Accept also None or Objects as params

according to the jsonrpc spec params can be missing, or an object too

src/client.rs

@@ -49,7 +49,11 @@ impl Client {
     ///
     /// To construct the arguments, one can use one of the shorthand methods
     /// [`crate::arg`] or [`crate::try_arg`].
-    pub fn build_request<'a>(&self, method: &'a str, params: &'a [Box<RawValue>]) -> Request<'a> {
+    pub fn build_request<'a>(
+        &self,
+        method: &'a str,
+        params: Option<&'a Box<RawValue>>,
+    ) -> Request<'a> {
         let nonce = self.nonce.fetch_add(1, atomic::Ordering::Relaxed);
         Request {
             method,
@@ -115,7 +119,7 @@ impl Client {
     pub fn call<R: for<'a> serde::de::Deserialize<'a>>(
         &self,
         method: &str,
-        args: &[Box<RawValue>],
+        args: Option<&Box<RawValue>>,
     ) -> Result<R, Error> {
         let request = self.build_request(method, args);
         let id = request.id.clone();
@@ -224,9 +228,9 @@ mod tests {
     fn sanity() {
         let client = Client::with_transport(DummyTransport);
         assert_eq!(client.nonce.load(sync::atomic::Ordering::Relaxed), 1);
-        let req1 = client.build_request("test", &[]);
+        let req1 = client.build_request("test", None);
         assert_eq!(client.nonce.load(sync::atomic::Ordering::Relaxed), 2);
-        let req2 = client.build_request("test", &[]);
+        let req2 = client.build_request("test", None);
         assert_eq!(client.nonce.load(sync::atomic::Ordering::Relaxed), 3);
         assert!(req1.id != req2.id);
     }

src/http/simple_http.rs

@@ -818,11 +818,11 @@ mod tests {
         let port = rx.recv().unwrap();
         let client =
             Client::simple_http(format!("localhost:{}", port).as_str(), None, None).unwrap();
-        let request = client.build_request("test_request", &[]);
+        let request = client.build_request("test_request", None);
         let result = client.send_request(request).unwrap();
         assert_eq!(result.id, Value::Number(Number::from(0)));
         thread::sleep(Duration::from_secs(1));
-        let request = client.build_request("test_request2", &[]);
+        let request = client.build_request("test_request2", None);
         let result2 = client.send_request(request)
             .expect("This second request should not be an Err like `Err(Transport(HttpResponseTooShort { actual: 0, needed: 12 }))`");
         assert_eq!(result2.id, Value::Number(Number::from(1)));

src/lib.rs

@@ -70,7 +70,7 @@ pub struct Request<'a> {
     /// The name of the RPC call.
     pub method: &'a str,
     /// Parameters to the RPC call.
-    pub params: &'a [Box<RawValue>],
+    pub params: Option<&'a Box<RawValue>>,
     /// Identifier for this request, which should appear in the response.
     pub id: serde_json::Value,
     /// jsonrpc field, MUST be "2.0".

src/simple_tcp.rs

@@ -134,7 +134,7 @@ mod tests {
         let addr = server.local_addr().unwrap();
         let dummy_req = Request {
             method: "arandommethod",
-            params: &[],
+            params: None,
             id: serde_json::Value::Number(4242242.into()),
             jsonrpc: Some("2.0"),
         };