fix(proc macros): subscriptions must return result (#455)

Similar to #435 that adds the same restrictions to subscriptions too.
To avoid having faulty trait bounds on when the subcription actually returns Result.

examples/proc_macro.rs

@@ -46,7 +46,7 @@ where
 
 	/// Subscription that takes a `StorageKey` as input and produces a `Vec<Hash>`.
 	#[subscription(name = "subscribeStorage", item = Vec<Hash>)]
-	fn subscribe_storage(&self, keys: Option<Vec<StorageKey>>);
+	fn subscribe_storage(&self, keys: Option<Vec<StorageKey>>) -> Result<(), Error>;
 }
 
 pub struct RpcServerImpl;
@@ -61,8 +61,12 @@ impl RpcServer<ExampleHash, ExampleStorageKey> for RpcServerImpl {
 		Ok(vec![storage_key])
 	}
 
-	fn subscribe_storage(&self, mut sink: SubscriptionSink, _keys: Option<Vec<ExampleStorageKey>>) {
-		sink.send(&vec![[0; 32]]).unwrap();
+	fn subscribe_storage(
+		&self,
+		mut sink: SubscriptionSink,
+		_keys: Option<Vec<ExampleStorageKey>>,
+	) -> Result<(), Error> {
+		sink.send(&vec![[0; 32]])
 	}
 }
 

proc-macros/src/helpers.rs

@@ -78,7 +78,7 @@ fn find_jsonrpsee_crate(http_name: &str, ws_name: &str) -> Result<proc_macro2::T
 ///    fn call(&self, a: A) -> JsonRpcResult<B>;
 ///
 ///    #[subscription(name = "sub", item = Vec<C>)]
-///    fn sub(&self);
+///    fn sub(&self) -> JsonRpcResult<()>;
 ///  }
 /// ```
 ///

proc-macros/src/lib.rs

@@ -215,7 +215,7 @@ pub(crate) mod visitor;
 ///         fn sync_method(&self) -> JsonRpcResult<u16>;
 ///
 ///         #[subscription(name = "sub", item = String)]
-///         fn sub(&self);
+///         fn sub(&self) -> JsonRpcResult<()>;
 ///     }
 ///
 ///     // Structure that will implement the `MyRpcServer` trait.
@@ -236,9 +236,9 @@ pub(crate) mod visitor;
 ///         // We could've spawned a `tokio` future that yields values while our program works,
 ///         // but for simplicity of the example we will only send two values and then close
 ///         // the subscription.
-///         fn sub(&self, mut sink: SubscriptionSink) {
-///             sink.send(&"Response_A").unwrap();
-///             sink.send(&"Response_B").unwrap();
+///         fn sub(&self, mut sink: SubscriptionSink) -> JsonRpcResult<()> {
+///             sink.send(&"Response_A")?;
+///             sink.send(&"Response_B")
 ///         }
 ///     }
 /// }

proc-macros/src/render_server.rs

@@ -168,7 +168,7 @@ impl RpcDescription {
 				handle_register_result(quote! {
 					rpc.register_subscription(#rpc_sub_name, #rpc_unsub_name, |params, sink, context| {
 						#parsing
-						Ok(context.as_ref().#rust_method_name(sink, #params_seq))
+						context.as_ref().#rust_method_name(sink, #params_seq)
 					})
 				})
 			})

proc-macros/src/rpc_macro.rs

@@ -180,9 +180,6 @@ impl RpcDescription {
 					if method.sig.asyncness.is_some() {
 						return Err(syn::Error::new_spanned(&method, "Subscription methods must not be `async`"));
 					}
-					if !matches!(method.sig.output, syn::ReturnType::Default) {
-						return Err(syn::Error::new_spanned(&method, "Subscription methods must not return anything"));
-					}
 
 					let sub_data = RpcSubscription::from_item(method.clone())?;
 					subscriptions.push(sub_data);

proc-macros/tests/ui/correct/alias_doesnt_use_namespace.rs

@@ -7,7 +7,7 @@ pub trait Rpc {
 	async fn async_method(&self, param_a: u8, param_b: String) -> JsonRpcResult<u16>;
 
 	#[subscription(name = "getFood", item = String, aliases = "getFood", unsubscribe_aliases = "unsubscribegetFood")]
-	fn sub(&self);
+	fn sub(&self) -> JsonRpcResult<()>;
 }
 
 fn main() {}

proc-macros/tests/ui/correct/basic.rs

@@ -26,10 +26,10 @@ pub trait Rpc {
 	fn sync_method(&self) -> JsonRpcResult<u16>;
 
 	#[subscription(name = "sub", item = String)]
-	fn sub(&self);
+	fn sub(&self) -> JsonRpcResult<()>;
 
 	#[subscription(name = "echo", aliases = "ECHO", item = u32, unsubscribe_aliases = "NotInterested, listenNoMore")]
-	fn sub_with_params(&self, val: u32);
+	fn sub_with_params(&self, val: u32) -> JsonRpcResult<()>;
 }
 
 pub struct RpcServerImpl;
@@ -58,14 +58,14 @@ impl RpcServer for RpcServerImpl {
 		Ok(10u16)
 	}
 
-	fn sub(&self, mut sink: SubscriptionSink) {
-		sink.send(&"Response_A").unwrap();
-		sink.send(&"Response_B").unwrap();
+	fn sub(&self, mut sink: SubscriptionSink) -> JsonRpcResult<()> {
+		sink.send(&"Response_A")?;
+		sink.send(&"Response_B")
 	}
 
-	fn sub_with_params(&self, mut sink: SubscriptionSink, val: u32) {
-		sink.send(&val).unwrap();
-		sink.send(&val).unwrap();
+	fn sub_with_params(&self, mut sink: SubscriptionSink, val: u32) -> JsonRpcResult<()> {
+		sink.send(&val)?;
+		sink.send(&val)
 	}
 }
 

proc-macros/tests/ui/correct/only_server.rs

@@ -14,7 +14,7 @@ pub trait Rpc {
 	fn sync_method(&self) -> JsonRpcResult<u16>;
 
 	#[subscription(name = "sub", item = String)]
-	fn sub(&self);
+	fn sub(&self) -> JsonRpcResult<()>;
 }
 
 pub struct RpcServerImpl;
@@ -29,9 +29,9 @@ impl RpcServer for RpcServerImpl {
 		Ok(10u16)
 	}
 
-	fn sub(&self, mut sink: SubscriptionSink) {
-		sink.send(&"Response_A").unwrap();
-		sink.send(&"Response_B").unwrap();
+	fn sub(&self, mut sink: SubscriptionSink) -> JsonRpcResult<()> {
+		sink.send(&"Response_A")?;
+		sink.send(&"Response_B")
 	}
 }
 

proc-macros/tests/ui/correct/rpc_deny_missing_docs.rs

@@ -12,7 +12,7 @@ pub trait ApiWithoutDocumentation {
 
 	/// Subscription docs.
 	#[subscription(name = "sub", item = String)]
-	fn sub(&self);
+	fn sub(&self) -> jsonrpsee::types::JsonRpcResult<()>;
 }
 
 fn main() {}

proc-macros/tests/ui/incorrect/sub/sub_conflicting_alias.rs

@@ -1,9 +1,9 @@
-use jsonrpsee::proc_macros::rpc;
+use jsonrpsee::{proc_macros::rpc, types::JsonRpcResult};
 
 #[rpc(client, server)]
 pub trait DuplicatedSubAlias {
 	#[subscription(name = "alias", item = String, aliases = "hello_is_goodbye", unsubscribe_aliases = "hello_is_goodbye")]
-	fn async_method(&self);
+	fn async_method(&self) -> JsonRpcResult<()>;
 }
 
 fn main() {}

proc-macros/tests/ui/incorrect/sub/sub_conflicting_alias.stderr

@@ -1,5 +1,5 @@
 error: "hello_is_goodbye" is already defined
  --> $DIR/sub_conflicting_alias.rs:6:5
   |
-6 |     fn async_method(&self);
+6 |     fn async_method(&self) -> JsonRpcResult<()>;
   |        ^^^^^^^^^^^^

tests/tests/proc_macros.rs

@@ -48,10 +48,10 @@ mod rpc_impl {
 		fn sync_method(&self) -> JsonRpcResult<u16>;
 
 		#[subscription(name = "sub", item = String)]
-		fn sub(&self);
+		fn sub(&self) -> JsonRpcResult<()>;
 
 		#[subscription(name = "echo", aliases = "alias_echo", item = u32)]
-		fn sub_with_params(&self, val: u32);
+		fn sub_with_params(&self, val: u32) -> JsonRpcResult<()>;
 
 		#[method(name = "params")]
 		fn params(&self, a: u8, b: &str) -> JsonRpcResult<String> {
@@ -102,7 +102,7 @@ mod rpc_impl {
 
 		/// All head subscription
 		#[subscription(name = "subscribeAllHeads", item = Header)]
-		fn subscribe_all_heads(&self, hash: Hash);
+		fn subscribe_all_heads(&self, hash: Hash) -> JsonRpcResult<()>;
 	}
 
 	/// Trait to ensure that the trait bounds are correct.
@@ -117,7 +117,7 @@ mod rpc_impl {
 	pub trait OnlyGenericSubscription<Input, R> {
 		/// Get header of a relay chain block.
 		#[subscription(name = "sub", item = Vec<R>)]
-		fn sub(&self, hash: Input);
+		fn sub(&self, hash: Input) -> JsonRpcResult<()>;
 	}
 
 	/// Trait to ensure that the trait bounds are correct.
@@ -154,14 +154,16 @@ mod rpc_impl {
 			Ok(10u16)
 		}
 
-		fn sub(&self, mut sink: SubscriptionSink) {
-			sink.send(&"Response_A").unwrap();
-			sink.send(&"Response_B").unwrap();
+		fn sub(&self, mut sink: SubscriptionSink) -> JsonRpcResult<()> {
+			sink.send(&"Response_A")?;
+			sink.send(&"Response_B")?;
+			Ok(())
 		}
 
-		fn sub_with_params(&self, mut sink: SubscriptionSink, val: u32) {
-			sink.send(&val).unwrap();
-			sink.send(&val).unwrap();
+		fn sub_with_params(&self, mut sink: SubscriptionSink, val: u32) -> JsonRpcResult<()> {
+			sink.send(&val)?;
+			sink.send(&val)?;
+			Ok(())
 		}
 	}
 
@@ -174,8 +176,8 @@ mod rpc_impl {
 
 	#[async_trait]
 	impl OnlyGenericSubscriptionServer<String, String> for RpcServerImpl {
-		fn sub(&self, mut sink: SubscriptionSink, _: String) {
-			sink.send(&"hello").unwrap();
+		fn sub(&self, mut sink: SubscriptionSink, _: String) -> JsonRpcResult<()> {
+			sink.send(&"hello")
 		}
 	}
 }