Fix negative enums in protobuf not serializing & de-serializing (#2400)

From language guide: Enumerator constants must be in the range of a 32-bit integer. Since enum values use varint encoding on the wire, negative values are inefficient and thus not recommended (but still possible).
Kotlin · Aug 14, 2023 · a7109d8 · a7109d8
1 parent 1e88d42
commit a7109d8
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Showing 3 changed files with 4 additions and 3 deletions.
diff --git a/formats/protobuf/commonMain/src/kotlinx/serialization/protobuf/internal/ProtobufDecoding.kt b/formats/protobuf/commonMain/src/kotlinx/serialization/protobuf/internal/ProtobufDecoding.kt
@@ -80,7 +80,7 @@ internal open class ProtobufDecoder(
 
  private fun findIndexByTag(descriptor: SerialDescriptor, protoTag: Int): Int {
  // Fast-path: tags are incremental, 1-based
- if (protoTag < descriptor.elementsCount) {
+ if (protoTag < descriptor.elementsCount && protoTag >= 0) {
  val protoId = extractProtoId(descriptor, protoTag, true)
  if (protoId == protoTag) return protoTag
  }

diff --git a/formats/protobuf/jvmTest/src/kotlinx/serialization/protobuf/RandomTests.kt b/formats/protobuf/jvmTest/src/kotlinx/serialization/protobuf/RandomTests.kt
@@ -162,11 +162,11 @@ class RandomTest : ShouldSpec() {
  }
  }
 
- enum class KCoffee { AMERICANO, LATTE, CAPPUCCINO }
+ enum class KCoffee(val value: Int) { AMERICANO(0), LATTE(1), CAPPUCCINO(2), @ProtoNumber(-1) NO_COFFEE(-1) }
 
  @Serializable
  data class KTestEnum(@ProtoNumber(1) val a: KCoffee): IMessage {
- override fun toProtobufMessage() = TestEnum.newBuilder().setA(TestEnum.Coffee.forNumber(a.ordinal)).build()
+ override fun toProtobufMessage() = TestEnum.newBuilder().setA(TestEnum.Coffee.forNumber(a.value)).build()
 
  companion object : Gen<KTestEnum> {
  override fun generate(): KTestEnum = KTestEnum(Gen.oneOf<KCoffee>().generate())

diff --git a/formats/protobuf/testProto/test_data.proto b/formats/protobuf/testProto/test_data.proto
@@ -59,6 +59,7 @@ message TestEnum {
  Americano = 0;
  Latte = 1;
  Capuccino = 2;
+ NoCoffee = -1;
  }
  required Coffee a = 1;
 }