Test jvm constraints plugin now configures jmh plugin

buildSrc/build.gradle.kts

@@ -109,6 +109,8 @@ dependencies {
   implementation("com.fasterxml.jackson.core:jackson-core")
 
   compileOnly(libs.develocity)
+
+  testImplementation("me.champeau.jmh:jmh-gradle-plugin:0.7.3")
 }
 
 tasks.compileKotlin {

buildSrc/src/main/kotlin/datadog/gradle/plugin/testJvmConstraints/TestJvmConstraintsPlugin.kt

@@ -6,6 +6,7 @@ import org.gradle.api.JavaVersion
 import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.gradle.api.plugins.JavaPlugin
+import org.gradle.api.provider.Property
 import org.gradle.api.provider.Provider
 import org.gradle.api.tasks.testing.Test
 import org.gradle.kotlin.dsl.*
@@ -42,6 +43,16 @@ class TestJvmConstraintsPlugin : Plugin<Project> {
       configureTestJvm(testJvmSpec, taskExtension)
     }
 
+    // JMH plugin is not applied on every project
+    project.pluginManager.withPlugin("me.champeau.jmh") {
+      val jmh = project.extensions.getByName("jmh")
+
+      // Avoid linking against JMH types, which are unavailable to the parent buildSrc classloader.
+      @Suppress("UNCHECKED_CAST")
+      val jvm = jmh.javaClass.getMethod("getJvm").invoke(jmh) as Property<String>
+      jvm.set(testJvmSpec.javaTestLauncher.map { it.executablePath.asFile.absolutePath })
+    }
+
     // Jacoco plugin is not applied on every project
     project.pluginManager.withPlugin("org.gradle.jacoco") {
       project.tasks.withType<Test>().configureEach {

buildSrc/src/test/kotlin/datadog/gradle/plugin/testJvmConstraints/TestJvmConstraintsPluginTest.kt

@@ -1,7 +1,9 @@
 package datadog.gradle.plugin.testJvmConstraints
 
 import datadog.gradle.plugin.testJvmConstraints.TestJvmConstraintsExtension.Companion.TEST_JVM_CONSTRAINTS
+import me.champeau.jmh.JmhParameters
 import org.assertj.core.api.Assertions.assertThat
+import org.gradle.api.JavaVersion
 import org.gradle.api.tasks.testing.Test as GradleTest
 import org.gradle.testfixtures.ProjectBuilder
 import org.gradle.testing.jacoco.plugins.JacocoTaskExtension
@@ -21,6 +23,31 @@ class TestJvmConstraintsPluginTest {
     assertThat(testTask.extensions.findByName(TEST_JVM_CONSTRAINTS)).isInstanceOf(TestJvmConstraintsExtension::class.java)
   }
 
+  @Test
+  fun `plugin configures jmh to use the test jvm`() {
+    val propertyName = "org.gradle.project.${TestJvmSpec.TEST_JVM}"
+    val previousValue = System.setProperty(propertyName, JavaVersion.current().majorVersion)
+
+    try {
+      val project = ProjectBuilder.builder().build()
+
+      project.pluginManager.apply("dd-trace-java.test-jvm-constraints")
+      assertThat(project.extensions.findByName("jmh")).isNull()
+
+      project.pluginManager.apply("me.champeau.jmh")
+
+      val jmh = project.extensions.getByType(JmhParameters::class.java)
+      val expectedExecutable = TestJvmSpec(project).javaTestLauncher.get().executablePath.asFile.absolutePath
+      assertThat(jmh.jvm.get()).isEqualTo(expectedExecutable)
+    } finally {
+      if (previousValue == null) {
+        System.clearProperty(propertyName)
+      } else {
+        System.setProperty(propertyName, previousValue)
+      }
+    }
+  }
+
   @Test
   fun `jacoco is disabled for additional test jvm when coverage is not checked`() {
     val testTask = testTaskWithJacoco()

dd-trace-core/build.gradle

@@ -1,5 +1,3 @@
-import datadog.gradle.plugin.testJvmConstraints.TestJvmSpec
-
 plugins {
   id 'me.champeau.jmh'
   id 'dd-trace-java.version-file'
@@ -135,8 +133,4 @@ jmh {
   if (project.hasProperty('jmh.profilers')) {
     profilers = project.property('jmh.profilers').tokenize(',')
   }
-  if (project.hasProperty('testJvm')) {
-    def testJvmSpec = new TestJvmSpec(project)
-    jvm = testJvmSpec.javaTestLauncher.map { it.executablePath.asFile.absolutePath }
-  }
 }

internal-api/build.gradle.kts

@@ -1,4 +1,3 @@
-import datadog.gradle.plugin.testJvmConstraints.TestJvmSpec
 import de.thetaphi.forbiddenapis.gradle.CheckForbiddenApis
 import groovy.lang.Closure
 
@@ -291,9 +290,4 @@ jmh {
   if (project.hasProperty("jmh.includes")) {
     includes.add(project.property("jmh.includes") as String)
   }
-
-  if (project.hasProperty("testJvm")) {
-    val testJvmSpec = TestJvmSpec(project)
-    jvm.set(testJvmSpec.javaTestLauncher.map { it.executablePath.asFile.absolutePath })
-  }
 }