Add a method to handle empty response. (paritytech#473)

core/src/io.rs

@@ -529,6 +529,24 @@ mod tests {
 		assert_eq!(called.load(atomic::Ordering::SeqCst), true);
 	}
 
+	#[test]
+	fn test_batch_notification() {
+		use std::sync::atomic;
+		use std::sync::Arc;
+
+		let mut io = IoHandler::new();
+
+		let called = Arc::new(atomic::AtomicBool::new(false));
+		let c = called.clone();
+		io.add_notification("say_hello", move |_| {
+			c.store(true, atomic::Ordering::SeqCst);
+		});
+
+		let request = r#"[{"jsonrpc": "2.0", "method": "say_hello", "params": [42, 23]}]"#;
+		assert_eq!(io.handle_request_sync(request), None);
+		assert_eq!(called.load(atomic::Ordering::SeqCst), true);
+	}
+
 	#[test]
 	fn test_send_sync() {
 		fn is_send_sync<T>(_obj: T) -> bool

core/src/types/response.rs

@@ -105,6 +105,17 @@ impl Response {
 		}
 		.into()
 	}
+
+	/// Deserialize `Response` from given JSON string.
+	///
+	/// This method will handle an empty string as empty batch response.
+	pub fn from_json(s: &str) -> Result<Self, serde_json::Error> {
+		if s.is_empty() {
+			Ok(Response::Batch(vec![]))
+		} else {
+			serde_json::from_str(s)
+		}
+	}
 }
 
 impl From<Failure> for Response {
@@ -268,3 +279,15 @@ fn handle_incorrect_responses() {
 		"Expected error when deserializing invalid payload."
 	);
 }
+
+#[test]
+fn should_parse_empty_response_as_batch() {
+	use serde_json;
+
+	let dsr = r#""#;
+
+	let deserialized1: Result<Response, _>= serde_json::from_str(dsr);
+	let deserialized2: Result<Response, _> = Response::from_json(dsr);
+	assert!(deserialized1.is_err(), "Empty string is not valid JSON, so we should get an error.");
+	assert_eq!(deserialized2.unwrap(), Response::Batch(vec![]));
+}