Omit params field from requests instead of sending null value

core/src/types/params.rs

@@ -36,6 +36,11 @@ impl Params {
 			p => Err(Error::invalid_params_with_details("No parameters were expected", p)),
 		}
 	}
+
+	/// Check for None
+	pub fn is_none(&self) -> bool {
+		matches!(*self, Params::None)
+	}
 }
 
 impl From<Params> for Value {
@@ -110,4 +115,12 @@ mod tests {
 		let params: (u64,) = Params::Array(vec![Value::from(1)]).parse().unwrap();
 		assert_eq!(params, (1,));
 	}
+
+	#[test]
+	fn detect_none() {
+		let none = Params::None;
+		assert!(none.is_none());
+		let some = Params::Array(vec![]);
+		assert!(!some.is_none());
+	}
 }

core/src/types/request.rs

@@ -12,7 +12,7 @@ pub struct MethodCall {
 	pub method: String,
 	/// A Structured value that holds the parameter values to be used
 	/// during the invocation of the method. This member MAY be omitted.
-	#[serde(default = "default_params")]
+	#[serde(default = "default_params", skip_serializing_if = "Params::is_none")]
 	pub params: Params,
 	/// An identifier established by the Client that MUST contain a String,
 	/// Number, or NULL value if included. If it is not included it is assumed
@@ -105,6 +105,21 @@ mod tests {
 		);
 	}
 
+	#[test]
+	fn call_serizalize_without_params() {
+		use serde_json;
+
+		let m = MethodCall {
+			jsonrpc: Some(Version::V2),
+			method: "status".to_owned(),
+			params: Params::None,
+			id: Id::Num(1),
+		};
+
+		let serialized = serde_json::to_string(&m).unwrap();
+		assert_eq!(serialized, r#"{"jsonrpc":"2.0","method":"status","id":1}"#);
+	}
+
 	#[test]
 	fn notification_serialize() {
 		use serde_json;