Switching to Kotlin Multiplatform for JVM use (#1654)

* Transition to Kotlin Multiplatform for JVM use

* Use jvmTest task instead of test task

* Apply KMP plugin only to the kotlinpoet module

* Fix setup check task

* Fix targetExclude folder as the source set name change

* Move Java code to jvmMain directory

* Apply dokka workaround

* Use js(IR) as phantom target

* Update kotlinpoet/build.gradle.kts

* Update kotlinpoet/build.gradle.kts

* Update kotlinpoet/build.gradle.kts

* Update gradle/libs.versions.toml

* Update kotlinpoet/build.gradle.kts

---------

Co-authored-by: Jake Wharton <[email protected]>

build.gradle.kts

@@ -17,10 +17,12 @@ import com.diffplug.gradle.spotless.SpotlessExtension
 import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 import org.jetbrains.dokka.gradle.DokkaTask
 import org.jetbrains.kotlin.gradle.dsl.JvmTarget
+import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
 import org.jetbrains.kotlin.gradle.dsl.KotlinProjectExtension
 import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
 
 plugins {
+  alias(libs.plugins.kotlin.multiplatform) apply false
   alias(libs.plugins.kotlin.jvm) apply false
   alias(libs.plugins.ksp) apply false
   alias(libs.plugins.dokka) apply false
@@ -53,12 +55,18 @@ subprojects {
     options.release.set(8)
   }
 
-  apply(plugin = "org.jetbrains.kotlin.jvm")
   if ("test" !in name && buildFile.exists()) {
     apply(plugin = "org.jetbrains.dokka")
     apply(plugin = "com.vanniktech.maven.publish")
-    configure<KotlinProjectExtension> {
-      explicitApi()
+    pluginManager.withPlugin("org.jetbrains.kotlin.multiplatform") {
+      configure<KotlinMultiplatformExtension> {
+        explicitApi()
+      }
+    }
+    pluginManager.withPlugin("org.jetbrains.kotlin.jvm") {
+      configure<KotlinProjectExtension> {
+        explicitApi()
+      }
     }
     afterEvaluate {
       tasks.named<DokkaTask>("dokkaHtml") {
@@ -70,7 +78,6 @@ subprojects {
       }
     }
   }
-
   apply(plugin = "com.diffplug.spotless")
   configure<SpotlessExtension> {
     kotlin {
@@ -98,40 +105,52 @@ subprojects {
         | * See the License for the specific language governing permissions and
         | * limitations under the License.
         | */
-        """.trimMargin()
+        """.trimMargin(),
       )
     }
   }
 
   // Only enable the extra toolchain tests on CI. Otherwise local development is broken on Apple Silicon macs
   // because there are no matching toolchains for several older JDK versions.
   if ("CI" in System.getenv()) {
-    // Copied from https://github.com/square/retrofit/blob/master/retrofit/build.gradle#L28.
-    // Create a test task for each supported JDK. We check every "LTS" + current version.
-    val versionsToTest = listOf(8, 11, 17, 19)
-    for (majorVersion in versionsToTest) {
-      val jdkTest = tasks.register<Test>("testJdk$majorVersion") {
-        val javaToolchains = project.extensions.getByType(JavaToolchainService::class)
-        javaLauncher.set(javaToolchains.launcherFor {
-          languageVersion.set(JavaLanguageVersion.of(majorVersion))
-          vendor.set(JvmVendorSpec.AZUL)
-        })
+    fun Project.setupCheckTask(testTaskName: String) {
+      // Copied from https://github.com/square/retrofit/blob/master/retrofit/build.gradle#L28.
+      // Create a test task for each supported JDK. We check every "LTS" + current version.
+      val versionsToTest = listOf(8, 11, 17, 19)
+      for (majorVersion in versionsToTest) {
+        val jdkTest = tasks.register<Test>("testJdk$majorVersion") {
+          val javaToolchains = project.extensions.getByType(JavaToolchainService::class)
+          javaLauncher.set(
+            javaToolchains.launcherFor {
+              languageVersion.set(JavaLanguageVersion.of(majorVersion))
+              vendor.set(JvmVendorSpec.AZUL)
+            },
+          )
+
+          description = "Runs the test suite on JDK $majorVersion"
+          group = LifecycleBasePlugin.VERIFICATION_GROUP
 
-        description = "Runs the test suite on JDK $majorVersion"
-        group = LifecycleBasePlugin.VERIFICATION_GROUP
+          // Copy inputs from normal Test task.
+          val testTask =
+            tasks.getByName<Test>(testTaskName)
 
-        // Copy inputs from normal Test task.
-        val testTask = tasks.getByName<Test>("test")
-        classpath = testTask.classpath
-        testClassesDirs = testTask.testClassesDirs
+          classpath = testTask.classpath
+          testClassesDirs = testTask.testClassesDirs
 
-        testLogging {
-          exceptionFormat = TestExceptionFormat.FULL
+          testLogging {
+            exceptionFormat = TestExceptionFormat.FULL
+          }
+        }
+        tasks.named("check").configure {
+          dependsOn(jdkTest)
         }
       }
-      tasks.named("check").configure {
-        dependsOn(jdkTest)
-      }
+    }
+    pluginManager.withPlugin("org.jetbrains.kotlin.multiplatform") {
+      setupCheckTask("jvmTest")
+    }
+    pluginManager.withPlugin("org.jetbrains.kotlin.jvm") {
+      setupCheckTask("test")
     }
   }
 }
@@ -140,6 +159,6 @@ apiValidation {
   nonPublicMarkers += "com.squareup.kotlinpoet.ExperimentalKotlinPoetApi"
   ignoredProjects += listOf(
     "interop", // Empty middle package
-    "test-processor" // Test only
+    "test-processor", // Test only
   )
 }

gradle/libs.versions.toml

@@ -19,6 +19,7 @@ ksp = "1.9.10-1.0.13"
 ktlint = "0.48.2"
 
 [plugins]
+kotlin-multiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }
 kotlin-jvm = { id = "org.jetbrains.kotlin.jvm", version.ref = "kotlin" }
 dokka = { id = "org.jetbrains.dokka", version = "1.9.10" }
 ksp = { id = "com.google.devtools.ksp", version.ref = "ksp" }

interop/javapoet/build.gradle.kts

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+plugins {
+  kotlin("jvm")
+}
 
 tasks.jar {
   manifest {

interop/kotlinx-metadata/build.gradle.kts

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+plugins {
+  kotlin("jvm")
+}
 
 tasks.jar {
   manifest {

interop/ksp/build.gradle.kts

@@ -13,6 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+plugins {
+  kotlin("jvm")
+}
 
 tasks.jar {
   manifest {

interop/ksp/test-processor/build.gradle.kts

@@ -15,6 +15,7 @@
  */
 plugins {
   id("com.google.devtools.ksp")
+  kotlin("jvm")
 }
 
 tasks.compileTestKotlin {

kotlinpoet/build.gradle.kts

@@ -13,40 +13,59 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-tasks.jar {
-  manifest {
-    attributes("Automatic-Module-Name" to "com.squareup.kotlinpoet")
-  }
-}
-
-tasks.compileTestKotlin {
-  compilerOptions {
-    freeCompilerArgs.add("-opt-in=com.squareup.kotlinpoet.DelicateKotlinPoetApi")
-  }
+plugins {
+  kotlin("multiplatform")
 }
 
 spotless {
   kotlin {
     targetExclude(
       // Non-Square licensed files
-      "src/main/java/com/squareup/kotlinpoet/ClassName.kt",
-      "src/test/java/com/squareup/kotlinpoet/AbstractTypesTest.kt",
-      "src/test/java/com/squareup/kotlinpoet/ClassNameTest.kt",
-      "src/test/java/com/squareup/kotlinpoet/TypesEclipseTest.kt",
-      "src/test/java/com/squareup/kotlinpoet/TypesTest.kt",
+      "src/commonMain/kotlin/com/squareup/kotlinpoet/ClassName.kt",
+      "src/commonTest/kotlin/com/squareup/kotlinpoet/AbstractTypesTest.kt",
+      "src/commonTest/kotlin/com/squareup/kotlinpoet/ClassNameTest.kt",
+      "src/commonTest/kotlin/com/squareup/kotlinpoet/TypesEclipseTest.kt",
+      "src/commonTest/kotlin/com/squareup/kotlinpoet/TypesTest.kt",
     )
   }
 }
 
-dependencies {
-  implementation(libs.kotlin.reflect)
-  testImplementation(libs.kotlin.junit)
-  testImplementation(libs.truth)
-  testImplementation(libs.guava)
-  testImplementation(libs.compileTesting)
-  testImplementation(libs.jimfs)
-  testImplementation(libs.ecj)
-  testImplementation(libs.kotlinCompileTesting)
-  testImplementation(libs.kotlin.annotationProcessingEmbeddable)
-  testImplementation(libs.kotlin.compilerEmbeddable)
+kotlin {
+  jvm {
+    withJava()
+  }
+
+  sourceSets {
+    val commonMain by getting {
+      dependencies {
+        implementation(libs.kotlin.reflect)
+      }
+    }
+    val commonTest by getting {
+      dependencies {
+        implementation(libs.kotlin.junit)
+        implementation(libs.truth)
+        implementation(libs.guava)
+        implementation(libs.compileTesting)
+        implementation(libs.jimfs)
+        implementation(libs.ecj)
+        implementation(libs.kotlinCompileTesting)
+        implementation(libs.kotlin.annotationProcessingEmbeddable)
+        implementation(libs.kotlin.compilerEmbeddable)
+      }
+    }
+  }
+}
+
+tasks.withType(org.gradle.jvm.tasks.Jar::class.java) {
+  manifest {
+    attributes("Automatic-Module-Name" to "com.squareup.kotlinpoet")
+  }
 }
+
+tasks.named<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>("compileTestKotlinJvm") {
+  compilerOptions {
+    freeCompilerArgs.add("-opt-in=com.squareup.kotlinpoet.DelicateKotlinPoetApi")
+  }
+}
+

kotlinpoet/src/test/java/com/squareup/kotlinpoet/AnnotationSpecTest.kt → kotlinpoet/src/commonTest/kotlin/com/squareup/kotlinpoet/AnnotationSpecTest.kt

@@ -345,32 +345,6 @@ class AnnotationSpecTest {
     )
   }
 
-  @Test fun getOnValueArrayTypeMirrorShouldNameValueArg() {
-    val myClazz = compilation.elements
-      .getTypeElement(JavaClassWithArrayValueAnnotation::class.java.canonicalName)
-    val classBuilder = TypeSpec.classBuilder("Result")
-
-    myClazz.annotationMirrors.map { AnnotationSpec.get(it) }
-      .forEach {
-        classBuilder.addAnnotation(it)
-      }
-
-    assertThat(toString(classBuilder.build())).isEqualTo(
-      """
-            |package com.squareup.tacos
-            |
-            |import com.squareup.kotlinpoet.JavaClassWithArrayValueAnnotation
-            |import java.lang.Boolean
-            |import java.lang.Object
-            |
-            |@JavaClassWithArrayValueAnnotation.AnnotationWithArrayValue(value = arrayOf(Object::class,
-            |        Boolean::class))
-            |public class Result
-            |
-      """.trimMargin(),
-    )
-  }
-
   @Test fun getOnVarargMirrorShouldNameValueArg() {
     val myClazz = compilation.elements
       .getTypeElement(KotlinClassWithVarargAnnotation::class.java.canonicalName)
@@ -399,28 +373,6 @@ class AnnotationSpecTest {
     )
   }
 
-  @Test fun getOnValueArrayTypeAnnotationShouldNameValueArg() {
-    val annotation = JavaClassWithArrayValueAnnotation::class.java.getAnnotation(
-      JavaClassWithArrayValueAnnotation.AnnotationWithArrayValue::class.java,
-    )
-    val classBuilder = TypeSpec.classBuilder("Result")
-      .addAnnotation(AnnotationSpec.get(annotation))
-
-    assertThat(toString(classBuilder.build()).trim()).isEqualTo(
-      """
-        |package com.squareup.tacos
-        |
-        |import com.squareup.kotlinpoet.JavaClassWithArrayValueAnnotation
-        |import java.lang.Boolean
-        |import java.lang.Object
-        |
-        |@JavaClassWithArrayValueAnnotation.AnnotationWithArrayValue(value = arrayOf(Object::class,
-        |        Boolean::class))
-        |public class Result
-      """.trimMargin(),
-    )
-  }
-
   @Test fun getOnVarargAnnotationShouldNameValueArg() {
     val annotation = KotlinClassWithVarargAnnotation::class.java
       .getAnnotation(AnnotationWithArrayValue::class.java)

kotlinpoet/src/jvmTest/java/com/squareup/kotlinpoet/JavaAnnotationSpecTest.kt

@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2015 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.kotlinpoet
+
+import com.google.common.truth.Truth.assertThat
+import com.google.testing.compile.CompilationRule
+import kotlin.test.Test
+import org.junit.Rule
+
+class JavaAnnotationSpecTest {
+
+  @Rule @JvmField
+  val compilation = CompilationRule()
+
+  @Test fun getOnValueArrayTypeMirrorShouldNameValueArg() {
+    val myClazz = compilation.elements
+      .getTypeElement(JavaClassWithArrayValueAnnotation::class.java.canonicalName)
+    val classBuilder = TypeSpec.classBuilder("Result")
+
+    myClazz.annotationMirrors.map { AnnotationSpec.get(it) }
+      .forEach {
+        classBuilder.addAnnotation(it)
+      }
+
+    assertThat(toString(classBuilder.build())).isEqualTo(
+      """
+            |package com.squareup.tacos
+            |
+            |import com.squareup.kotlinpoet.JavaClassWithArrayValueAnnotation
+            |import java.lang.Boolean
+            |import java.lang.Object
+            |
+            |@JavaClassWithArrayValueAnnotation.AnnotationWithArrayValue(value = arrayOf(Object::class,
+            |        Boolean::class))
+            |public class Result
+            |
+      """.trimMargin(),
+    )
+  }
+
+  @Test fun getOnValueArrayTypeAnnotationShouldNameValueArg() {
+    val annotation = JavaClassWithArrayValueAnnotation::class.java.getAnnotation(
+      JavaClassWithArrayValueAnnotation.AnnotationWithArrayValue::class.java,
+    )
+    val classBuilder = TypeSpec.classBuilder("Result")
+      .addAnnotation(AnnotationSpec.get(annotation))
+
+    assertThat(toString(classBuilder.build()).trim()).isEqualTo(
+      """
+        |package com.squareup.tacos
+        |
+        |import com.squareup.kotlinpoet.JavaClassWithArrayValueAnnotation
+        |import java.lang.Boolean
+        |import java.lang.Object
+        |
+        |@JavaClassWithArrayValueAnnotation.AnnotationWithArrayValue(value = arrayOf(Object::class,
+        |        Boolean::class))
+        |public class Result
+      """.trimMargin(),
+    )
+  }
+
+  private fun toString(typeSpec: TypeSpec) =
+    FileSpec.get("com.squareup.tacos", typeSpec).toString()
+}