Fix RawMessage decoder

Author: ghostbuster91

modules/core/src/main/scala/jsonrpclib/internals/RawMessage.scala

@@ -84,9 +84,10 @@ private[jsonrpclib] object RawMessage {
       error <- c.downField("error").as[Option[ErrorPayload]]
       id <- c.downField("id").as[Option[CallId]]
       resultOpt <-
-        if (c.downField("result").succeeded)
-          c.downField("result").as[Option[Payload]].map(res => Some(res))
-        else Right(None)
+        c.downField("result")
+          .success
+          .map(_.as[Option[Payload]].map(Some(_)))
+          .getOrElse(Right(None))
     } yield RawMessage(jsonrpc, method, resultOpt, error, params, id)
   }
 }

modules/core/src/test/scala/jsonrpclib/RawMessageSpec.scala

@@ -57,6 +57,15 @@ object RawMessageSpec extends FunSuite {
     assert(result == expected, s"Expected: $expected, got: $result")
   }
 
+  test("response message serialization with nested results") {
+    val input: Message =
+      OutputMessage.ResponseMessage(CallId.NumberId(1), Payload(Json.obj("result" -> Json.fromInt(1))))
+    val expected = """{"jsonrpc":"2.0","id":1,"result":{"result":1}}"""
+    val result = writeToString(input.asJson)
+
+    assert(result == expected, s"Expected: $expected, got: $result")
+  }
+
   test("error message serialization") {
     val input: Message = OutputMessage.ErrorMessage(
       CallId.NumberId(1),