;
 
+	#[rpc(name = "named_add", params = "named")]
+	fn named_add(&self, a: u64, b: u64) -> Result<u64>;
+
 	/// Handles a notification.
 	#[rpc(name = "notify")]
 	fn notify(&self, a: u64);
@@ -55,6 +58,10 @@ impl Rpc for RpcImpl {
 		Ok("OK".into())
 	}
 
+	fn named_add(&self, a: u64, b: u64) -> Result<u64> {
+		Ok(a + b)
+	}
+
 	fn notify(&self, a: u64) {
 		println!("Received `notify` with value: {}", a);
 	}
@@ -222,6 +229,34 @@ fn should_accept_any_raw_params() {
 	assert_eq!(expected, result4);
 }
 
+#[test]
+fn should_accept_named_params() {
+	let mut io = IoHandler::new();
+	let rpc = RpcImpl::default();
+	io.extend_with(rpc.to_delegate());
+
+	// when
+	let req1 = r#"{"jsonrpc":"2.0","id":1,"method":"named_add","params":{"a":1,"b":2}}"#;
+	let req2 = r#"{"jsonrpc":"2.0","id":1,"method":"named_add","params":{"b":2,"a":1}}"#;
+
+	let res1 = io.handle_request_sync(req1);
+	let res2 = io.handle_request_sync(req2);
+
+	let expected = r#"{
+	    "jsonrpc": "2.0",
+		"result": 3,
+		"id": 1
+    }"#;
+	let expected: Response = serde_json::from_str(expected).unwrap();
+
+	// then
+	let result1: Response = serde_json::from_str(&res1.unwrap()).unwrap();
+	assert_eq!(expected, result1);
+
+	let result2: Response = serde_json::from_str(&res2.unwrap()).unwrap();
+	assert_eq!(expected, result2);
+}
+
 #[test]
 fn should_accept_only_notifications() {
 	let mut io = IoHandler::new();