Fix parsing of responses with null result (#74)

core/src/jsonrpclib/Codec.scala

@@ -16,16 +16,21 @@ object Codec {
   def decode[A](payload: Option[Payload])(implicit codec: Codec[A]): Either[ProtocolError, A] = codec.decode(payload)
 
   implicit def fromJsonCodec[A](implicit jsonCodec: JsonValueCodec[A]): Codec[A] = new Codec[A] {
-    def encode(a: A): Payload = Payload(writeToArray(a))
+    def encode(a: A): Payload = {
+      Payload(writeToArray(a))
+    }
 
     def decode(payload: Option[Payload]): Either[ProtocolError, A] = {
       try {
         payload match {
-          case Some(Payload(array)) => Right(readFromArray(array))
-          case None                 => Left(ProtocolError.ParseError("Expected to decode a payload"))
+          case Some(Payload.Data(payload)) => Right(readFromArray(payload))
+          case Some(Payload.NullPayload)   => Right(readFromArray(nullArray))
+          case None                        => Left(ProtocolError.ParseError("Expected to decode a payload"))
         }
       } catch { case e: JsonReaderException => Left(ProtocolError.ParseError(e.getMessage())) }
     }
   }
 
+  private val nullArray = "null".getBytes()
+
 }

core/src/jsonrpclib/Payload.scala

@@ -5,26 +5,45 @@ import com.github.plokhotnyuk.jsoniter_scala.core.JsonValueCodec
 import com.github.plokhotnyuk.jsoniter_scala.core.JsonWriter
 
 import java.util.Base64
+import jsonrpclib.Payload.Data
+import jsonrpclib.Payload.NullPayload
 
-final case class Payload(array: Array[Byte]) {
-  override def equals(other: Any) = other match {
-    case bytes: Payload => java.util.Arrays.equals(array, bytes.array)
-    case _              => false
+sealed trait Payload extends Product with Serializable {
+  def stripNull: Option[Payload.Data] = this match {
+    case d @ Data(_) => Some(d)
+    case NullPayload => None
   }
-
-  override lazy val hashCode: Int = java.util.Arrays.hashCode(array)
-
-  override def toString = Base64.getEncoder.encodeToString(array)
 }
+
 object Payload {
+  def apply(value: Array[Byte]) = {
+    if (value == null) NullPayload
+    else Data(value)
+  }
+  final case class Data(array: Array[Byte]) extends Payload {
+    override def equals(other: Any) = other match {
+      case bytes: Data => java.util.Arrays.equals(array, bytes.array)
+      case _           => false
+    }
+
+    override lazy val hashCode: Int = java.util.Arrays.hashCode(array)
+
+    override def toString = Base64.getEncoder.encodeToString(array)
+  }
+
+  case object NullPayload extends Payload
 
   implicit val payloadJsonValueCodec: JsonValueCodec[Payload] = new JsonValueCodec[Payload] {
     def decodeValue(in: JsonReader, default: Payload): Payload = {
-      Payload(in.readRawValAsBytes())
+      Data(in.readRawValAsBytes())
     }
 
     def encodeValue(bytes: Payload, out: JsonWriter): Unit =
-      out.writeRawVal(bytes.array)
+      bytes match {
+        case Data(array) => out.writeRawVal(array)
+        case NullPayload => out.writeNull()
+
+      }
 
     def nullValue: Payload = null
   }

core/src/jsonrpclib/internals/RawMessage.scala

@@ -3,11 +3,12 @@ package internals
 
 import com.github.plokhotnyuk.jsoniter_scala.core._
 import com.github.plokhotnyuk.jsoniter_scala.macros.JsonCodecMaker
+import com.github.plokhotnyuk.jsoniter_scala.macros.CodecMakerConfig
 
 private[jsonrpclib] case class RawMessage(
     jsonrpc: String,
     method: Option[String] = None,
-    result: Option[Payload] = None,
+    result: Option[Option[Payload]] = None,
     error: Option[ErrorPayload] = None,
     params: Option[Payload] = None,
     id: Option[CallId] = None
@@ -21,7 +22,7 @@ private[jsonrpclib] case class RawMessage(
     case (Some(callId), None) =>
       (error, result) match {
         case (Some(error), _) => Right(OutputMessage.ErrorMessage(callId, error))
-        case (_, Some(data))  => Right(OutputMessage.ResponseMessage(callId, data))
+        case (_, Some(data))  => Right(OutputMessage.ResponseMessage(callId, data.getOrElse(Payload.NullPayload)))
         case (None, None) =>
           Left(
             ProtocolError.InvalidRequest(
@@ -48,10 +49,11 @@ private[jsonrpclib] object RawMessage {
       RawMessage(`2.0`, method = Some(method), params = params, id = Some(callId))
     case OutputMessage.ErrorMessage(callId, errorPayload) =>
       RawMessage(`2.0`, error = Some(errorPayload), id = Some(callId))
-    case OutputMessage.ResponseMessage(callId, data) => RawMessage(`2.0`, result = Some(data), id = Some(callId))
+    case OutputMessage.ResponseMessage(callId, data) =>
+      RawMessage(`2.0`, result = Some(data.stripNull), id = Some(callId))
   }
 
   implicit val rawMessageJsonValueCodecs: JsonValueCodec[RawMessage] =
-    JsonCodecMaker.make
+    JsonCodecMaker.make(CodecMakerConfig.withSkipNestedOptionValues(true))
 
 }

core/test/src-jvm-native/jsonrpclib/RawMessageSpec.scala

@@ -0,0 +1,30 @@
+package jsonrpclib
+
+import munit._
+import com.github.plokhotnyuk.jsoniter_scala.core._
+import internals._
+import jsonrpclib.CallId.NumberId
+import jsonrpclib.OutputMessage.ResponseMessage
+
+class RawMessageSpec() extends FunSuite {
+  test("json parsing with null result") {
+    // This is a perfectly valid response object, as result field has to be present,
+    // but can be null: https://www.jsonrpc.org/specification#response_object
+    val rawMessage = readFromString[RawMessage](""" {"jsonrpc":"2.0","result":null,"id":3} """.trim)
+    assertEquals(
+      rawMessage,
+      RawMessage(jsonrpc = "2.0", result = Some(None), id = Some(NumberId(3)))
+    )
+
+    assertEquals(rawMessage.toMessage, Right(ResponseMessage(NumberId(3), Payload.NullPayload)))
+
+    // This, on the other hand, is an invalid response message, as result field is missing
+    val invalidRawMessage = readFromString[RawMessage](""" {"jsonrpc":"2.0","id":3} """.trim)
+    assertEquals(
+      invalidRawMessage,
+      RawMessage(jsonrpc = "2.0", result = None, id = Some(NumberId(3)))
+    )
+
+    assert(invalidRawMessage.toMessage.isLeft, invalidRawMessage.toMessage)
+  }
+}

fs2/src/jsonrpclib/fs2/lsp.scala

@@ -12,6 +12,8 @@ import java.nio.charset.Charset
 import java.nio.charset.StandardCharsets
 import jsonrpclib.Message
 import jsonrpclib.ProtocolError
+import jsonrpclib.Payload.Data
+import jsonrpclib.Payload.NullPayload
 
 object lsp {
 
@@ -42,11 +44,15 @@ object lsp {
       }
 
   private def writeChunk(payload: Payload): Chunk[Byte] = {
-    val size = payload.array.size
-    val header = s"Content-Length: ${size}" + "\r\n" * 2
-    Chunk.array(header.getBytes()) ++ Chunk.array(payload.array)
+    val bytes = payload match {
+      case Data(array) => array
+      case NullPayload => nullArray
+    }
+    val header = s"Content-Length: ${bytes.size}" + "\r\n" * 2
+    Chunk.array(header.getBytes()) ++ Chunk.array(bytes)
   }
 
+  private val nullArray = "null".getBytes()
   private val returnByte = '\r'.toByte
   private val newlineByte = '\n'.toByte