Use Kotlin 2.3's generatedKotlin API

Author: oldergod

wire-gradle-plugin/src/main/kotlin/com/squareup/wire/gradle/kotlin/SourceRoots.kt

@@ -26,11 +26,14 @@ import com.squareup.wire.schema.ProtoTarget
 import com.squareup.wire.schema.Target
 import java.io.File
 import org.gradle.api.Project
+import org.gradle.api.file.Directory
 import org.gradle.api.file.SourceDirectorySet
+import org.gradle.api.provider.Provider
 import org.gradle.api.tasks.SourceSetContainer
 import org.gradle.api.tasks.TaskProvider
 import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
 import org.jetbrains.kotlin.gradle.dsl.KotlinProjectExtension
+import org.jetbrains.kotlin.gradle.plugin.KotlinSourceSet
 
 internal fun forEachWireSource(
   project: Project,
@@ -63,12 +66,12 @@ internal fun forEachWireSource(
     hasKotlin -> {
       val kotlinSourceSets = project.extensions.findByType(KotlinProjectExtension::class.java)?.sourceSets
       val javaSourceSets = project.extensions.findByType(SourceSetContainer::class.java)
-      val kotlinSourceDirectorySet = kotlinSourceSets?.findByName("main")?.kotlin
+      val kotlinSourceSet = kotlinSourceSets?.findByName("main")
       val javaSourceDirectorySet = javaSourceSets?.findByName("main")?.java
       val source = JvmOrKmpSource(
         name = "main",
         sourceSets = listOf("main"),
-        kotlinSourceDirectorySet = kotlinSourceDirectorySet,
+        kotlinSourceSet = kotlinSourceSet,
         javaSourceDirectorySet = javaSourceDirectorySet,
       )
       sourceHandler(source)
@@ -79,7 +82,7 @@ internal fun forEachWireSource(
       val source = JvmOrKmpSource(
         name = "main",
         sourceSets = listOf("main"),
-        kotlinSourceDirectorySet = null,
+        kotlinSourceSet = null,
         javaSourceDirectorySet = javaSourceDirectorySet,
       )
       sourceHandler(source)
@@ -115,7 +118,7 @@ private fun KotlinMultiplatformExtension.sourceRoots(): List<WireSource> {
   return listOf(
     JvmOrKmpSource(
       name = "commonMain",
-      kotlinSourceDirectorySet = sourceSets.getByName("commonMain").kotlin,
+      kotlinSourceSet = sourceSets.getByName("commonMain"),
       javaSourceDirectorySet = null,
       sourceSets = listOf("commonMain"),
     ),
@@ -125,7 +128,7 @@ private fun KotlinMultiplatformExtension.sourceRoots(): List<WireSource> {
 private class JvmOrKmpSource(
   name: String,
   sourceSets: List<String>,
-  private val kotlinSourceDirectorySet: SourceDirectorySet?,
+  private val kotlinSourceSet: KotlinSourceSet?,
   private val javaSourceDirectorySet: SourceDirectorySet?,
 ) : WireSource(name, sourceSets) {
   override fun outputDir(project: Project): File {
@@ -144,12 +147,12 @@ private class JvmOrKmpSource(
           javaSourceDirectorySet?.srcDir(outputDirectory)
         }
         is KotlinTarget -> {
-          kotlinSourceDirectorySet?.srcDir(outputDirectory)
+          registerKotlinGeneratedSources(kotlinSourceSet, outputDirectory)
         }
         is CustomTarget -> {
           // Custom targets are wildcards, so we add all output directories.
           javaSourceDirectorySet?.srcDir(outputDirectory)
-          kotlinSourceDirectorySet?.srcDir(outputDirectory)
+          registerKotlinGeneratedSources(kotlinSourceSet, outputDirectory)
         }
         is ProtoTarget -> {
           // Do nothing
@@ -203,3 +206,28 @@ private class AndroidSource(
     }
   }
 }
+
+/**
+ * Registers [outputDirectory] as a generated Kotlin source directory on [kotlinSourceSet].
+ *
+ * On Kotlin 2.3+, uses the [KotlinSourceSet.generatedKotlin] API so that IDEs can distinguish
+ * generated sources from hand-written ones. Falls back to [KotlinSourceSet.kotlin] on older
+ * versions of the Kotlin Gradle Plugin where the API is not available.
+ */
+private fun registerKotlinGeneratedSources(
+  kotlinSourceSet: KotlinSourceSet?,
+  outputDirectory: Provider<Directory>,
+) {
+  if (kotlinSourceSet == null) return
+  // generatedKotlin was introduced experimentally in Kotlin 2.3. Detect it reflectively so that
+  // Wire remains compatible with earlier Kotlin Gradle Plugin versions.
+  val generatedKotlinMethod = runCatching {
+    kotlinSourceSet.javaClass.getMethod("getGeneratedKotlin")
+  }.getOrNull()
+  if (generatedKotlinMethod != null) {
+    val generatedKotlin = generatedKotlinMethod.invoke(kotlinSourceSet) as SourceDirectorySet
+    generatedKotlin.srcDir(outputDirectory)
+  } else {
+    kotlinSourceSet.kotlin.srcDir(outputDirectory)
+  }
+}

wire-gradle-plugin/src/test/kotlin/com/squareup/wire/gradle/WirePluginTest.kt

@@ -680,6 +680,38 @@ class WirePluginTest {
     assertThat(File(outputRoot, "com/squareup/geology/Period.kt")).exists()
   }
 
+  /**
+   * Verifies that generated Kotlin sources are registered on the Kotlin source set so that
+   * `compileKotlin` picks them up. This exercises the fallback path in
+   * [com.squareup.wire.gradle.kotlin.registerKotlinGeneratedSources] for KGP < 2.3, where
+   * `KotlinSourceSet.generatedKotlin` is not available and we fall back to `kotlin.srcDir()`.
+   */
+  @Test
+  fun kotlinProjectKotlinProtosCompiles() {
+    val fixtureRoot = File("src/test/projects/kotlin-project-kotlin-protos")
+
+    val result = fixtureGradleRunner(fixtureRoot, "clean", "build").build()
+
+    assertThat(result.task(":generateMainProtos")).isNotNull()
+    assertThat(result.task(":compileKotlin")).isNotNull()
+  }
+
+  /**
+   * Verifies that generated Kotlin sources are registered via `KotlinSourceSet.generatedKotlin`
+   * (the API introduced experimentally in Kotlin 2.3) and that `compileKotlin` picks them up.
+   * The fixture uses a hardcoded KGP 2.3.x dependency so that the new code path in
+   * [com.squareup.wire.gradle.kotlin.registerKotlinGeneratedSources] is exercised.
+   */
+  @Test
+  fun kotlinProjectKotlinProtosWithGeneratedKotlinApi() {
+    val fixtureRoot = File("src/test/projects/kotlin-project-kotlin-protos-kgp23")
+
+    val result = fixtureGradleRunner(fixtureRoot, "clean", "build").build()
+
+    assertThat(result.task(":generateMainProtos")).isNotNull()
+    assertThat(result.task(":compileKotlin")).isNotNull()
+  }
+
   @Test
   fun protoLibrary() {
     val fixtureRoot = File("src/test/projects/proto-library")

wire-gradle-plugin/src/test/projects/kotlin-project-kotlin-protos-kgp23/build.gradle

@@ -0,0 +1,49 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+buildscript {
+  dependencies {
+    classpath "com.squareup.wire:wire-gradle-plugin:$wireVersion"
+    // Hardcoded to test the KotlinSourceSet.generatedKotlin API introduced in Kotlin 2.3.
+    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:2.3.20"
+  }
+
+  repositories {
+    maven {
+      url new File(rootDir, "../../../../../build/localMaven").toURI().toString()
+    }
+    mavenCentral()
+    google()
+  }
+}
+
+apply plugin: 'application'
+apply plugin: 'org.jetbrains.kotlin.jvm'
+apply plugin: 'com.squareup.wire'
+
+application.mainClass = "com.squareup.dinosaurs.Sample"
+
+repositories {
+  maven {
+    url new File(rootDir, "../../../../../build/localMaven").toURI().toString()
+  }
+  mavenCentral()
+}
+
+dependencies {
+  implementation "com.squareup.wire:wire-runtime:$wireVersion"
+}
+
+wire {
+  kotlin {}
+}
+
+tasks.withType(JavaCompile).configureEach {
+  sourceCompatibility = JavaVersion.VERSION_11.toString()
+  targetCompatibility = JavaVersion.VERSION_11.toString()
+}
+
+tasks.withType(KotlinCompile).configureEach {
+  kotlinOptions {
+    jvmTarget = "11"
+  }
+}

wire-gradle-plugin/src/test/projects/kotlin-project-kotlin-protos-kgp23/settings.gradle

@@ -0,0 +1 @@
+include ':'

wire-gradle-plugin/src/test/projects/kotlin-project-kotlin-protos-kgp23/src/main/java/com/squareup/dinosaurs/Sample.kt

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2023 Square, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.squareup.dinosaurs
+
+import com.squareup.geology.Period
+import java.io.IOException
+import okio.ByteString.Companion.toByteString
+
+class Sample {
+  @Throws(IOException::class)
+  fun run() {
+    // Create an immutable value object with the Builder API.
+    val stegosaurus = Dinosaur(
+      name = "Stegosaurus",
+      period = Period.JURASSIC,
+      length_meters = 9.0,
+      mass_kilograms = 5_000.0,
+      picture_urls = listOf("http://goo.gl/LD5KY5", "http://goo.gl/VYRM67"),
+    )
+    // Encode that value to bytes, and print that as base64.
+    val stegosaurusEncoded = Dinosaur.ADAPTER.encode(stegosaurus)
+    println(stegosaurusEncoded.toByteString().base64())
+  }
+
+  companion object {
+    @Throws(IOException::class)
+    @JvmStatic
+    fun main(args: Array<String>) {
+      Sample().run()
+    }
+  }
+}

wire-gradle-plugin/src/test/projects/kotlin-project-kotlin-protos-kgp23/src/main/proto/squareup/dinosaurs/dinosaur.proto

@@ -0,0 +1,19 @@
+syntax = "proto2";
+
+package squareup.dinosaurs;
+
+option java_package = "com.squareup.dinosaurs";
+
+import "squareup/geology/period.proto";
+
+message Dinosaur {
+  /** Common name of this dinosaur, like "Stegosaurus". */
+  optional string name = 1;
+
+  /** URLs with images of this dinosaur. */
+  repeated string picture_urls = 2;
+
+  optional double length_meters = 3;
+  optional double mass_kilograms = 4;
+  optional squareup.geology.Period period = 5;
+}

wire-gradle-plugin/src/test/projects/kotlin-project-kotlin-protos-kgp23/src/main/proto/squareup/geology/period.proto

@@ -0,0 +1,16 @@
+syntax = "proto2";
+
+package squareup.geology;
+
+option java_package = "com.squareup.geology";
+
+enum Period {
+  /** 145.5 million years ago — 66.0 million years ago. */
+  CRETACEOUS = 1;
+
+  /** 201.3 million years ago — 145.0 million years ago. */
+  JURASSIC = 2;
+
+  /** 252.17 million years ago — 201.3 million years ago. */
+  TRIASSIC = 3;
+}