server: Expose the subscription ID (#900)

* server: Expose the subscription ID

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* tests: Check subscription ID is exposed correctly

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* server: Dedicated method for exposing the sub ID

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Fix clippy

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

core/src/server/rpc_module.rs

@@ -873,6 +873,18 @@ impl SubscriptionSink {
 		}
 	}
 
+	/// Return the subscription ID if the the subscription was accepted.
+	///
+	/// [`SubscriptionSink::accept`] should be called prior to this method.
+	pub fn subscription_id(&self) -> Option<RpcSubscriptionId<'static>> {
+		if self.id.is_some() {
+			// Subscription was not accepted.
+			None
+		} else {
+			Some(self.uniq_sub.sub_id.clone())
+		}
+	}
+
 	/// Send a message back to subscribers.
 	///
 	/// Returns

server/src/tests/ws.rs

@@ -490,8 +490,7 @@ async fn can_register_modules() {
 
 	assert_eq!(mod1.method_names().count(), 2);
 	let err = mod1.merge(mod2).unwrap_err();
-	let _expected_err = Error::MethodAlreadyRegistered(String::from("bla"));
-	assert!(matches!(err, _expected_err));
+	assert!(matches!(err, Error::MethodAlreadyRegistered(err) if err == "bla"));
 	assert_eq!(mod1.method_names().count(), 2);
 }
 
@@ -548,8 +547,15 @@ async fn custom_subscription_id_works() {
 	let mut module = RpcModule::new(());
 	module
 		.register_subscription("subscribe_hello", "subscribe_hello", "unsubscribe_hello", |_, mut sink, _| {
+			// There is no subscription ID prior to calling accept.
+			let sub_id = sink.subscription_id();
+			assert!(sub_id.is_none());
+
 			sink.accept()?;
 
+			let sub_id = sink.subscription_id();
+			assert!(matches!(sub_id, Some(SubscriptionId::Str(id)) if id == "0xdeadbeef"));
+
 			tokio::spawn(async move {
 				loop {
 					let _ = &sink;

tests/tests/rpc_module.rs

@@ -416,7 +416,7 @@ async fn accepted_twice_subscription_without_server() {
 	module
 		.register_subscription("my_sub", "my_sub", "my_unsub", |_, mut sink, _| {
 			let res = sink.accept();
-			assert!(matches!(res, Ok(())));
+			assert!(matches!(res, Ok(_)));
 
 			let res = sink.accept();
 			assert!(matches!(res, Err(_)));