gRPC Initial Implementation (#262)

Author: Mr3zee

build.gradle.kts

@@ -3,15 +3,16 @@
  */
 
 import org.jetbrains.kotlin.gradle.plugin.getKotlinPluginVersion
-import util.configureApiValidation
-import util.configureNpm
-import util.configureProjectReport
 import util.libs
+import util.configureProjectReport
+import util.configureNpm
+import util.configureApiValidation
 
 plugins {
     alias(libs.plugins.serialization) apply false
     alias(libs.plugins.kotlinx.rpc) apply false
     alias(libs.plugins.conventions.kover)
+    alias(libs.plugins.protobuf) apply false
     alias(libs.plugins.conventions.gradle.doctor)
     alias(libs.plugins.atomicfu)
     id("build-util")

compiler-plugin/compiler-plugin-backend/src/main/core/kotlinx/rpc/codegen/extension/RpcIrContext.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2023-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.rpc.codegen.extension
@@ -105,6 +105,14 @@ internal class RpcIrContext(
         getRpcIrClassSymbol("RpcServiceDescriptor", "descriptor")
     }
 
+    val grpcServiceDescriptor by lazy {
+        getIrClassSymbol("kotlinx.rpc.grpc.descriptor", "GrpcServiceDescriptor")
+    }
+
+    val grpcDelegate by lazy {
+        getIrClassSymbol("kotlinx.rpc.grpc.descriptor", "GrpcDelegate")
+    }
+
     val rpcType by lazy {
         getRpcIrClassSymbol("RpcType", "descriptor")
     }
@@ -262,6 +270,10 @@ internal class RpcIrContext(
             rpcServiceDescriptor.namedProperty("fqName")
         }
 
+        val grpcServiceDescriptorDelegate by lazy {
+            grpcServiceDescriptor.namedProperty("delegate")
+        }
+
         private fun IrClassSymbol.namedProperty(name: String): IrPropertySymbol {
             return owner.properties.single { it.name.asString() == name }.symbol
         }
@@ -276,7 +288,7 @@ internal class RpcIrContext(
         return getIrClassSymbol("kotlinx.rpc$suffix", name)
     }
 
-    private fun getIrClassSymbol(packageName: String, name: String): IrClassSymbol {
+    fun getIrClassSymbol(packageName: String, name: String): IrClassSymbol {
         return versionSpecificApi.referenceClass(pluginContext, packageName, name)
             ?: error("Unable to find symbol. Package: $packageName, name: $name")
     }

compiler-plugin/compiler-plugin-backend/src/main/core/kotlinx/rpc/codegen/extension/RpcIrServiceProcessor.kt

@@ -17,7 +17,9 @@ internal class RpcIrServiceProcessor(
     private val logger: MessageCollector,
 ) : IrElementTransformer<RpcIrContext> {
     override fun visitClass(declaration: IrClass, data: RpcIrContext): IrStatement {
-        if (declaration.hasAnnotation(RpcClassId.rpcAnnotation) && declaration.isInterface) {
+        if ((declaration.hasAnnotation(RpcClassId.rpcAnnotation)
+            || declaration.hasAnnotation(RpcClassId.grpcAnnotation)) && declaration.isInterface
+        ) {
             processService(declaration, data)
         }
 

compiler-plugin/compiler-plugin-backend/src/main/core/kotlinx/rpc/codegen/extension/RpcStubGenerator.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2023-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.rpc.codegen.extension
@@ -44,6 +44,10 @@ private object Descriptor {
     const val CREATE_INSTANCE = "createInstance"
 }
 
+private object GrpcDescriptor {
+    const val DELEGATE = "delegate"
+}
+
 @Suppress("detekt.LargeClass", "detekt.TooManyFunctions")
 internal class RpcStubGenerator(
     private val declaration: ServiceDeclaration,
@@ -123,7 +127,10 @@ internal class RpcStubGenerator(
 
         clientProperty()
 
-        coroutineContextProperty()
+        // not for gRPC
+        if (!declaration.isGrpc) {
+            coroutineContextProperty()
+        }
 
         declaration.fields.forEach {
             rpcFlowField(it)
@@ -550,7 +557,15 @@ internal class RpcStubGenerator(
             overriddenSymbols = listOf(method.function.symbol)
 
             body = irBuilder(symbol).irBlockBody {
-                +irReturn(
+                val call = if (declaration.isGrpc) {
+                    irRpcMethodClientCall(
+                        method = method,
+                        functionThisReceiver = functionThisReceiver,
+                        isMethodObject = isMethodObject,
+                        methodClass = methodClass,
+                        arguments = arguments,
+                    )
+                } else {
                     irCall(
                         callee = ctx.functions.scopedClientCall,
                         type = method.function.returnType,
@@ -600,7 +615,9 @@ internal class RpcStubGenerator(
 
                         putValueArgument(1, lambda)
                     }
-                )
+                }
+
+                +irReturn(call)
             }
         }
     }
@@ -868,7 +885,10 @@ internal class RpcStubGenerator(
             stubCompanionObjectThisReceiver = thisReceiver
                 ?: error("Stub companion object expected to have thisReceiver: ${name.asString()}")
 
-            superTypes = listOf(ctx.rpcServiceDescriptor.typeWith(declaration.serviceType))
+            superTypes = listOfNotNull(
+                ctx.rpcServiceDescriptor.typeWith(declaration.serviceType),
+                if (declaration.isGrpc) ctx.grpcServiceDescriptor.typeWith(declaration.serviceType) else null,
+            )
 
             generateCompanionObjectConstructor()
 
@@ -901,6 +921,10 @@ internal class RpcStubGenerator(
         generateCreateInstanceFunction()
 
         generateGetFieldsFunction()
+
+        if (declaration.isGrpc) {
+            generateGrpcDelegateProperty()
+        }
     }
 
     /**
@@ -1488,6 +1512,43 @@ internal class RpcStubGenerator(
         }
     }
 
+    /**
+     * override val delegate: GrpcDelegate = MyServiceDelegate
+     */
+    private fun IrClass.generateGrpcDelegateProperty() {
+        addProperty {
+            name = Name.identifier(GrpcDescriptor.DELEGATE)
+            visibility = DescriptorVisibilities.PUBLIC
+        }.apply {
+            overriddenSymbols = listOf(ctx.properties.grpcServiceDescriptorDelegate)
+
+            addBackingFieldUtil {
+                visibility = DescriptorVisibilities.PRIVATE
+                type = ctx.grpcDelegate.defaultType
+                vsApi { isFinalVS = true }
+            }.apply {
+                initializer = factory.createExpressionBody(
+                    IrGetObjectValueImpl(
+                        startOffset = UNDEFINED_OFFSET,
+                        endOffset = UNDEFINED_OFFSET,
+                        type = ctx.grpcDelegate.defaultType,
+                        symbol = ctx.getIrClassSymbol(
+                            declaration.service.packageFqName?.asString()
+                                ?: error("Expected package name fro service ${declaration.service.name}"),
+                            "${declaration.service.name.asString()}Delegate",
+                        ),
+                    )
+                )
+            }
+
+            addDefaultGetter(this@generateGrpcDelegateProperty, ctx.irBuiltIns) {
+                visibility = DescriptorVisibilities.PUBLIC
+                overriddenSymbols = listOf(ctx.properties.grpcServiceDescriptorDelegate.owner.getterOrFail.symbol)
+            }
+        }
+    }
+
+
     // Associated object annotation works on JS, WASM, and Native platforms.
     // See https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.reflect/find-associated-object.html
     private fun addAssociatedObjectAnnotationIfPossible() {

compiler-plugin/compiler-plugin-backend/src/main/core/kotlinx/rpc/codegen/extension/ServiceDeclaration.kt

@@ -1,15 +1,17 @@
 /*
- * Copyright 2023-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2023-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.rpc.codegen.extension
 
+import kotlinx.rpc.codegen.common.RpcClassId
 import org.jetbrains.kotlin.ir.declarations.IrClass
 import org.jetbrains.kotlin.ir.declarations.IrProperty
 import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
 import org.jetbrains.kotlin.ir.declarations.IrValueParameter
 import org.jetbrains.kotlin.ir.types.IrType
 import org.jetbrains.kotlin.ir.util.defaultType
+import org.jetbrains.kotlin.ir.util.hasAnnotation
 import org.jetbrains.kotlin.ir.util.kotlinFqName
 
 class ServiceDeclaration(
@@ -18,6 +20,7 @@ class ServiceDeclaration(
     val methods: List<Method>,
     val fields: List<FlowField>,
 ) {
+    val isGrpc = service.hasAnnotation(RpcClassId.grpcAnnotation)
     val fqName = service.kotlinFqName.asString()
 
     val serviceType = service.defaultType

compiler-plugin/compiler-plugin-common/src/main/core/kotlinx/rpc/codegen/common/Names.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2023-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.rpc.codegen.common
@@ -12,6 +12,7 @@ import org.jetbrains.kotlin.name.Name
 object RpcClassId {
     val remoteServiceInterface = ClassId(FqName("kotlinx.rpc"), Name.identifier("RemoteService"))
     val rpcAnnotation = ClassId(FqName("kotlinx.rpc.annotations"), Name.identifier("Rpc"))
+    val grpcAnnotation = ClassId(FqName("kotlinx.rpc.grpc.annotations"), Name.identifier("Grpc"))
     val checkedTypeAnnotation = ClassId(FqName("kotlinx.rpc.annotations"), Name.identifier("CheckedTypeAnnotation"))
 
     val serializableAnnotation = ClassId(FqName("kotlinx.serialization"), Name.identifier("Serializable"))

compiler-plugin/compiler-plugin-k2/src/main/core/kotlinx/rpc/codegen/FirGenerationKeys.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2023-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.rpc.codegen
@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlinx.serialization.compiler.fir.SerializationPluginKey
 
 internal class RpcGeneratedStubKey(
+    val isGrpc: Boolean,
     private val serviceName: Name,
     val functions: List<FirFunctionSymbol<*>>,
 ) : GeneratedDeclarationKey() {
@@ -25,6 +26,7 @@ internal val FirBasedSymbol<*>.generatedRpcServiceStubKey: RpcGeneratedStubKey?
     (origin as? FirDeclarationOrigin.Plugin)?.key as? RpcGeneratedStubKey
 
 internal class RpcGeneratedRpcMethodClassKey(
+    val isGrpc: Boolean,
     val rpcMethod: FirFunctionSymbol<*>,
 ) : GeneratedDeclarationKey() {
     val isObject = rpcMethod.valueParameterSymbols.isEmpty()

compiler-plugin/compiler-plugin-k2/src/main/core/kotlinx/rpc/codegen/FirRpcAdditionalCheckers.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023-2024 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ * Copyright 2023-2025 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
  */
 
 package kotlinx.rpc.codegen
@@ -25,6 +25,7 @@ class FirRpcAdditionalCheckers(
 ) : FirAdditionalCheckersExtension(session) {
     override fun FirDeclarationPredicateRegistrar.registerPredicates() {
         register(FirRpcPredicates.rpc)
+        register(FirRpcPredicates.grpc)
         register(FirRpcPredicates.checkedAnnotationMeta)
     }
 

compiler-plugin/compiler-plugin-k2/src/main/core/kotlinx/rpc/codegen/FirRpcPredicates.kt

@@ -16,6 +16,10 @@ object FirRpcPredicates {
         metaAnnotated(RpcClassId.rpcAnnotation.asSingleFqName(), includeItself = true)
     }
 
+    internal val grpc = DeclarationPredicate.create {
+        annotated(RpcClassId.grpcAnnotation.asSingleFqName()) // @Grpc
+    }
+
     internal val checkedAnnotationMeta = DeclarationPredicate.create {
         metaAnnotated(RpcClassId.checkedTypeAnnotation.asSingleFqName(), includeItself = false)
     }

compiler-plugin/compiler-plugin-k2/src/main/core/kotlinx/rpc/codegen/FirRpcServiceGenerator.kt

@@ -76,6 +76,7 @@ class FirRpcServiceGenerator(
 
     override fun FirDeclarationPredicateRegistrar.registerPredicates() {
         register(FirRpcPredicates.rpc)
+        register(FirRpcPredicates.grpc)
     }
 
     /**
@@ -113,7 +114,7 @@ class FirRpcServiceGenerator(
         val rpcMethodClassKey = classSymbol.generatedRpcMethodClassKey
 
         return when {
-            rpcMethodClassKey != null -> {
+            rpcMethodClassKey != null && !rpcMethodClassKey.isGrpc -> {
                 when {
                     !rpcMethodClassKey.isObject -> setOf(
                         SpecialNames.DEFAULT_NAME_FOR_COMPANION_OBJECT,
@@ -131,7 +132,10 @@ class FirRpcServiceGenerator(
                         SpecialNames.DEFAULT_NAME_FOR_COMPANION_OBJECT
             }
 
-            classSymbol.isInterface && session.predicateBasedProvider.matches(FirRpcPredicates.rpc, classSymbol) -> {
+            classSymbol.isInterface && (
+                    session.predicateBasedProvider.matches(FirRpcPredicates.rpc, classSymbol) ||
+                            session.predicateBasedProvider.matches(FirRpcPredicates.grpc, classSymbol)
+                    ) -> {
                 setOf(RpcNames.SERVICE_STUB_NAME)
             }
 
@@ -160,7 +164,7 @@ class FirRpcServiceGenerator(
                 generateRpcMethodClass(owner, name, rpcServiceStubKey)
             }
 
-            owner.generatedRpcMethodClassKey != null -> {
+            owner.generatedRpcMethodClassKey != null && owner.generatedRpcMethodClassKey?.isGrpc == false -> {
                 generateNestedClassLikeDeclarationWithSerialization(owner, name)
             }
 
@@ -192,7 +196,7 @@ class FirRpcServiceGenerator(
         val methodName = name.rpcMethodName
         val rpcMethod = rpcServiceStubKey.functions.singleOrNull { it.name == methodName }
             ?: return null
-        val rpcMethodClassKey = RpcGeneratedRpcMethodClassKey(rpcMethod)
+        val rpcMethodClassKey = RpcGeneratedRpcMethodClassKey(rpcServiceStubKey.isGrpc, rpcMethod)
         val classKind = if (rpcMethodClassKey.isObject) ClassKind.OBJECT else ClassKind.CLASS
 
         val rpcMethodClass = createNestedClass(
@@ -205,13 +209,15 @@ class FirRpcServiceGenerator(
             modality = Modality.FINAL
         }
 
-        rpcMethodClass.addAnnotation(RpcClassId.serializableAnnotation, session)
+        if (!session.predicateBasedProvider.matches(FirRpcPredicates.grpc, owner)) {
+            rpcMethodClass.addAnnotation(RpcClassId.serializableAnnotation, session)
+        }
 
         /**
          * Required to pass isSerializableObjectAndNeedsFactory check
          * from [SerializationFirSupertypesExtension].
          */
-        if (!isJvmOrMetadata && rpcMethodClassKey.isObject) {
+        if (!isJvmOrMetadata && rpcMethodClassKey.isObject && !rpcMethodClassKey.isGrpc) {
             rpcMethodClass.replaceSuperTypeRefs(createSerializationFactorySupertype())
         }
 
@@ -266,7 +272,13 @@ class FirRpcServiceGenerator(
             .filterIsInstance<FirFunction>()
             .map { it.symbol }
 
-        return createNestedClass(owner, RpcNames.SERVICE_STUB_NAME, RpcGeneratedStubKey(owner.name, functions)) {
+        val key = RpcGeneratedStubKey(
+            isGrpc = session.predicateBasedProvider.matches(FirRpcPredicates.grpc, owner),
+            serviceName = owner.name,
+            functions = functions,
+        )
+
+        return createNestedClass(owner, RpcNames.SERVICE_STUB_NAME, key) {
             visibility = Visibilities.Public
             modality = Modality.FINAL
         }.symbol
@@ -300,7 +312,7 @@ class FirRpcServiceGenerator(
         context: MemberGenerationContext,
         rpcMethodClassKey: RpcGeneratedRpcMethodClassKey,
     ): Set<Name> {
-        return if (rpcMethodClassKey.isObject) {
+        return if (rpcMethodClassKey.isObject && !rpcMethodClassKey.isGrpc) {
             // add .serializer() method for a serializable object
             serializationExtension.getCallableNamesForClass(classSymbol, context)
         } else {