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pb: Add MARSHALLER and DESCRIPTOR object to group messages #589

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Merged
Jozott00 merged 2 commits into from
Mar 3, 2026
+36 −17
Merged

pb: Add MARSHALLER and DESCRIPTOR object to group messages #589

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f2a7275
pb: Generate MARSHALLER and DESCRIPTOR for group messages
Jozott00 Mar 2, 2026
8f5123a
pb: Address PR comments
Jozott00 Mar 3, 2026
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1 change: 1 addition & 0 deletions protobuf/protobuf-api/build.gradle.kts
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,7 @@ kotlin {

commonTest {
dependencies {
implementation(projects.protobuf.protobufWkt)
implementation(libs.kotlin.test)
implementation(libs.coroutines.test)
}
Expand Down
10 changes: 10 additions & 0 deletions protobuf/protobuf-api/src/commonTest/kotlin/kotlinx/rpc/protobuf/test/ProtosTest.kt
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Expand Up @@ -446,4 +446,14 @@ class ProtosTest {
(decoded.oneOfWithGroup as WithGroups.OneOfWithGroup.Testgroup).value.value
)
}

@Test
fun testGroupAsStandalone() {
val standaloneGroup = WithGroups.FirstGroup {
value = 42u
}

val decoded = encodeDecode(standaloneGroup, marshallerOf<WithGroups.FirstGroup>())
assertEquals(standaloneGroup.value, decoded.value)
}
}
42 changes: 25 additions & 17 deletions ...n/protobuf/src/main/kotlin/kotlinx/rpc/protoc/gen/ModelToProtobufKotlinCommonGenerator.kt
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Expand Up @@ -101,12 +101,9 @@ class ModelToProtobufKotlinCommonGenerator(
private fun CodeGenerator.generatePublicMessage(declaration: MessageDeclaration) {
if (!declaration.isUserFacing) return

val annotations = mutableListOf<ScopedFormattedString>()
if (!declaration.isGroup) {
annotations.add(
FqName.Annotations.GeneratedProtoMessage.scopedAnnotation()
)
}
val annotations = listOf(
FqName.Annotations.GeneratedProtoMessage.scopedAnnotation()
)

generatedMetadata.protoNamesList.add(declaration.name)

Expand Down Expand Up @@ -773,8 +770,6 @@ class ModelToProtobufKotlinCommonGenerator(

private fun CodeGenerator.generateMarshallerObject(declaration: MessageDeclaration) {
if (!declaration.isUserFacing) return
// the MARSHALLER object is not necessary for groups, as they are inlined messages
if (declaration.isGroup) return

clazz(
name = declaration.marshallerObjectName.simpleName,
Expand Down Expand Up @@ -808,8 +803,11 @@ class ModelToProtobufKotlinCommonGenerator(
scope("%T(source).use".scoped(FqName.RpcClasses.WireDecoder)) {
code("val msg = %T()".scoped(declaration.internalClassName))
scope("checkForPlatformDecodeException".scoped(), nlAfterClosed = false) {
// if the message declaration is a group, we must pass null as the
// startGroup tag to indicate that this message is decoded as standalone (like a normal message)
val groupExtraArg = if (declaration.isGroup) ", null" else ""
code(
"%T.decodeWith(msg, it, config as? %T)".scoped(
"%T.decodeWith(msg, it, config as? %T$groupExtraArg)".scoped(
declaration.internalClassName,
FqName.RpcClasses.ProtobufConfig,
)
Expand All @@ -828,7 +826,6 @@ class ModelToProtobufKotlinCommonGenerator(

private fun CodeGenerator.generateDescriptorObject(declaration: MessageDeclaration) {
if (!declaration.isUserFacing) return
if (declaration.isGroup) return

clazz(
name = "DESCRIPTOR",
Expand Down Expand Up @@ -881,8 +878,12 @@ class ModelToProtobufKotlinCommonGenerator(
.scoped(declaration.internalClassName, FqName.RpcClasses.WireDecoder, FqName.RpcClasses.ProtobufConfig)

if (declaration.isGroup) {
// if the message is a group message, the decoder accepts an optional startGroup tag, which indicates
// that the decoding of the message must end with an END_GROUP tag of the same fieldNr.
// if the startGroup tag is null, we treat it like a normal message.
// the argument is not default null, to avoid that we forget to set it when changing the generator.
args = args.merge(FqName.RpcClasses.KTag.scoped()) { start, kTag ->
"$start, startGroup: $kTag"
"$start, startGroup: $kTag?"
}
}

Expand All @@ -895,14 +896,21 @@ class ModelToProtobufKotlinCommonGenerator(
) {
whileBlock("true".scoped()) {
if (declaration.isGroup) {
code(
"val tag = decoder.readTag() ?: throw %T(\"Missing END_GROUP tag for field: \${startGroup.fieldNr}.\")"
.scoped(FqName.RpcClasses.ProtobufDecodingException)
)
scope("val tag = decoder.readTag() ?: run".scoped()) {
// if the startGroup tag is set, we decode the message as an inline group message,
// so in case of the tag being null, we know that the payload is malformed
scope("startGroup?.let".scoped()) {
code("throw %T(\"Missing END_GROUP tag for field: \${startGroup.fieldNr}.\")"
.scoped(FqName.RpcClasses.ProtobufDecodingException))
}
// if the startGroup is null, we decode the message like a normal non-group message,
// so we stop when the tag is null
code("return".scoped())
}
ifBranch(condition = "tag.wireType == %T".scoped(FqName.RpcClasses.WireType_END_GROUP), ifBlock = {
ifBranch(condition = "tag.fieldNr != startGroup.fieldNr".scoped(), ifBlock = {
ifBranch(condition = "tag.fieldNr != startGroup?.fieldNr".scoped(), ifBlock = {
code(
"throw %T(\"Wrong END_GROUP tag. Expected \${startGroup.fieldNr}, got \${tag.fieldNr}.\")"
"throw %T(\"Wrong END_GROUP tag. Expected \${startGroup?.fieldNr}, got \${tag.fieldNr}.\")"
.scoped(FqName.RpcClasses.ProtobufDecodingException)
)
})
Expand Down
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