From 541652c2ed9b79b6700b526a48257d74b842c1d2 Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Wed, 20 Aug 2025 20:03:53 +0200
Subject: [PATCH 01/23] Intial Groovy setup

---
 .../api/daemon/internal/GroovyModuleApi.scala |   3 +
 .../daemon/internal/bsp/BspModuleApi.scala    |   1 +
 .../groovylib/worker/api/GroovyWorker.scala   |  12 +
 libs/groovylib/package.mill                   |  50 ++++
 .../mill/groovylib/GroovyMavenModule.scala    |  20 ++
 .../src/mill/groovylib/GroovyModule.scala     | 269 ++++++++++++++++++
 .../mill/groovylib/GroovyWorkerManager.scala  |  40 +++
 .../groovylib/TestGroovyMavenModule.scala     |  25 ++
 .../src/mill/groovylib/exports.scala          |  13 +
 .../src/mill/groovylib/groovylib.scala        |   7 +
 .../src/mill/groovylib/publish/exports.scala  |  35 +++
 .../main/script/src/HelloScript.groovy        |   8 +
 .../main/spock/src/SpockTest.groovy           |  21 ++
 .../hello-groovy/main/src/Hello.groovy        |  16 ++
 .../main/staticcompile/src/HelloStatic.groovy |  26 ++
 .../main/test/src/HelloTest.groovy            |  12 +
 .../src/mill/groovylib/HelloGroovyTests.scala | 185 ++++++++++++
 .../worker/impl/GroovyWorkerImpl.scala        |  43 +++
 .../javalib/src/mill/javalib/TestModule.scala |  39 ++-
 .../src/mill/kotlinlib/publish/exports.scala  |   2 +-
 .../src/mill/kotlinlib/HelloKotlinTests.scala |   1 +
 libs/package.mill                             |   1 +
 mill-build/src/millbuild/Deps.scala           |   2 +
 23 files changed, 828 insertions(+), 3 deletions(-)
 create mode 100644 core/api/daemon/src/mill/api/daemon/internal/GroovyModuleApi.scala
 create mode 100644 libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
 create mode 100644 libs/groovylib/package.mill
 create mode 100644 libs/groovylib/src/mill/groovylib/GroovyMavenModule.scala
 create mode 100644 libs/groovylib/src/mill/groovylib/GroovyModule.scala
 create mode 100644 libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
 create mode 100644 libs/groovylib/src/mill/groovylib/TestGroovyMavenModule.scala
 create mode 100644 libs/groovylib/src/mill/groovylib/exports.scala
 create mode 100644 libs/groovylib/src/mill/groovylib/groovylib.scala
 create mode 100644 libs/groovylib/src/mill/groovylib/publish/exports.scala
 create mode 100644 libs/groovylib/test/resources/hello-groovy/main/script/src/HelloScript.groovy
 create mode 100644 libs/groovylib/test/resources/hello-groovy/main/spock/src/SpockTest.groovy
 create mode 100644 libs/groovylib/test/resources/hello-groovy/main/src/Hello.groovy
 create mode 100644 libs/groovylib/test/resources/hello-groovy/main/staticcompile/src/HelloStatic.groovy
 create mode 100644 libs/groovylib/test/resources/hello-groovy/main/test/src/HelloTest.groovy
 create mode 100644 libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
 create mode 100644 libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala

diff --git a/core/api/daemon/src/mill/api/daemon/internal/GroovyModuleApi.scala b/core/api/daemon/src/mill/api/daemon/internal/GroovyModuleApi.scala
new file mode 100644
index 000000000000..c64a187cfb27
--- /dev/null
+++ b/core/api/daemon/src/mill/api/daemon/internal/GroovyModuleApi.scala
@@ -0,0 +1,3 @@
+package mill.api.daemon.internal
+
+trait GroovyModuleApi extends JavaModuleApi
diff --git a/core/api/daemon/src/mill/api/daemon/internal/bsp/BspModuleApi.scala b/core/api/daemon/src/mill/api/daemon/internal/bsp/BspModuleApi.scala
index df66de24649c..43ea186bd958 100644
--- a/core/api/daemon/src/mill/api/daemon/internal/bsp/BspModuleApi.scala
+++ b/core/api/daemon/src/mill/api/daemon/internal/bsp/BspModuleApi.scala
@@ -15,6 +15,7 @@ object BspModuleApi {
     val Java = "java"
     val Scala = "scala"
     val Kotlin = "kotlin"
+    val Groovy = "groovy"
   }
 
   /** Used to define the [[BspBuildTarget.tags]] field. */
diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
new file mode 100644
index 000000000000..9e4a6c5cf4fc
--- /dev/null
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
@@ -0,0 +1,12 @@
+package mill.groovylib.worker.api
+
+import mill.api.TaskCtx
+import mill.api.Result
+import mill.javalib.api.CompilationResult
+
+trait GroovyWorker {
+
+  def compile(sourceFiles: Seq[os.Path], classpath: Seq[os.Path], outputDir: os.Path)(implicit
+      ctx: TaskCtx
+  ): Result[CompilationResult]
+}
diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
new file mode 100644
index 000000000000..e8b390db59d3
--- /dev/null
+++ b/libs/groovylib/package.mill
@@ -0,0 +1,50 @@
+package build.libs.groovylib
+
+// imports
+import mill.*
+import mill.contrib.buildinfo.BuildInfo
+import mill.scalalib.*
+import millbuild.*
+
+object `package` extends MillPublishScalaModule with BuildInfo {
+
+  def moduleDeps = Seq(build.libs.javalib, build.libs.javalib.testrunner, api)
+  def localTestExtraModules =
+    super.localTestExtraModules ++ Seq(worker)
+
+  def buildInfoPackageName = "mill.groovylib"
+  def buildInfoObjectName = "Versions"
+  def buildInfoMembers = Seq(
+    BuildInfo.Value("groovyVersion", Deps.groovyVersion, "Version of Groovy")
+  )
+
+  trait MillGroovyModule extends MillPublishScalaModule {
+    override def javacOptions = super.javacOptions() ++ {
+      val release =
+        if (scala.util.Properties.isJavaAtLeast(11)) Seq("-release", "8")
+        else Seq("-source", "1.8", "-target", "1.8")
+      release ++ Seq("-encoding", "UTF-8", "-deprecation")
+    }
+  }
+
+  object api extends MillGroovyModule {
+    def moduleDeps = Seq(build.libs.javalib.testrunner)
+
+    override def compileMvnDeps: T[Seq[Dep]] = Seq(
+      Deps.osLib
+    )
+  }
+
+  object worker extends MillGroovyModule {
+    override def compileModuleDeps = Seq(api)
+
+    def mandatoryMvnDeps = Seq.empty[Dep]
+
+    override def compileMvnDeps: T[Seq[Dep]] =
+      super.mandatoryMvnDeps() ++ Seq(
+        Deps.osLib,
+        Deps.groovyCompiler
+      )
+  }
+
+}
diff --git a/libs/groovylib/src/mill/groovylib/GroovyMavenModule.scala b/libs/groovylib/src/mill/groovylib/GroovyMavenModule.scala
new file mode 100644
index 000000000000..bfcabb3bee9e
--- /dev/null
+++ b/libs/groovylib/src/mill/groovylib/GroovyMavenModule.scala
@@ -0,0 +1,20 @@
+package mill.groovylib
+
+import mill.Task
+import mill.javalib.MavenModule
+
+/**
+ * A [[GroovyModule]] with a Maven compatible directory layout:
+ * `src/main/groovy`, `src/main/resources`, etc.
+ */
+trait GroovyMavenModule extends GroovyModule with MavenModule {
+  private def sources0 = Task.Sources("src/main/groovy")
+  override def sources = super.sources() ++ sources0()
+
+  trait GroovyMavenTests extends GroovyTests with MavenTests {
+    override def sources = Task.Sources(
+      moduleDir / "src" / testModuleName / "java",
+      moduleDir / "src" / testModuleName / "groovy"
+    )
+  }
+}
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
new file mode 100644
index 000000000000..08ef7115e95c
--- /dev/null
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -0,0 +1,269 @@
+package mill
+package groovylib
+
+import mill.api.{ModuleRef, Result}
+import mill.javalib.api.CompilationResult
+import mill.javalib.api.JvmWorkerApi as PublicJvmWorkerApi
+import mill.api.daemon.internal.{CompileProblemReporter, GroovyModuleApi, internal}
+import mill.javalib.{Dep, JavaModule, JvmWorkerModule, Lib}
+import mill.*
+import mainargs.Flag
+import mill.api.daemon.internal.bsp.{BspBuildTarget, BspModuleApi}
+import mill.javalib.api.internal.{JavaCompilerOptions, JvmWorkerApi, ZincCompileJava}
+
+/**
+ * Core configuration required to compile a single Groovy module
+ */
+trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
+
+  /**
+   * The Groovy version to be used.
+   */
+  def groovyVersion: T[String]
+
+  /**
+   * The compiler language version. Default is derived from [[groovyVersion]].
+   */
+  def groovyLanguageVersion: T[String] = Task { groovyVersion().split("[.]").take(2).mkString(".") }
+
+  override def bomMvnDeps: T[Seq[Dep]] = super.bomMvnDeps() ++ Seq(
+    mvn"org.apache.groovy:groovy-bom:${groovyVersion()}"
+  )
+
+  /**
+   * All individual source files fed into the compiler.
+   */
+  override def allSourceFiles: T[Seq[PathRef]] = Task {
+    Lib.findSourceFiles(allSources(), Seq("groovy", "java")).map(PathRef(_))
+  }
+
+  /**
+   * All individual Java source files fed into the compiler.
+   * Subset of [[allSourceFiles]].
+   */
+  private def allJavaSourceFiles: T[Seq[PathRef]] = Task {
+    allSourceFiles().filter(_.path.ext.toLowerCase() == "java")
+  }
+
+  /**
+   * All individual Groovy source files fed into the compiler.
+   * Subset of [[allSourceFiles]].
+   */
+  private def allGroovySourceFiles: T[Seq[PathRef]] = Task {
+    allSourceFiles().filter(path => Seq("groovy").contains(path.path.ext.toLowerCase()))
+  }
+
+  /**
+   * The dependencies of this module.
+   * Defaults to add the groovy dependency matching the [[groovyVersion]].
+   */
+  override def mandatoryMvnDeps: T[Seq[Dep]] = Task {
+    super.mandatoryMvnDeps() ++ Seq(
+      mvn"org.apache.groovy:groovy:${groovyVersion()}"
+    )
+  }
+
+  private def jvmWorkerRef: ModuleRef[JvmWorkerModule] = jvmWorker
+
+  override def checkGradleModules: T[Boolean] = true
+
+  /**
+   * The Java classpath resembling the Groovy compiler.
+   * Default is derived from [[groovyCompilerMvnDeps]].
+   */
+  def groovyCompilerClasspath: T[Seq[PathRef]] = Task {
+    val deps = groovyCompilerMvnDeps() ++ Seq(
+      Dep.millProjectModule("mill-libs-groovylib-worker")
+    )
+    defaultResolver().classpath(
+      deps,
+      resolutionParamsMapOpt = None
+    )
+  }
+
+  /**
+   * The Ivy/Coursier dependencies resembling the Groovy compiler.
+   *
+   * Default is derived from [[groovyCompilerVersion]].
+   */
+  def groovyCompilerMvnDeps: T[Seq[Dep]] = Task {
+    val gv = groovyVersion()
+
+    val compilerDep = mvn"org.apache.groovy:groovy:$gv"
+
+    Seq(compilerDep)
+  }
+
+  /**
+   * Compiler Plugin dependencies.
+   */
+  def groovyCompilerPluginMvnDeps: T[Seq[Dep]] = Task { Seq.empty[Dep] }
+
+  /**
+   * The resolved plugin jars
+   */
+  def groovyCompilerPluginJars: T[Seq[PathRef]] = Task {
+    val jars = defaultResolver().classpath(
+      groovycPluginMvnDeps()
+        // Don't resolve transitive jars
+        .map(d => d.exclude("*" -> "*")),
+      resolutionParamsMapOpt = None
+    )
+    jars.toSeq
+  }
+
+  /**
+   * Compiles all the sources to JVM class files.
+   */
+  override def compile: T[CompilationResult] = Task {
+    groovyCompileTask()()
+  }
+
+  /**
+   * The actual Groovy compile task (used by [[compile]] and [[groovycHelp]]).
+   */
+  protected def groovyCompileTask(): Task[CompilationResult] =
+    Task.Anon {
+      val ctx = Task.ctx()
+      val dest = ctx.dest
+      val classes = dest / "classes"
+      os.makeDir.all(classes)
+
+      val javaSourceFiles = allJavaSourceFiles().map(_.path)
+      val groovySourceFiles = allGroovySourceFiles().map(_.path)
+
+      val isGroovy = groovySourceFiles.nonEmpty
+      val isJava = javaSourceFiles.nonEmpty
+      val isMixed = isGroovy && isJava
+
+      val compileCp = compileClasspath().map(_.path).filter(os.exists)
+      val updateCompileOutput = upstreamCompileOutput()
+
+      def compileJava: Result[CompilationResult] = {
+        ctx.log.info(
+          s"Compiling ${javaSourceFiles.size} Java sources to ${classes} ..."
+        )
+        // The compile step is lazy, but its dependencies are not!
+        internalCompileJavaFiles(
+          worker = jvmWorkerRef().internalWorker(),
+          upstreamCompileOutput = updateCompileOutput,
+          javaSourceFiles = javaSourceFiles,
+          compileCp = compileCp,
+          javaHome = javaHome().map(_.path),
+          javacOptions = javacOptions(),
+          compileProblemReporter = ctx.reporter(hashCode),
+          reportOldProblems = internalReportOldProblems()
+        )
+      }
+
+      if (isMixed || isGroovy) {
+        ctx.log.info(
+          s"Compiling ${groovySourceFiles.size} Groovy sources to ${classes} ..."
+        )
+
+        val compileCp = compileClasspath().map(_.path).filter(os.exists)
+
+        val workerResult =
+          GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
+            _.compile(groovySourceFiles, compileCp, classes)
+          }
+
+        val analysisFile = dest / "groovy.analysis.dummy" // needed for mills CompilationResult
+        os.write(target = analysisFile, data = "", createFolders = true)
+
+        workerResult match {
+          case Result.Success(_) =>
+            val cr = CompilationResult(analysisFile, PathRef(classes))
+            if (!isJava) {
+              // pure Groovy project
+              cr
+            } else {
+              // also run Java compiler and use it's returned result
+              compileJava
+            }
+          case Result.Failure(reason) => Result.Failure(reason)
+        }
+      } else {
+        // it's Java only
+        compileJava
+      }
+    }
+
+  /**
+   * Additional Groovy compiler options to be used by [[compile]].
+   */
+  def groovycOptions: T[Seq[String]] = Task { Seq.empty[String] }
+
+  /**
+   * Aggregation of all the options passed to the Groovy compiler.
+   * In most cases, instead of overriding this target you want to override `groovycOptions` instead.
+   */
+  def allGroovycOptions: T[Seq[String]] = Task {
+    groovycOptions()
+  }
+
+  private[groovylib] def internalCompileJavaFiles(
+      worker: JvmWorkerApi,
+      upstreamCompileOutput: Seq[CompilationResult],
+      javaSourceFiles: Seq[os.Path],
+      compileCp: Seq[os.Path],
+      javaHome: Option[os.Path],
+      javacOptions: Seq[String],
+      compileProblemReporter: Option[CompileProblemReporter],
+      reportOldProblems: Boolean
+  )(implicit ctx: PublicJvmWorkerApi.Ctx): Result[CompilationResult] = {
+    val jOpts = JavaCompilerOptions(javacOptions)
+    worker.compileJava(
+      ZincCompileJava(
+        upstreamCompileOutput = upstreamCompileOutput,
+        sources = javaSourceFiles,
+        compileClasspath = compileCp,
+        javacOptions = jOpts.compiler,
+        incrementalCompilation = true
+      ),
+      javaHome = javaHome,
+      javaRuntimeOptions = jOpts.runtime,
+      reporter = compileProblemReporter,
+      reportCachedProblems = reportOldProblems
+    )
+  }
+
+  private[groovylib] def internalReportOldProblems: Task[Boolean] = zincReportCachedProblems
+
+  @internal
+  override def bspBuildTarget: BspBuildTarget = super.bspBuildTarget.copy(
+    languageIds = Seq(
+      BspModuleApi.LanguageId.Java,
+      BspModuleApi.LanguageId.Groovy
+    ),
+    canCompile = true,
+    canRun = true
+  )
+
+  override def prepareOffline(all: Flag): Command[Seq[PathRef]] = Task.Command {
+    (
+      super.prepareOffline(all)() ++
+        groovyCompilerClasspath()
+    ).distinct
+  }
+
+  /**
+   * A test sub-module linked to its parent module best suited for unit-tests.
+   */
+  trait GroovyTests extends JavaTests with GroovyModule {
+
+    override def groovyLanguageVersion: T[String] = outer.groovyLanguageVersion()
+    override def groovyVersion: T[String] = Task { outer.groovyVersion() }
+    override def groovycPluginMvnDeps: T[Seq[Dep]] =
+      Task { outer.groovycPluginMvnDeps() }
+      // TODO: make Xfriend-path an explicit setting
+    override def groovycOptions: T[Seq[String]] = Task {
+      // FIXME
+      outer.groovycOptions().filterNot(_.startsWith("-Xcommon-sources")) ++
+        Seq(s"-Xfriend-paths=${outer.compile().classes.path.toString()}")
+    }
+  }
+
+}
+
+// TODO maybe an StandaloneGroovyTestsModule
diff --git a/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala b/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
new file mode 100644
index 000000000000..9ccdc7845054
--- /dev/null
+++ b/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
@@ -0,0 +1,40 @@
+package mill.groovylib
+
+import mill.*
+import mill.api.{Discover, ExternalModule, TaskCtx}
+import mill.groovylib.worker.api.GroovyWorker
+import mill.util.ClassLoaderCachedFactory
+
+class GroovyWorkerManager()(implicit ctx: TaskCtx)
+    extends ClassLoaderCachedFactory[GroovyWorker](ctx.jobs) {
+
+  def getValue(cl: ClassLoader) = GroovyWorkerManager.get(cl)
+}
+
+object GroovyWorkerManager extends ExternalModule {
+  def groovyWorker: Worker[GroovyWorkerManager] = Task.Worker {
+    new GroovyWorkerManager()
+  }
+
+  def get(toolsClassLoader: ClassLoader)(implicit ctx: TaskCtx): GroovyWorker = {
+    val className =
+      classOf[GroovyWorker].getPackage().getName().split("\\.").dropRight(1).mkString(
+        "."
+      ) + ".impl." + classOf[GroovyWorker].getSimpleName() + "Impl"
+
+    val impl = toolsClassLoader.loadClass(className)
+    val worker = impl.getConstructor().newInstance().asInstanceOf[GroovyWorker]
+    if (worker.getClass().getClassLoader() != toolsClassLoader) {
+      ctx.log.warn(
+        """Worker not loaded from worker classloader.
+          |You should not add the mill-groovy-worker JAR to the mill build classpath""".stripMargin
+      )
+    }
+    if (worker.getClass().getClassLoader() == classOf[GroovyWorker].getClassLoader()) {
+      ctx.log.warn("Worker classloader used to load interface and implementation")
+    }
+    worker
+  }
+
+  override protected def millDiscover: Discover = Discover[this.type]
+}
diff --git a/libs/groovylib/src/mill/groovylib/TestGroovyMavenModule.scala b/libs/groovylib/src/mill/groovylib/TestGroovyMavenModule.scala
new file mode 100644
index 000000000000..1ad30eb67678
--- /dev/null
+++ b/libs/groovylib/src/mill/groovylib/TestGroovyMavenModule.scala
@@ -0,0 +1,25 @@
+package mill.groovylib
+
+import mill.*
+
+/**
+ * A [[GroovyModule]] for tests with a Maven compatible directory layout:
+ * `src/test/groovy`, `src/test/resources`, etc.
+ * This is useful when only the tests are written in Groovy while the production code remains in Java or other.
+ *
+ * Requires an outer module (like JavaModule) otherwise [[moduleDir]] must be overridden manually.
+ */
+trait TestGroovyMavenModule extends GroovyMavenModule {
+
+  /**
+   * The name of this module's folder within `src/`: e.g. `src/test/`, `src/integration/`,
+   * etc. Defaults to the name of the module object, but can be overridden by users
+   */
+  def testModuleName: String = moduleCtx.segments.last.value
+
+  private def testSources = Task.Sources(moduleDir / os.up / "src" / testModuleName / "groovy")
+  override def sources: T[Seq[PathRef]] = testSources()
+
+  private def testResources = Task.Sources(moduleDir / os.up / "src" / testModuleName / "resources")
+  override def resources: T[Seq[PathRef]] = testResources()
+}
diff --git a/libs/groovylib/src/mill/groovylib/exports.scala b/libs/groovylib/src/mill/groovylib/exports.scala
new file mode 100644
index 000000000000..9657cb08d604
--- /dev/null
+++ b/libs/groovylib/src/mill/groovylib/exports.scala
@@ -0,0 +1,13 @@
+package mill.groovylib
+
+export mill.javalib.DepSyntax
+
+export mill.javalib.Dep
+
+export mill.javalib.TestModule
+
+export mill.javalib.PublishModule
+
+export mill.javalib.NativeImageModule
+
+export mill.javalib.JvmWorkerModule
diff --git a/libs/groovylib/src/mill/groovylib/groovylib.scala b/libs/groovylib/src/mill/groovylib/groovylib.scala
new file mode 100644
index 000000000000..436a35a541bd
--- /dev/null
+++ b/libs/groovylib/src/mill/groovylib/groovylib.scala
@@ -0,0 +1,7 @@
+package mill
+
+/**
+ * Groovy toolchain containing [[GroovyModule]] and other functionality related to building
+ * Groovy projects.
+ */
+package object groovylib
diff --git a/libs/groovylib/src/mill/groovylib/publish/exports.scala b/libs/groovylib/src/mill/groovylib/publish/exports.scala
new file mode 100644
index 000000000000..8224e34c4956
--- /dev/null
+++ b/libs/groovylib/src/mill/groovylib/publish/exports.scala
@@ -0,0 +1,35 @@
+package mill.groovylib.publish
+
+export mill.javalib.publish.Ivy
+
+export mill.javalib.publish.License
+
+export mill.javalib.publish.LocalIvyPublisher
+
+export mill.javalib.publish.LocalM2Publisher
+
+export mill.javalib.publish.Pom
+
+export mill.javalib.publish.PublishInfo
+
+export mill.javalib.publish.Artifact
+
+export mill.javalib.publish.Scope
+
+export mill.javalib.publish.Dependency
+
+export mill.javalib.publish.Developer
+
+export mill.javalib.publish.PomSettings
+
+export mill.javalib.publish.PackagingType
+
+export mill.javalib.publish.SonatypeHelpers
+export mill.javalib.publish.SonatypeHttpApi
+export mill.javalib.publish.SonatypePublisher
+
+export mill.javalib.publish.VersionControl
+
+export mill.javalib.publish.VersionControlConnection
+
+export mill.javalib.publish.VersionScheme
diff --git a/libs/groovylib/test/resources/hello-groovy/main/script/src/HelloScript.groovy b/libs/groovylib/test/resources/hello-groovy/main/script/src/HelloScript.groovy
new file mode 100644
index 000000000000..2a709b574b4e
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/main/script/src/HelloScript.groovy
@@ -0,0 +1,8 @@
+
+println "This is a Groovy Script"
+println getHelloString()
+
+static String getHelloString() {
+    return "Hello, world!"
+}
+
diff --git a/libs/groovylib/test/resources/hello-groovy/main/spock/src/SpockTest.groovy b/libs/groovylib/test/resources/hello-groovy/main/spock/src/SpockTest.groovy
new file mode 100644
index 000000000000..6a4ef42f4a76
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/main/spock/src/SpockTest.groovy
@@ -0,0 +1,21 @@
+package hello.spock
+
+import spock.lang.Specification
+import static hello.Hello.*
+
+class SpockTest extends Specification {
+
+    def "test succeeds"() {
+        expect:
+        getHelloString() == "Hello, world!"
+    }
+
+    def "sayHello to '#name' equals '#expected'"() {
+        expect:
+        sayHello(name) == expected
+
+        where:
+        name << ["Foo", "Bar"]
+        expected = "Hello, $name"
+    }
+}
diff --git a/libs/groovylib/test/resources/hello-groovy/main/src/Hello.groovy b/libs/groovylib/test/resources/hello-groovy/main/src/Hello.groovy
new file mode 100644
index 000000000000..c6d16c431c32
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/main/src/Hello.groovy
@@ -0,0 +1,16 @@
+package hello
+
+class Hello {
+
+    static String getHelloString() {
+        return "Hello, world!"
+    }
+
+    static String sayHello(String name){
+        return "Hello, $name"
+    }
+
+    static void main(String[] args) {
+        println(getHelloString())
+    }
+}
\ No newline at end of file
diff --git a/libs/groovylib/test/resources/hello-groovy/main/staticcompile/src/HelloStatic.groovy b/libs/groovylib/test/resources/hello-groovy/main/staticcompile/src/HelloStatic.groovy
new file mode 100644
index 000000000000..fe56e2263888
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/main/staticcompile/src/HelloStatic.groovy
@@ -0,0 +1,26 @@
+package hellostatic
+
+import groovy.transform.CompileStatic
+
+@CompileStatic
+class HelloStatic {
+
+    static void main(String[] args) {
+        def x = new Some("Hello World")
+        x.doStuff()
+    }
+}
+
+@CompileStatic
+class Some {
+    
+    private String toPrint;
+
+    Some(String toPrint){
+        this.toPrint = toPrint
+    }
+
+    void doStuff(){
+        println(toPrint)
+    }
+}
\ No newline at end of file
diff --git a/libs/groovylib/test/resources/hello-groovy/main/test/src/HelloTest.groovy b/libs/groovylib/test/resources/hello-groovy/main/test/src/HelloTest.groovy
new file mode 100644
index 000000000000..5d9833fe9585
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/main/test/src/HelloTest.groovy
@@ -0,0 +1,12 @@
+package hello.tests
+
+import hello.Hello
+import org.junit.jupiter.api.Test
+import static org.junit.jupiter.api.Assertions.assertEquals
+
+class HelloTest {
+    @Test
+    void testSuccess() {
+        assertEquals("Hello, world!", Hello.getHelloString())
+    }
+}
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
new file mode 100644
index 000000000000..3ec2314fedaa
--- /dev/null
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -0,0 +1,185 @@
+package mill
+package groovylib
+
+import mill.javalib.{JavaModule, MavenModule, TestModule}
+import mill.api.{ExecResult, Task}
+import mill.api.Discover
+import mill.testkit.{TestRootModule, UnitTester}
+import utest.*
+
+object HelloGroovyTests extends TestSuite {
+
+  val groovy4Version = "4.0.28"
+  val junit5Version = sys.props.getOrElse("TEST_JUNIT5_VERSION", "5.13.4")
+
+  object HelloGroovy extends TestRootModule {
+
+    lazy val millDiscover = Discover[this.type]
+
+    // needed for a special test where only the tests are written in Groovy while appcode remains Java
+    object `mixed-compile` extends JavaModule with MavenModule {
+
+      object `test` extends TestGroovyMavenModule with TestModule.Junit5 {
+
+        override def moduleDeps: Seq[JavaModule] = Seq(
+          HelloGroovy.`mixed-compile`, // TODO improve: TestOnly does not inherit outer deps
+        )
+
+        override def groovyVersion = groovy4Version
+        override def depManagement = Seq(
+          mvn"org.junit.jupiter:junit-jupiter-engine:$junit5Version"
+        )
+        override def jupiterVersion = junit5Version
+        override def junitPlatformVersion = "1.13.4"
+      }
+
+    }
+
+    trait Test extends GroovyModule {
+
+      override def mainClass = Some("hello.Hello")
+
+      object test extends GroovyTests with TestModule.Junit5 {
+
+        override def depManagement = Seq(
+          mvn"org.junit.jupiter:junit-jupiter-engine:5.13.4"
+        )
+
+        override def jupiterVersion = "5.13.4"
+        override def junitPlatformVersion = "1.13.4"
+      }
+
+      object script extends GroovyModule {
+        override def groovyVersion = "4.0.28"
+        override def mainClass = Some("HelloScript")
+      }
+
+      object staticcompile extends GroovyModule {
+        override def groovyVersion = "4.0.28"
+        override def mainClass = Some("hellostatic.HelloStatic")
+      }
+
+      object spock extends GroovyTests with TestModule.Junit5 {
+        override def junitPlatformVersion = "1.13.4"
+        def spockVersion: T[String] = "2.3-groovy-4.0"
+        override def groovyVersion = "4.0.28"
+
+        def bomMvnDeps = Seq(
+          mvn"org.junit:junit-bom:5.13.4",
+          mvn"org.apache.groovy:groovy-bom:${groovyVersion()}",
+          mvn"org.spockframework:spock-bom:${spockVersion()}"
+        )
+
+        def mvnDeps = Seq(
+          mvn"org.spockframework:spock-core"
+        )
+      }
+    }
+    object main extends Test {
+      override def groovyVersion: T[String] = groovy4Version
+    }
+  }
+
+  val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-groovy"
+
+  /**
+   * Compiles test files located within resources
+   */
+  def testEval() = UnitTester(HelloGroovy, resourcePath)
+
+  def tests: Tests = Tests {
+
+    def m = HelloGroovy.main
+    def mixed = HelloGroovy.`mixed-compile`
+
+    test("running a Groovy script") {
+      testEval().scoped { eval =>
+        val Right(_) = eval.apply(m.script.run()): @unchecked
+      }
+    }
+
+    test("compile & run Groovy module") {
+      testEval().scoped { eval =>
+        val Right(compiler) = eval.apply(m.groovyCompilerMvnDeps): @unchecked
+
+        assert(
+          compiler.value.map(_.dep.module)
+            .map(m => m.organization.value -> m.name.value)
+            .contains("org.apache.groovy" -> "groovy")
+        )
+
+        val Right(result) = eval.apply(m.compile): @unchecked
+
+        assert(
+          os.walk(result.value.classes.path).exists(_.last == "Hello.class")
+        )
+
+        val Right(_) = eval.apply(m.run()): @unchecked
+      }
+    }
+
+    test("compile & run Groovy JUnit5 test") {
+      testEval().scoped { eval =>
+
+        val Right(result) = eval.apply(m.test.compile): @unchecked
+
+        assert(
+          os.walk(result.value.classes.path).exists(_.last == "HelloTest.class")
+        )
+
+        val Right(discovered) = eval.apply(m.test.discoveredTestClasses): @unchecked
+        assert(discovered.value == Seq("hello.tests.HelloTest"))
+
+        val Right(_) = eval.apply(m.test.testForked()): @unchecked
+      }
+    }
+
+//    test("compiling & running a statically compiled Groovy") {
+//      testEval().scoped { eval =>
+//        val Right(_) = eval.apply(m.staticcompile.showMvnDepsTree()): @unchecked
+//        val Right(result) = eval.apply(m.staticcompile.compile): @unchecked
+//        assert(
+//          os.walk(result.value.classes.path).exists(_.last == "HelloStatic.class")
+//        )
+//        val Right(_) = eval.apply(m.staticcompile.run()): @unchecked
+//      }
+//    }
+
+    test("compile & run test-only Maven JUnit5 test") {
+      testEval().scoped { eval =>
+
+        val Right(resultCompile) = eval.apply(mixed.compile): @unchecked
+        assert(
+          os.walk(resultCompile.value.classes.path).exists(_.last == "Greeter.class")
+        )
+
+        val Right(_) = eval.apply(mixed.test.compile): @unchecked
+        val Right(discovered) = eval.apply(mixed.test.discoveredTestClasses): @unchecked
+        assert(discovered.value == Seq("tests.GreeterTests"))
+
+        val Right(_) = eval.apply(mixed.test.testForked()): @unchecked
+      }
+    }
+
+//    test("compile Spock test") {
+//      testEval().scoped { eval =>
+//
+//        val Right(result1) = eval.apply(m.spock.compile): @unchecked
+//        assert(
+//          os.walk(result1.value.classes.path).exists(_.last == "SpockTest.class")
+//        )
+//      }
+//    }
+
+//    test("run Spock test") {
+//      testEval().scoped { eval =>
+//
+//        val Right(discovered) = eval.apply(m.spock.discoveredTestClasses): @unchecked
+//        assert(discovered.value == Seq("hello.spock.SpockTest"))
+//
+//        val Right(_) = eval.apply(m.spock.testForked()): @unchecked
+//      }
+//    }
+
+  }
+}
diff --git a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
new file mode 100644
index 000000000000..2ea7f3e0dc80
--- /dev/null
+++ b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
@@ -0,0 +1,43 @@
+package mill.groovylib.worker.impl
+
+import mill.api.Result
+import mill.api.TaskCtx
+import mill.javalib.api.CompilationResult
+import mill.groovylib.worker.api.GroovyWorker
+import org.codehaus.groovy.control.{CompilationUnit, CompilerConfiguration, Phases}
+
+import scala.jdk.CollectionConverters.*
+import scala.util.Try
+
+class GroovyWorkerImpl extends GroovyWorker {
+
+  def compile(
+      sourceFiles: Seq[os.Path],
+      classpath: Seq[os.Path],
+      outputDir: os.Path
+  )(implicit
+      ctx: TaskCtx
+  ): Result[CompilationResult] = {
+
+    val config = new CompilerConfiguration()
+    config.setTargetDirectory(outputDir.toIO)
+    config.setClasspathList(classpath.map(_.toIO.getAbsolutePath).asJava)
+
+    val unit = new CompilationUnit(config)
+
+    // Add source files to compile
+    sourceFiles.foreach { sourceFile =>
+      unit.addSource(sourceFile.toIO)
+    }
+
+    return Try {
+      unit.compile(Phases.OUTPUT)
+
+      CompilationResult(outputDir, mill.api.PathRef(outputDir))
+    }.fold(
+      exception => Result.Failure(s"Groovy compilation failed: ${exception.getMessage}"),
+      result => Result.Success(result)
+    )
+  }
+
+}
diff --git a/libs/javalib/src/mill/javalib/TestModule.scala b/libs/javalib/src/mill/javalib/TestModule.scala
index 9f0a0a2fdb86..7c20b7e2ccaf 100644
--- a/libs/javalib/src/mill/javalib/TestModule.scala
+++ b/libs/javalib/src/mill/javalib/TestModule.scala
@@ -2,8 +2,7 @@ package mill.javalib
 
 import mill.T
 import mill.api.Result
-import mill.api.daemon.internal.TestModuleApi
-import mill.api.daemon.internal.TestReporter
+import mill.api.daemon.internal.{TestModuleApi, TestReporter}
 import mill.api.daemon.internal.bsp.{BspBuildTarget, BspModuleApi}
 import mill.api.PathRef
 import mill.api.Task
@@ -58,6 +57,7 @@ trait TestModule
    * - [[TestModule.Utest]]
    * - [[TestModule.Weaver]]
    * - [[TestModule.ZioTest]]
+   * - [[TestModule.Spock]]
    *
    * Most of these provide additional `xxxVersion` tasks, to manage the test framework dependencies for you.
    */
@@ -600,6 +600,41 @@ object TestModule {
     }
   }
 
+  /**
+   * TestModule that uses Spock Test Framework to run tests.
+   * You can override the [[spockTestVersion]] task or provide the Spock-dependency yourself.
+   */
+  trait Spock extends TestModule.Junit5 {
+
+    /** The Spock Test version to use, or the empty string, if you want to provide the Spock Test-dependency yourself. */
+    def spockVersion: T[String] = Task {
+      ""
+    }
+
+    /** The Groovy version to use, or the empty string, if you want to provide the Groovy Test-dependency yourself. */
+    def groovyVersion: T[String] = Task {
+      ""
+    }
+
+    override def mandatoryMvnDeps: T[Seq[Dep]] = Task {
+      super.mandatoryMvnDeps() ++
+        Seq(spockVersion())
+          .filter(!_.isBlank())
+          .flatMap(v =>
+            Seq(
+              mvn"org.spockframework:spock-core:${v.trim()}"
+            )
+          ) ++
+        Seq(groovyVersion())
+          .filter(!_.isBlank())
+          .flatMap(v =>
+            Seq(
+              mvn"org.apache.groovy:groovy:${v.trim()}"
+            )
+          )
+    }
+  }
+
   def handleResults(
       doneMsg: String,
       results: Seq[TestResult],
diff --git a/libs/kotlinlib/src/mill/kotlinlib/publish/exports.scala b/libs/kotlinlib/src/mill/kotlinlib/publish/exports.scala
index c0104ef760f2..8224e34c4956 100644
--- a/libs/kotlinlib/src/mill/kotlinlib/publish/exports.scala
+++ b/libs/kotlinlib/src/mill/kotlinlib/publish/exports.scala
@@ -1,4 +1,4 @@
-package mill.kotlinlib.publish
+package mill.groovylib.publish
 
 export mill.javalib.publish.Ivy
 
diff --git a/libs/kotlinlib/test/src/mill/kotlinlib/HelloKotlinTests.scala b/libs/kotlinlib/test/src/mill/kotlinlib/HelloKotlinTests.scala
index 8793905681e3..0e81d2b12114 100644
--- a/libs/kotlinlib/test/src/mill/kotlinlib/HelloKotlinTests.scala
+++ b/libs/kotlinlib/test/src/mill/kotlinlib/HelloKotlinTests.scala
@@ -40,6 +40,7 @@ object HelloKotlinTests extends TestSuite {
     object main extends Cross[KotlinVersionCross](crossMatrix)
 
     lazy val millDiscover = Discover[this.type]
+    println(millDiscover)
   }
 
   val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-kotlin"
diff --git a/libs/package.mill b/libs/package.mill
index 603b5a5e7c36..98b6a978bede 100644
--- a/libs/package.mill
+++ b/libs/package.mill
@@ -10,6 +10,7 @@ import millbuild.*
 object `package` extends MillStableScalaModule {
   def moduleDeps = Seq(
     build.libs.kotlinlib,
+    build.libs.groovylib,
     build.libs.androidlib,
     build.libs.scalajslib,
     build.libs.scalanativelib,
diff --git a/mill-build/src/millbuild/Deps.scala b/mill-build/src/millbuild/Deps.scala
index 05936b3b95e8..f1c344f291f5 100644
--- a/mill-build/src/millbuild/Deps.scala
+++ b/mill-build/src/millbuild/Deps.scala
@@ -197,6 +197,8 @@ object Deps {
   val kotlinBuildToolsApi = mvn"org.jetbrains.kotlin:kotlin-build-tools-api:$kotlinVersion"
   val kotlinBuildToolsImpl = mvn"org.jetbrains.kotlin:kotlin-build-tools-impl:$kotlinVersion"
   val kotlinStdlib = mvn"org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion"
+  val groovyVersion = "4.0.28"
+  val groovyCompiler = mvn"org.apache.groovy:groovy:$groovyVersion"
 
   /** Used for the `mill init` from a Maven project. */
   object MavenInit {

From 51d62665c178257c31c7d2bdbf0a5be9adb344d1 Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Thu, 11 Sep 2025 21:27:18 +0200
Subject: [PATCH 02/23] adding more test cases and fixing classloader issue
 during groovy compile which also fixed spock not being executed

---
 libs/groovylib/package.mill                   |  6 +-
 .../src/mill/groovylib/GroovyModule.scala     | 53 +++++----------
 .../mill/groovylib/GroovyWorkerManager.scala  |  1 +
 .../joint-compile/src/GroovyGreeter.groovy    | 20 ++++++
 .../joint-compile/src/JavaMain.java           | 12 ++++
 .../joint-compile/src/JavaPrinter.java        |  7 ++
 .../main/script/src/HelloScript.groovy        |  3 +-
 .../src/mill/groovylib/HelloGroovyTests.scala | 68 ++++++++-----------
 .../worker/impl/GroovyWorkerImpl.scala        | 19 ++++--
 9 files changed, 100 insertions(+), 89 deletions(-)
 create mode 100644 libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy
 create mode 100644 libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java
 create mode 100644 libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaPrinter.java

diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index e8b390db59d3..bf7ee642f9a7 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -1,6 +1,5 @@
 package build.libs.groovylib
 
-// imports
 import mill.*
 import mill.contrib.buildinfo.BuildInfo
 import mill.scalalib.*
@@ -20,10 +19,7 @@ object `package` extends MillPublishScalaModule with BuildInfo {
 
   trait MillGroovyModule extends MillPublishScalaModule {
     override def javacOptions = super.javacOptions() ++ {
-      val release =
-        if (scala.util.Properties.isJavaAtLeast(11)) Seq("-release", "8")
-        else Seq("-source", "1.8", "-target", "1.8")
-      release ++ Seq("-encoding", "UTF-8", "-deprecation")
+      Seq("-release", "8", "-encoding", "UTF-8", "-deprecation")
     }
   }
 
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 08ef7115e95c..4d8df7301af9 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -26,9 +26,8 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    */
   def groovyLanguageVersion: T[String] = Task { groovyVersion().split("[.]").take(2).mkString(".") }
 
-  override def bomMvnDeps: T[Seq[Dep]] = super.bomMvnDeps() ++ Seq(
-    mvn"org.apache.groovy:groovy-bom:${groovyVersion()}"
-  )
+  override def bomMvnDeps: T[Seq[Dep]] = super.bomMvnDeps() ++
+    Seq(mvn"org.apache.groovy:groovy-bom:${groovyVersion()}")
 
   /**
    * All individual source files fed into the compiler.
@@ -58,12 +57,15 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    * Defaults to add the groovy dependency matching the [[groovyVersion]].
    */
   override def mandatoryMvnDeps: T[Seq[Dep]] = Task {
-    super.mandatoryMvnDeps() ++ Seq(
-      mvn"org.apache.groovy:groovy:${groovyVersion()}"
-    )
+    super.mandatoryMvnDeps()
+    ++
+      groovyCompilerMvnDeps()
+//    Seq(
+//      mvn"org.apache.groovy:groovy:${groovyVersion()}"
+//    )
   }
 
-  private def jvmWorkerRef: ModuleRef[JvmWorkerModule] = jvmWorker
+  def jvmWorkerRef: ModuleRef[JvmWorkerModule] = jvmWorker
 
   override def checkGradleModules: T[Boolean] = true
 
@@ -89,7 +91,8 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
   def groovyCompilerMvnDeps: T[Seq[Dep]] = Task {
     val gv = groovyVersion()
 
-    val compilerDep = mvn"org.apache.groovy:groovy:$gv"
+    val compilerDep = mvn"org.apache.groovy:groovy-all:$gv"
+//    val annotationDep = mvn"org.codehaus.groovy:groovy-all-annotations:$gv"
 
     Seq(compilerDep)
   }
@@ -104,9 +107,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    */
   def groovyCompilerPluginJars: T[Seq[PathRef]] = Task {
     val jars = defaultResolver().classpath(
-      groovycPluginMvnDeps()
-        // Don't resolve transitive jars
-        .map(d => d.exclude("*" -> "*")),
+      allMvnDeps(),
       resolutionParamsMapOpt = None
     )
     jars.toSeq
@@ -122,6 +123,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
   /**
    * The actual Groovy compile task (used by [[compile]] and [[groovycHelp]]).
    */
+  // TODO joint compilation: generate groovy-stubs -> compile java -> compile groovy -> delete stubs (or keep for debugging)
   protected def groovyCompileTask(): Task[CompilationResult] =
     Task.Anon {
       val ctx = Task.ctx()
@@ -152,7 +154,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
           javaHome = javaHome().map(_.path),
           javacOptions = javacOptions(),
           compileProblemReporter = ctx.reporter(hashCode),
-          reportOldProblems = internalReportOldProblems()
+          reportOldProblems = zincReportCachedProblems()
         )
       }
 
@@ -189,18 +191,6 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
       }
     }
 
-  /**
-   * Additional Groovy compiler options to be used by [[compile]].
-   */
-  def groovycOptions: T[Seq[String]] = Task { Seq.empty[String] }
-
-  /**
-   * Aggregation of all the options passed to the Groovy compiler.
-   * In most cases, instead of overriding this target you want to override `groovycOptions` instead.
-   */
-  def allGroovycOptions: T[Seq[String]] = Task {
-    groovycOptions()
-  }
 
   private[groovylib] def internalCompileJavaFiles(
       worker: JvmWorkerApi,
@@ -228,8 +218,6 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
     )
   }
 
-  private[groovylib] def internalReportOldProblems: Task[Boolean] = zincReportCachedProblems
-
   @internal
   override def bspBuildTarget: BspBuildTarget = super.bspBuildTarget.copy(
     languageIds = Seq(
@@ -254,16 +242,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
 
     override def groovyLanguageVersion: T[String] = outer.groovyLanguageVersion()
     override def groovyVersion: T[String] = Task { outer.groovyVersion() }
-    override def groovycPluginMvnDeps: T[Seq[Dep]] =
-      Task { outer.groovycPluginMvnDeps() }
-      // TODO: make Xfriend-path an explicit setting
-    override def groovycOptions: T[Seq[String]] = Task {
-      // FIXME
-      outer.groovycOptions().filterNot(_.startsWith("-Xcommon-sources")) ++
-        Seq(s"-Xfriend-paths=${outer.compile().classes.path.toString()}")
-    }
+    override def bomMvnDeps: T[Seq[Dep]] = outer.bomMvnDeps()
+    override def mandatoryMvnDeps: Task.Simple[Seq[Dep]] = outer.mandatoryMvnDeps
   }
-
 }
-
-// TODO maybe an StandaloneGroovyTestsModule
diff --git a/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala b/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
index 9ccdc7845054..292d5290dd4b 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
@@ -17,6 +17,7 @@ object GroovyWorkerManager extends ExternalModule {
   }
 
   def get(toolsClassLoader: ClassLoader)(implicit ctx: TaskCtx): GroovyWorker = {
+    // TODO why not use ServiceLoader...investigate
     val className =
       classOf[GroovyWorker].getPackage().getName().split("\\.").dropRight(1).mkString(
         "."
diff --git a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy
new file mode 100644
index 000000000000..f23aee4b2224
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy
@@ -0,0 +1,20 @@
+package jointcompile
+
+import jointCompile.JavaPrinter
+
+class GroovyGreeter{
+
+    private final String toGreet;
+    private final JavaPrinter printer;
+
+    GroovyGreeter(String toGreet){
+        this.toGreet = toGreet
+        this.printer = new JavaPrinter()
+    }
+
+
+    void greet(){
+        printer.print("Hello $toGreet");
+    }
+
+}
\ No newline at end of file
diff --git a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java
new file mode 100644
index 000000000000..14ae5384840d
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java
@@ -0,0 +1,12 @@
+package jointcompile;
+
+import jointcompile.GroovyGreeter;
+
+
+public class JavaMain {
+
+  public static void main(String[] args) {
+    var greeter = new GroovyGreeter("JointCompile");
+    greeter.greet();
+  }
+}
diff --git a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaPrinter.java b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaPrinter.java
new file mode 100644
index 000000000000..eb6dcfd64e19
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaPrinter.java
@@ -0,0 +1,7 @@
+package jointcompile;
+
+public class JavaPrinter {
+  public void print(String s) {
+    System.out.println(s);
+  }
+}
diff --git a/libs/groovylib/test/resources/hello-groovy/main/script/src/HelloScript.groovy b/libs/groovylib/test/resources/hello-groovy/main/script/src/HelloScript.groovy
index 2a709b574b4e..ccdd2a9a93e9 100644
--- a/libs/groovylib/test/resources/hello-groovy/main/script/src/HelloScript.groovy
+++ b/libs/groovylib/test/resources/hello-groovy/main/script/src/HelloScript.groovy
@@ -1,8 +1,7 @@
 
-println "This is a Groovy Script"
 println getHelloString()
 
 static String getHelloString() {
-    return "Hello, world!"
+    return "Hello, Scripting!"
 }
 
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index 3ec2314fedaa..77a65bf2d01c 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -35,16 +35,18 @@ object HelloGroovyTests extends TestSuite {
 
     }
 
+    object `joint-compile` extends GroovyModule {
+      override def groovyVersion: T[String] = groovy4Version
+    }
+
     trait Test extends GroovyModule {
 
       override def mainClass = Some("hello.Hello")
 
       object test extends GroovyTests with TestModule.Junit5 {
-
         override def depManagement = Seq(
           mvn"org.junit.jupiter:junit-jupiter-engine:5.13.4"
         )
-
         override def jupiterVersion = "5.13.4"
         override def junitPlatformVersion = "1.13.4"
       }
@@ -100,14 +102,6 @@ object HelloGroovyTests extends TestSuite {
 
     test("compile & run Groovy module") {
       testEval().scoped { eval =>
-        val Right(compiler) = eval.apply(m.groovyCompilerMvnDeps): @unchecked
-
-        assert(
-          compiler.value.map(_.dep.module)
-            .map(m => m.organization.value -> m.name.value)
-            .contains("org.apache.groovy" -> "groovy")
-        )
-
         val Right(result) = eval.apply(m.compile): @unchecked
 
         assert(
@@ -134,16 +128,15 @@ object HelloGroovyTests extends TestSuite {
       }
     }
 
-//    test("compiling & running a statically compiled Groovy") {
-//      testEval().scoped { eval =>
-//        val Right(_) = eval.apply(m.staticcompile.showMvnDepsTree()): @unchecked
-//        val Right(result) = eval.apply(m.staticcompile.compile): @unchecked
-//        assert(
-//          os.walk(result.value.classes.path).exists(_.last == "HelloStatic.class")
-//        )
-//        val Right(_) = eval.apply(m.staticcompile.run()): @unchecked
-//      }
-//    }
+    test("compiling & running a statically compiled Groovy") {
+      testEval().scoped { eval =>
+        val Right(result) = eval.apply(m.staticcompile.compile): @unchecked
+        assert(
+          os.walk(result.value.classes.path).exists(_.last == "HelloStatic.class")
+        )
+        val Right(_) = eval.apply(m.staticcompile.run()): @unchecked
+      }
+    }
 
     test("compile & run test-only Maven JUnit5 test") {
       testEval().scoped { eval =>
@@ -161,25 +154,22 @@ object HelloGroovyTests extends TestSuite {
       }
     }
 
-//    test("compile Spock test") {
-//      testEval().scoped { eval =>
-//
-//        val Right(result1) = eval.apply(m.spock.compile): @unchecked
-//        assert(
-//          os.walk(result1.value.classes.path).exists(_.last == "SpockTest.class")
-//        )
-//      }
-//    }
-
-//    test("run Spock test") {
-//      testEval().scoped { eval =>
-//
-//        val Right(discovered) = eval.apply(m.spock.discoveredTestClasses): @unchecked
-//        assert(discovered.value == Seq("hello.spock.SpockTest"))
-//
-//        val Right(_) = eval.apply(m.spock.testForked()): @unchecked
-//      }
-//    }
+    test("compile & run Spock test") {
+      testEval().scoped { eval =>
+
+        val Right(result1) = eval.apply(m.spock.compile): @unchecked
+        assert(
+          os.walk(result1.value.classes.path).exists(_.last == "SpockTest.class")
+        )
+
+        val Right(discovered) = eval.apply(m.spock.discoveredTestClasses): @unchecked
+        assert(discovered.value == Seq("hello.spock.SpockTest"))
+
+        val Right(_) = eval.apply(m.spock.testForked()): @unchecked
+      }
+    }
+
+
 
   }
 }
diff --git a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
index 2ea7f3e0dc80..cd7e26d06cf9 100644
--- a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
+++ b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
@@ -1,5 +1,6 @@
 package mill.groovylib.worker.impl
 
+import groovy.lang.GroovyClassLoader
 import mill.api.Result
 import mill.api.TaskCtx
 import mill.javalib.api.CompilationResult
@@ -22,22 +23,28 @@ class GroovyWorkerImpl extends GroovyWorker {
     val config = new CompilerConfiguration()
     config.setTargetDirectory(outputDir.toIO)
     config.setClasspathList(classpath.map(_.toIO.getAbsolutePath).asJava)
+    // TODO
+//    config.setDisabledGlobalASTTransformations()
+//    config.setJointCompilationOptions()
+//    config.setSourceEncoding()
+
+    // we need to set the classloader for groovy to use the worker classloader
+    val parentCl: ClassLoader = this.getClass.getClassLoader
+    // config in the GroovyClassLoader is needed when the CL itself is compiling classes
+    val gcl = new GroovyClassLoader(parentCl, config)
+    // config for actual compilation
+    val unit = new CompilationUnit(config, null, gcl)
 
-    val unit = new CompilationUnit(config)
-
-    // Add source files to compile
     sourceFiles.foreach { sourceFile =>
       unit.addSource(sourceFile.toIO)
     }
 
-    return Try {
+    Try {
       unit.compile(Phases.OUTPUT)
-
       CompilationResult(outputDir, mill.api.PathRef(outputDir))
     }.fold(
       exception => Result.Failure(s"Groovy compilation failed: ${exception.getMessage}"),
       result => Result.Success(result)
     )
   }
-
 }

From 4bcb5b198c912551791e8c02c1033e12771b1839 Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Fri, 12 Sep 2025 13:12:03 +0200
Subject: [PATCH 03/23] improve test-only-groovy to not rely on an existing
 outer module

---
 .../JavaMavenModuleWithGroovyTests.scala      | 16 ++++++++++++
 .../groovylib/TestGroovyMavenModule.scala     | 25 -------------------
 .../src/mill/groovylib/exports.scala          |  4 +++
 .../joint-compile/src/GroovyGreeter.groovy    |  2 --
 .../joint-compile/src/JavaMain.java           |  3 ---
 5 files changed, 20 insertions(+), 30 deletions(-)
 create mode 100644 libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
 delete mode 100644 libs/groovylib/src/mill/groovylib/TestGroovyMavenModule.scala

diff --git a/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala b/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
new file mode 100644
index 000000000000..c7018dcca885
--- /dev/null
+++ b/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
@@ -0,0 +1,16 @@
+package mill.groovylib
+
+import mill.*
+import mill.javalib.{JavaModule, MavenModule}
+
+/**
+ * Convenience trait for projects using Java for production and Groovy for tests in a Maven setup
+ */
+trait JavaMavenModuleWithGroovyTests extends JavaModule with MavenModule {
+
+  trait GroovyMavenTests extends JavaTests with MavenTests with GroovyModule {
+    private def groovyTestSources = Task.Sources(moduleDir / "src" / testModuleName / "groovy")
+    override def sources: T[Seq[PathRef]] = super[MavenTests].sources() ++ groovyTestSources()
+    override def resources: T[Seq[PathRef]] = super[MavenTests].resources()
+  }
+}
diff --git a/libs/groovylib/src/mill/groovylib/TestGroovyMavenModule.scala b/libs/groovylib/src/mill/groovylib/TestGroovyMavenModule.scala
deleted file mode 100644
index 1ad30eb67678..000000000000
--- a/libs/groovylib/src/mill/groovylib/TestGroovyMavenModule.scala
+++ /dev/null
@@ -1,25 +0,0 @@
-package mill.groovylib
-
-import mill.*
-
-/**
- * A [[GroovyModule]] for tests with a Maven compatible directory layout:
- * `src/test/groovy`, `src/test/resources`, etc.
- * This is useful when only the tests are written in Groovy while the production code remains in Java or other.
- *
- * Requires an outer module (like JavaModule) otherwise [[moduleDir]] must be overridden manually.
- */
-trait TestGroovyMavenModule extends GroovyMavenModule {
-
-  /**
-   * The name of this module's folder within `src/`: e.g. `src/test/`, `src/integration/`,
-   * etc. Defaults to the name of the module object, but can be overridden by users
-   */
-  def testModuleName: String = moduleCtx.segments.last.value
-
-  private def testSources = Task.Sources(moduleDir / os.up / "src" / testModuleName / "groovy")
-  override def sources: T[Seq[PathRef]] = testSources()
-
-  private def testResources = Task.Sources(moduleDir / os.up / "src" / testModuleName / "resources")
-  override def resources: T[Seq[PathRef]] = testResources()
-}
diff --git a/libs/groovylib/src/mill/groovylib/exports.scala b/libs/groovylib/src/mill/groovylib/exports.scala
index 9657cb08d604..89d445c8033c 100644
--- a/libs/groovylib/src/mill/groovylib/exports.scala
+++ b/libs/groovylib/src/mill/groovylib/exports.scala
@@ -4,6 +4,10 @@ export mill.javalib.DepSyntax
 
 export mill.javalib.Dep
 
+export mill.javalib.JavaModule
+
+export mill.javalib.MavenModule
+
 export mill.javalib.TestModule
 
 export mill.javalib.PublishModule
diff --git a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy
index f23aee4b2224..d876ed9310c3 100644
--- a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy
+++ b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy
@@ -1,7 +1,5 @@
 package jointcompile
 
-import jointCompile.JavaPrinter
-
 class GroovyGreeter{
 
     private final String toGreet;
diff --git a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java
index 14ae5384840d..6522149af6c4 100644
--- a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java
+++ b/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java
@@ -1,8 +1,5 @@
 package jointcompile;
 
-import jointcompile.GroovyGreeter;
-
-
 public class JavaMain {
 
   public static void main(String[] args) {

From 45dfd9bc69da10af42c95c81f4bc43cef64d01ee Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Mon, 15 Sep 2025 11:03:25 +0200
Subject: [PATCH 04/23] 3-stage compile to support Groovy <-> Java cycles

---
 .../groovylib/worker/api/GroovyWorker.scala   | 27 +++++-
 libs/groovylib/package.mill                   |  2 +-
 .../src/mill/groovylib/GroovyModule.scala     | 85 +++++++------------
 .../src/test/groovy/HelloMavenTestOnly.groovy | 12 +++
 .../src/mill/groovylib/HelloGroovyTests.scala | 54 +++++++-----
 .../worker/impl/GroovyWorkerImpl.scala        | 50 ++++++++++-
 .../javalib/src/mill/javalib/TestModule.scala | 15 ++--
 7 files changed, 157 insertions(+), 88 deletions(-)
 create mode 100644 libs/groovylib/test/resources/hello-groovy/groovy-tests/src/test/groovy/HelloMavenTestOnly.groovy

diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
index 9e4a6c5cf4fc..d92e90463e7a 100644
--- a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
@@ -4,9 +4,34 @@ import mill.api.TaskCtx
 import mill.api.Result
 import mill.javalib.api.CompilationResult
 
+/**
+ * Runs the actual compilation.
+ *
+ * Supports 3-stage compilation for Java <-> Groovy
+ * 1. compile Java stubs
+ * 2. compile Java sources (done externally)
+ * 3. compile Groovy sources
+ */
 trait GroovyWorker {
 
+  /**
+   * In a mixed setup this will compile the Groovy sources to Java stubs.
+   */
+  def compileGroovyStubs(
+      sourceFiles: Seq[os.Path],
+      classpath: Seq[os.Path],
+      outputDir: os.Path
+  )(implicit
+      ctx: TaskCtx
+  )
+      : Result[CompilationResult]
+
+  /**
+   * Compiles the Groovy sources. In a mixed setup this method assumes that the Java stubs
+   * are already present in the outputDir.
+   */
   def compile(sourceFiles: Seq[os.Path], classpath: Seq[os.Path], outputDir: os.Path)(implicit
       ctx: TaskCtx
-  ): Result[CompilationResult]
+  )
+      : Result[CompilationResult]
 }
diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index bf7ee642f9a7..483692461a40 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -8,7 +8,7 @@ import millbuild.*
 object `package` extends MillPublishScalaModule with BuildInfo {
 
   def moduleDeps = Seq(build.libs.javalib, build.libs.javalib.testrunner, api)
-  def localTestExtraModules =
+  def localTestExtraModules: Seq[MillJavaModule] =
     super.localTestExtraModules ++ Seq(worker)
 
   def buildInfoPackageName = "mill.groovylib"
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 4d8df7301af9..21d40f42e733 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -12,7 +12,9 @@ import mill.api.daemon.internal.bsp.{BspBuildTarget, BspModuleApi}
 import mill.javalib.api.internal.{JavaCompilerOptions, JvmWorkerApi, ZincCompileJava}
 
 /**
- * Core configuration required to compile a single Groovy module
+ * Core configuration required to compile a single Groovy module.
+ *
+ * Resolves
  */
 trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
 
@@ -33,7 +35,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    * All individual source files fed into the compiler.
    */
   override def allSourceFiles: T[Seq[PathRef]] = Task {
-    Lib.findSourceFiles(allSources(), Seq("groovy", "java")).map(PathRef(_))
+    allGroovySourceFiles() ++ allJavaSourceFiles()
   }
 
   /**
@@ -41,7 +43,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    * Subset of [[allSourceFiles]].
    */
   private def allJavaSourceFiles: T[Seq[PathRef]] = Task {
-    allSourceFiles().filter(_.path.ext.toLowerCase() == "java")
+    Lib.findSourceFiles(allSources(), Seq("java")).map(PathRef(_))
   }
 
   /**
@@ -49,20 +51,15 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    * Subset of [[allSourceFiles]].
    */
   private def allGroovySourceFiles: T[Seq[PathRef]] = Task {
-    allSourceFiles().filter(path => Seq("groovy").contains(path.path.ext.toLowerCase()))
+    Lib.findSourceFiles(allSources(), Seq("groovy")).map(PathRef(_))
   }
 
   /**
    * The dependencies of this module.
-   * Defaults to add the groovy dependency matching the [[groovyVersion]].
+   * Defaults to add the Groovy dependency matching the [[groovyVersion]].
    */
   override def mandatoryMvnDeps: T[Seq[Dep]] = Task {
-    super.mandatoryMvnDeps()
-    ++
-      groovyCompilerMvnDeps()
-//    Seq(
-//      mvn"org.apache.groovy:groovy:${groovyVersion()}"
-//    )
+    super.mandatoryMvnDeps() ++ groovyCompilerMvnDeps()
   }
 
   def jvmWorkerRef: ModuleRef[JvmWorkerModule] = jvmWorker
@@ -86,31 +83,11 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
   /**
    * The Ivy/Coursier dependencies resembling the Groovy compiler.
    *
-   * Default is derived from [[groovyCompilerVersion]].
+   * Default is derived from [[groovyVersion]].
    */
   def groovyCompilerMvnDeps: T[Seq[Dep]] = Task {
     val gv = groovyVersion()
-
-    val compilerDep = mvn"org.apache.groovy:groovy-all:$gv"
-//    val annotationDep = mvn"org.codehaus.groovy:groovy-all-annotations:$gv"
-
-    Seq(compilerDep)
-  }
-
-  /**
-   * Compiler Plugin dependencies.
-   */
-  def groovyCompilerPluginMvnDeps: T[Seq[Dep]] = Task { Seq.empty[Dep] }
-
-  /**
-   * The resolved plugin jars
-   */
-  def groovyCompilerPluginJars: T[Seq[PathRef]] = Task {
-    val jars = defaultResolver().classpath(
-      allMvnDeps(),
-      resolutionParamsMapOpt = None
-    )
-    jars.toSeq
+    Seq(mvn"org.apache.groovy:groovy:$gv")
   }
 
   /**
@@ -121,9 +98,8 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
   }
 
   /**
-   * The actual Groovy compile task (used by [[compile]] and [[groovycHelp]]).
+   * The actual Groovy compile task (used by [[compile]]).
    */
-  // TODO joint compilation: generate groovy-stubs -> compile java -> compile groovy -> delete stubs (or keep for debugging)
   protected def groovyCompileTask(): Task[CompilationResult] =
     Task.Anon {
       val ctx = Task.ctx()
@@ -143,9 +119,9 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
 
       def compileJava: Result[CompilationResult] = {
         ctx.log.info(
-          s"Compiling ${javaSourceFiles.size} Java sources to ${classes} ..."
+          s"Compiling ${javaSourceFiles.size} Java sources to $classes ..."
         )
-        // The compile step is lazy, but its dependencies are not!
+        // The compiler step is lazy, but its dependencies are not!
         internalCompileJavaFiles(
           worker = jvmWorkerRef().internalWorker(),
           upstreamCompileOutput = updateCompileOutput,
@@ -158,40 +134,43 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
         )
       }
 
+      if (isMixed) {
+        ctx.log.info("Compiling Groovy stubs for mixed compilation")
+
+        val workerStubResult =
+          GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
+            _.compileGroovyStubs(groovySourceFiles, compileCp, classes)
+          }
+        workerStubResult match {
+          case Result.Success(_) => compileJava
+          case Result.Failure(reason) => Result.Failure(reason)
+        }
+      }
+
       if (isMixed || isGroovy) {
         ctx.log.info(
-          s"Compiling ${groovySourceFiles.size} Groovy sources to ${classes} ..."
+          s"Compiling ${groovySourceFiles.size} Groovy sources to $classes ..."
         )
 
-        val compileCp = compileClasspath().map(_.path).filter(os.exists)
-
-        val workerResult =
+        val workerGroovyResult =
           GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
             _.compile(groovySourceFiles, compileCp, classes)
           }
 
+        // TODO figure out if there is a better way to do this
         val analysisFile = dest / "groovy.analysis.dummy" // needed for mills CompilationResult
         os.write(target = analysisFile, data = "", createFolders = true)
 
-        workerResult match {
+        workerGroovyResult match {
           case Result.Success(_) =>
-            val cr = CompilationResult(analysisFile, PathRef(classes))
-            if (!isJava) {
-              // pure Groovy project
-              cr
-            } else {
-              // also run Java compiler and use it's returned result
-              compileJava
-            }
+            CompilationResult(analysisFile, PathRef(classes))
           case Result.Failure(reason) => Result.Failure(reason)
         }
       } else {
-        // it's Java only
         compileJava
       }
     }
 
-
   private[groovylib] def internalCompileJavaFiles(
       worker: JvmWorkerApi,
       upstreamCompileOutput: Seq[CompilationResult],
@@ -236,7 +215,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
   }
 
   /**
-   * A test sub-module linked to its parent module best suited for unit-tests.
+   * A test submodule linked to its parent module best suited for unit-tests.
    */
   trait GroovyTests extends JavaTests with GroovyModule {
 
diff --git a/libs/groovylib/test/resources/hello-groovy/groovy-tests/src/test/groovy/HelloMavenTestOnly.groovy b/libs/groovylib/test/resources/hello-groovy/groovy-tests/src/test/groovy/HelloMavenTestOnly.groovy
new file mode 100644
index 000000000000..3f456065bfa4
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/groovy-tests/src/test/groovy/HelloMavenTestOnly.groovy
@@ -0,0 +1,12 @@
+package hello.maven.tests
+
+//import hello.Hello
+import org.junit.jupiter.api.Test
+import static org.junit.jupiter.api.Assertions.assertEquals
+
+class HelloMavenTestOnly {
+    @Test
+    void testSuccess() {
+        assertEquals(true, true)
+    }
+}
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index 77a65bf2d01c..9a3818f79227 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -1,8 +1,8 @@
 package mill
 package groovylib
 
-import mill.javalib.{JavaModule, MavenModule, TestModule}
-import mill.api.{ExecResult, Task}
+import mill.javalib.{JavaModule, TestModule}
+import mill.api.{Task}
 import mill.api.Discover
 import mill.testkit.{TestRootModule, UnitTester}
 import utest.*
@@ -17,12 +17,12 @@ object HelloGroovyTests extends TestSuite {
     lazy val millDiscover = Discover[this.type]
 
     // needed for a special test where only the tests are written in Groovy while appcode remains Java
-    object `mixed-compile` extends JavaModule with MavenModule {
+    object `groovy-tests` extends JavaMavenModuleWithGroovyTests {
 
-      object `test` extends TestGroovyMavenModule with TestModule.Junit5 {
+      object `test` extends GroovyMavenTests with TestModule.Junit5 {
 
         override def moduleDeps: Seq[JavaModule] = Seq(
-          HelloGroovy.`mixed-compile`, // TODO improve: TestOnly does not inherit outer deps
+          HelloGroovy.`groovy-tests`
         )
 
         override def groovyVersion = groovy4Version
@@ -37,6 +37,7 @@ object HelloGroovyTests extends TestSuite {
 
     object `joint-compile` extends GroovyModule {
       override def groovyVersion: T[String] = groovy4Version
+      override def mainClass = Some("jointcompile.JavaMain")
     }
 
     trait Test extends GroovyModule {
@@ -61,20 +62,16 @@ object HelloGroovyTests extends TestSuite {
         override def mainClass = Some("hellostatic.HelloStatic")
       }
 
-      object spock extends GroovyTests with TestModule.Junit5 {
+      object spock extends GroovyTests with TestModule.Spock {
         override def junitPlatformVersion = "1.13.4"
-        def spockVersion: T[String] = "2.3-groovy-4.0"
+        override def spockVersion = "2.3-groovy-4.0"
         override def groovyVersion = "4.0.28"
 
         def bomMvnDeps = Seq(
           mvn"org.junit:junit-bom:5.13.4",
-          mvn"org.apache.groovy:groovy-bom:${groovyVersion()}",
+//          mvn"org.apache.groovy:groovy-bom:${groovyVersion()}",
           mvn"org.spockframework:spock-bom:${spockVersion()}"
         )
-
-        def mvnDeps = Seq(
-          mvn"org.spockframework:spock-core"
-        )
       }
     }
     object main extends Test {
@@ -92,7 +89,14 @@ object HelloGroovyTests extends TestSuite {
   def tests: Tests = Tests {
 
     def m = HelloGroovy.main
-    def mixed = HelloGroovy.`mixed-compile`
+    def mixed = HelloGroovy.`groovy-tests`
+    def joint = HelloGroovy.`joint-compile`
+
+    test("running a Groovy script") {
+      testEval().scoped { eval =>
+        val Right(_) = eval.apply(m.script.run()): @unchecked
+      }
+    }
 
     test("running a Groovy script") {
       testEval().scoped { eval =>
@@ -128,7 +132,7 @@ object HelloGroovyTests extends TestSuite {
       }
     }
 
-    test("compiling & running a statically compiled Groovy") {
+    test("compile & run a statically compiled Groovy") {
       testEval().scoped { eval =>
         val Right(result) = eval.apply(m.staticcompile.compile): @unchecked
         assert(
@@ -138,17 +142,12 @@ object HelloGroovyTests extends TestSuite {
       }
     }
 
-    test("compile & run test-only Maven JUnit5 test") {
+    test("compile & test module (only test uses Groovy)") {
       testEval().scoped { eval =>
 
-        val Right(resultCompile) = eval.apply(mixed.compile): @unchecked
-        assert(
-          os.walk(resultCompile.value.classes.path).exists(_.last == "Greeter.class")
-        )
-
         val Right(_) = eval.apply(mixed.test.compile): @unchecked
         val Right(discovered) = eval.apply(mixed.test.discoveredTestClasses): @unchecked
-        assert(discovered.value == Seq("tests.GreeterTests"))
+        assert(discovered.value == Seq("hello.maven.tests.HelloMavenTestOnly"))
 
         val Right(_) = eval.apply(mixed.test.testForked()): @unchecked
       }
@@ -169,7 +168,20 @@ object HelloGroovyTests extends TestSuite {
       }
     }
 
+    test("compile joint (groovy <-> java cycle) & run") {
+      testEval().scoped { eval =>
+        val Right(result) = eval.apply(joint.compile): @unchecked
 
+        assert(
+          os.walk(result.value.classes.path).exists(_.last == "JavaPrinter.class")
+        )
+        assert(
+          os.walk(result.value.classes.path).exists(_.last == "GroovyGreeter.class")
+        )
+
+        val Right(_) = eval.apply(joint.run()): @unchecked
+      }
+    }
 
   }
 }
diff --git a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
index cd7e26d06cf9..391ac9a702dd 100644
--- a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
+++ b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
@@ -6,12 +6,48 @@ import mill.api.TaskCtx
 import mill.javalib.api.CompilationResult
 import mill.groovylib.worker.api.GroovyWorker
 import org.codehaus.groovy.control.{CompilationUnit, CompilerConfiguration, Phases}
+import org.codehaus.groovy.tools.javac.JavaStubCompilationUnit
+import os.Path
 
 import scala.jdk.CollectionConverters.*
 import scala.util.Try
 
 class GroovyWorkerImpl extends GroovyWorker {
 
+  override def compileGroovyStubs(
+      sourceFiles: Seq[Path],
+      classpath: Seq[Path],
+      outputDir: Path
+  )(implicit ctx: TaskCtx): Result[CompilationResult] = {
+    val config = new CompilerConfiguration()
+    config.setTargetDirectory(outputDir.toIO)
+    config.setClasspathList(classpath.map(_.toIO.getAbsolutePath).asJava)
+    config.setJointCompilationOptions(Map(
+      "stubDir" -> outputDir.toIO,
+      "keepStubs" -> false
+    ).asJava)
+
+    // we need to set the classloader for groovy to use the worker classloader
+    val parentCl: ClassLoader = this.getClass.getClassLoader
+    // config in the GroovyClassLoader is needed when the CL itself is compiling classes
+    val gcl = new GroovyClassLoader(parentCl, config)
+    // config for actual compilation
+    val stubUnit = JavaStubCompilationUnit(config, gcl)
+
+    sourceFiles.foreach { sourceFile =>
+      stubUnit.addSource(sourceFile.toIO)
+    }
+
+    Try {
+      stubUnit.compile(Phases.CONVERSION)
+      CompilationResult(outputDir, mill.api.PathRef(outputDir))
+    }.fold(
+      exception => Result.Failure(s"Groovy stub generation failed: ${exception.getMessage}"),
+      result => Result.Success(result)
+    )
+
+  }
+
   def compile(
       sourceFiles: Seq[os.Path],
       classpath: Seq[os.Path],
@@ -20,12 +56,13 @@ class GroovyWorkerImpl extends GroovyWorker {
       ctx: TaskCtx
   ): Result[CompilationResult] = {
 
+    val extendedClasspath = classpath :+ outputDir
+
     val config = new CompilerConfiguration()
     config.setTargetDirectory(outputDir.toIO)
-    config.setClasspathList(classpath.map(_.toIO.getAbsolutePath).asJava)
+    config.setClasspathList(extendedClasspath.map(_.toIO.getAbsolutePath).asJava)
     // TODO
 //    config.setDisabledGlobalASTTransformations()
-//    config.setJointCompilationOptions()
 //    config.setSourceEncoding()
 
     // we need to set the classloader for groovy to use the worker classloader
@@ -41,10 +78,19 @@ class GroovyWorkerImpl extends GroovyWorker {
 
     Try {
       unit.compile(Phases.OUTPUT)
+      removeAllJavaFiles(outputDir)
       CompilationResult(outputDir, mill.api.PathRef(outputDir))
     }.fold(
       exception => Result.Failure(s"Groovy compilation failed: ${exception.getMessage}"),
       result => Result.Success(result)
     )
   }
+
+  private def removeAllJavaFiles(outputDir: os.Path): Unit = {
+    if (os.exists(outputDir)) {
+      os.walk(outputDir)
+        .filter(_.ext == "java")
+        .foreach(os.remove)
+    }
+  }
 }
diff --git a/libs/javalib/src/mill/javalib/TestModule.scala b/libs/javalib/src/mill/javalib/TestModule.scala
index 7c20b7e2ccaf..24f1e9805df3 100644
--- a/libs/javalib/src/mill/javalib/TestModule.scala
+++ b/libs/javalib/src/mill/javalib/TestModule.scala
@@ -602,20 +602,22 @@ object TestModule {
 
   /**
    * TestModule that uses Spock Test Framework to run tests.
-   * You can override the [[spockTestVersion]] task or provide the Spock-dependency yourself.
+   * You can override the [[spockVersion]] task or provide the Spock dependency yourself.
    */
   trait Spock extends TestModule.Junit5 {
 
-    /** The Spock Test version to use, or the empty string, if you want to provide the Spock Test-dependency yourself. */
+    /** The Spock Test version to use, or the empty string, if you want to provide the Spock test dependency yourself. */
     def spockVersion: T[String] = Task {
       ""
     }
 
-    /** The Groovy version to use, or the empty string, if you want to provide the Groovy Test-dependency yourself. */
+    /** The Groovy version to use, or the empty string, if you want to provide the Groovy test dependency yourself. */
     def groovyVersion: T[String] = Task {
       ""
     }
 
+    // TODO currently bomMvnDeps not in JavaModuleBase so we cannot pull in the Spock-BOM
+
     override def mandatoryMvnDeps: T[Seq[Dep]] = Task {
       super.mandatoryMvnDeps() ++
         Seq(spockVersion())
@@ -624,13 +626,6 @@ object TestModule {
             Seq(
               mvn"org.spockframework:spock-core:${v.trim()}"
             )
-          ) ++
-        Seq(groovyVersion())
-          .filter(!_.isBlank())
-          .flatMap(v =>
-            Seq(
-              mvn"org.apache.groovy:groovy:${v.trim()}"
-            )
           )
     }
   }

From cacf2c7e5b296b8e23885fb845f85b500bc6bc4a Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Tue, 16 Sep 2025 15:21:30 +0200
Subject: [PATCH 05/23] manage BOMs in Tests

Starting with JUnit 5.12 and Spock 2.3 a BOM is available on Maven Central.
If the version matches the BOMs will be automatically added.

For JUnit, this has the effect that the platform-launcher is also managed in the BOM so it is actually not necessary to specify a platform-launcher-version. Hence the launcher is also added when the version is not set and the minimum version is met.
---
 libs/groovylib/package.mill                   |   2 +-
 .../src/mill/groovylib/GroovyModule.scala     |  13 ++-
 .../src/mill/groovylib/HelloGroovyTests.scala | 109 ++++++++++++++----
 .../javalib/src/mill/javalib/TestModule.scala |  65 +++++++++--
 .../src/mill/javalib/junit5/JUnit5Tests.scala |  62 +++++++++-
 5 files changed, 216 insertions(+), 35 deletions(-)

diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index 483692461a40..e9720db4ff65 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -7,7 +7,7 @@ import millbuild.*
 
 object `package` extends MillPublishScalaModule with BuildInfo {
 
-  def moduleDeps = Seq(build.libs.javalib, build.libs.javalib.testrunner, api)
+  def moduleDeps = Seq(build.libs.util, build.libs.javalib, build.libs.javalib.testrunner, api)
   def localTestExtraModules: Seq[MillJavaModule] =
     super.localTestExtraModules ++ Seq(worker)
 
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 21d40f42e733..284315fac4d2 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -10,6 +10,7 @@ import mill.*
 import mainargs.Flag
 import mill.api.daemon.internal.bsp.{BspBuildTarget, BspModuleApi}
 import mill.javalib.api.internal.{JavaCompilerOptions, JvmWorkerApi, ZincCompileJava}
+import mill.util.Version
 
 /**
  * Core configuration required to compile a single Groovy module.
@@ -28,8 +29,18 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    */
   def groovyLanguageVersion: T[String] = Task { groovyVersion().split("[.]").take(2).mkString(".") }
 
+  private def isGroovyBomAvailable: T[Boolean] = Task {
+    if (groovyVersion().isBlank) {
+      false
+    } else {
+      Version.isAtLeast(groovyVersion(), "4.0.26")(using Version.IgnoreQualifierOrdering)
+    }
+  }
+
   override def bomMvnDeps: T[Seq[Dep]] = super.bomMvnDeps() ++
-    Seq(mvn"org.apache.groovy:groovy-bom:${groovyVersion()}")
+    Seq(groovyVersion())
+      .filter(_.nonEmpty && isGroovyBomAvailable())
+      .map(v => mvn"org.apache.groovy:groovy-bom:$v")
 
   /**
    * All individual source files fed into the compiler.
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index 9a3818f79227..8a0e1be24db4 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -2,7 +2,7 @@ package mill
 package groovylib
 
 import mill.javalib.{JavaModule, TestModule}
-import mill.api.{Task}
+import mill.api.Task
 import mill.api.Discover
 import mill.testkit.{TestRootModule, UnitTester}
 import utest.*
@@ -11,6 +11,7 @@ object HelloGroovyTests extends TestSuite {
 
   val groovy4Version = "4.0.28"
   val junit5Version = sys.props.getOrElse("TEST_JUNIT5_VERSION", "5.13.4")
+  val spockGroovy4Version = "2.3-groovy-4.0"
 
   object HelloGroovy extends TestRootModule {
 
@@ -25,12 +26,8 @@ object HelloGroovyTests extends TestSuite {
           HelloGroovy.`groovy-tests`
         )
 
-        override def groovyVersion = groovy4Version
-        override def depManagement = Seq(
-          mvn"org.junit.jupiter:junit-jupiter-engine:$junit5Version"
-        )
-        override def jupiterVersion = junit5Version
-        override def junitPlatformVersion = "1.13.4"
+        override def groovyVersion: T[String] = groovy4Version
+        override def jupiterVersion: T[String] = junit5Version
       }
 
     }
@@ -40,38 +37,53 @@ object HelloGroovyTests extends TestSuite {
       override def mainClass = Some("jointcompile.JavaMain")
     }
 
+    object deps extends Module {
+
+      object groovyBom extends GroovyModule {
+        override def groovyVersion: T[String] = groovy4Version
+      }
+
+      object groovyNoBom extends GroovyModule {
+        // Groovy-BOM available starting with 4.0.26
+        override def groovyVersion: T[String] = "4.0.25"
+      }
+
+      object `spockBom` extends GroovyModule with TestModule.Spock {
+        override def spockVersion: T[String] = spockGroovy4Version
+        override def groovyVersion: T[String] = groovy4Version
+      }
+
+      object `spockNoBom` extends GroovyModule with TestModule.Spock {
+        // Groovy-BOM available starting with 2.3
+        override def spockVersion: T[String] = "2.2-groovy-4.0"
+        override def groovyVersion: T[String] = groovy4Version
+      }
+
+    }
+
     trait Test extends GroovyModule {
 
       override def mainClass = Some("hello.Hello")
 
       object test extends GroovyTests with TestModule.Junit5 {
-        override def depManagement = Seq(
-          mvn"org.junit.jupiter:junit-jupiter-engine:5.13.4"
-        )
-        override def jupiterVersion = "5.13.4"
+        override def jupiterVersion: T[String] = junit5Version
         override def junitPlatformVersion = "1.13.4"
       }
 
       object script extends GroovyModule {
-        override def groovyVersion = "4.0.28"
+        override def groovyVersion: T[String] = groovy4Version
         override def mainClass = Some("HelloScript")
       }
 
       object staticcompile extends GroovyModule {
-        override def groovyVersion = "4.0.28"
+        override def groovyVersion: T[String] = groovy4Version
         override def mainClass = Some("hellostatic.HelloStatic")
       }
 
       object spock extends GroovyTests with TestModule.Spock {
-        override def junitPlatformVersion = "1.13.4"
-        override def spockVersion = "2.3-groovy-4.0"
-        override def groovyVersion = "4.0.28"
-
-        def bomMvnDeps = Seq(
-          mvn"org.junit:junit-bom:5.13.4",
-//          mvn"org.apache.groovy:groovy-bom:${groovyVersion()}",
-          mvn"org.spockframework:spock-bom:${spockVersion()}"
-        )
+        override def jupiterVersion: T[String] = junit5Version
+        override def spockVersion: T[String] = spockGroovy4Version
+        override def groovyVersion: T[String] = groovy4Version
       }
     }
     object main extends Test {
@@ -91,6 +103,7 @@ object HelloGroovyTests extends TestSuite {
     def m = HelloGroovy.main
     def mixed = HelloGroovy.`groovy-tests`
     def joint = HelloGroovy.`joint-compile`
+    def deps = HelloGroovy.deps
 
     test("running a Groovy script") {
       testEval().scoped { eval =>
@@ -183,5 +196,57 @@ object HelloGroovyTests extends TestSuite {
       }
     }
 
+    test("dependency management") {
+
+      test("groovy") {
+
+        val groovyBom = mvn"org.apache.groovy:groovy-bom:$groovy4Version"
+
+        test("groovy bom is added when version is at least 4.0.26") {
+          testEval().scoped { eval =>
+            val Right(result) = eval.apply(deps.groovyBom.bomMvnDeps): @unchecked
+
+            assert(
+              result.value.contains(groovyBom)
+            )
+          }
+        }
+
+        test("groovy bom is NOT added when version is below 4.0.26") {
+          testEval().scoped { eval =>
+            val Right(result) = eval.apply(deps.groovyNoBom.bomMvnDeps): @unchecked
+
+            assert(
+              !result.value.contains(groovyBom)
+            )
+          }
+        }
+      }
+
+      test("spock") {
+
+        val spockBom = mvn"org.spockframework:spock-bom:$spockGroovy4Version"
+
+        test("spock bom is added when version is at least 2.3") {
+          testEval().scoped { eval =>
+            val Right(result) = eval.apply(deps.spockBom.bomMvnDeps): @unchecked
+
+            assert(
+              result.value.contains(spockBom)
+            )
+          }
+        }
+
+        test("spock bom is NOT added when version is below 2.3") {
+          testEval().scoped { eval =>
+            val Right(result) = eval.apply(deps.spockNoBom.bomMvnDeps): @unchecked
+
+            assert(
+              !result.value.contains(spockBom)
+            )
+          }
+        }
+      }
+    }
   }
 }
diff --git a/libs/javalib/src/mill/javalib/TestModule.scala b/libs/javalib/src/mill/javalib/TestModule.scala
index 24f1e9805df3..02d826dd0ade 100644
--- a/libs/javalib/src/mill/javalib/TestModule.scala
+++ b/libs/javalib/src/mill/javalib/TestModule.scala
@@ -9,7 +9,7 @@ import mill.api.Task
 import mill.api.TaskCtx
 import mill.api.DefaultTaskModule
 import mill.javalib.bsp.BspModule
-import mill.util.Jvm
+import mill.util.{Jvm, Version}
 import mill.api.JsonFormatters.given
 import mill.constants.EnvVars
 import mill.javalib.testrunner.{
@@ -358,24 +358,53 @@ object TestModule {
    * You can override the [[junitPlatformVersion]] and [[jupiterVersion]] task
    * or provide the JUnit 5-dependencies yourself.
    *
+   * In case the [[jupiterVersion]] is set (and it is > 5.12), it pulls in JUnit-BOM in [[bomMvnDeps]]. If this is
+   * true, then there is no need to specify the [[junitPlatformVersion]] anymore, because this is managed by the
+   * BOM.
+   *
    * See: https://junit.org/junit5/
    */
   trait Junit5 extends TestModule {
 
-    /** The JUnit 5 Platfrom version to use, or empty, if you want to provide the dependencies yourself. */
+    /** The JUnit 5 Platform version to use, or empty, if you want to provide the dependencies yourself. */
     def junitPlatformVersion: T[String] = Task { "" }
 
-    /** The JUnit Jupiter version to use, or empty, if you want to provide the dependencie yourself. */
+    /** The JUnit Jupiter version to use, or empty, if you want to provide the dependencies yourself. */
     def jupiterVersion: T[String] = Task { "" }
 
+    private def isJupiterBomAvailable: T[Boolean] = Task {
+      if (jupiterVersion().isBlank) {
+        false
+      } else {
+        Version.isAtLeast(jupiterVersion(), "5.12.0")(using Version.IgnoreQualifierOrdering)
+      }
+    }
+
     override def testFramework: T[String] = "com.github.sbt.junit.jupiter.api.JupiterFramework"
 
+    override def bomMvnDeps: T[Seq[Dep]] = Task {
+      super.bomMvnDeps() ++
+        Seq(jupiterVersion())
+          .filter(!_.isBlank() && isJupiterBomAvailable())
+          .flatMap(v =>
+            Seq(
+              mvn"org.junit:junit-bom:${v.trim()}"
+            )
+          )
+    }
+
     override def mandatoryMvnDeps: T[Seq[Dep]] = Task {
       super.mandatoryMvnDeps() ++
         Seq(mvn"${mill.javalib.api.Versions.jupiterInterface}") ++
-        Seq(junitPlatformVersion())
-          .filter(!_.isBlank())
-          .map(v => mvn"org.junit.platform:junit-platform-launcher:${v.trim()}") ++
+        Seq(junitPlatformVersion()).flatMap(v => {
+          if (!v.isBlank) {
+            Some(mvn"org.junit.platform:junit-platform-launcher:${v.trim()}")
+          } else if (isJupiterBomAvailable()) {
+            Some(mvn"org.junit.platform:junit-platform-launcher")
+          } else {
+            None
+          }
+        }) ++
         Seq(jupiterVersion())
           .filter(!_.isBlank())
           .map(v => mvn"org.junit.jupiter:junit-jupiter-api:${v.trim()}")
@@ -603,6 +632,9 @@ object TestModule {
   /**
    * TestModule that uses Spock Test Framework to run tests.
    * You can override the [[spockVersion]] task or provide the Spock dependency yourself.
+   *
+   * In case the version is set, it pulls in Spock-BOM in [[bomMvnDeps]] (only for 2.3 onwards) 
+   * and Spock-Core in [[mvnDeps]]
    */
   trait Spock extends TestModule.Junit5 {
 
@@ -611,12 +643,24 @@ object TestModule {
       ""
     }
 
-    /** The Groovy version to use, or the empty string, if you want to provide the Groovy test dependency yourself. */
-    def groovyVersion: T[String] = Task {
-      ""
+    private def isSpockBomAvailable: T[Boolean] = Task {
+      if (spockVersion().isBlank) {
+        false
+      } else {
+        Version.isAtLeast(spockVersion(), "2.3")(using Version.IgnoreQualifierOrdering)
+      }
     }
 
-    // TODO currently bomMvnDeps not in JavaModuleBase so we cannot pull in the Spock-BOM
+    override def bomMvnDeps: T[Seq[Dep]] = Task {
+      super.bomMvnDeps() ++
+        Seq(spockVersion())
+          .filter(!_.isBlank() && isSpockBomAvailable())
+          .flatMap(v =>
+            Seq(
+              mvn"org.spockframework:spock-bom:${v.trim()}"
+            )
+          )
+    }
 
     override def mandatoryMvnDeps: T[Seq[Dep]] = Task {
       super.mandatoryMvnDeps() ++
@@ -650,6 +694,7 @@ object TestModule {
     def mvnDeps: T[Seq[Dep]] = Seq()
     def mandatoryMvnDeps: T[Seq[Dep]] = Seq()
     def resources: T[Seq[PathRef]] = Task { Seq.empty[PathRef] }
+    def bomMvnDeps: T[Seq[Dep]] = Seq()
   }
 
   trait ScalaModuleBase extends mill.Module {
diff --git a/libs/javalib/test/src/mill/javalib/junit5/JUnit5Tests.scala b/libs/javalib/test/src/mill/javalib/junit5/JUnit5Tests.scala
index 227b5c4aaf09..35d28e33bed0 100644
--- a/libs/javalib/test/src/mill/javalib/junit5/JUnit5Tests.scala
+++ b/libs/javalib/test/src/mill/javalib/junit5/JUnit5Tests.scala
@@ -1,17 +1,34 @@
 package mill.javalib.junit5
 
-import mill.api.Discover
+import mill.api.Task.Simple
+import mill.api.{Discover, Module, Task}
 import mill.javalib.JavaModule
 import mill.javalib.TestModule
+import mill.javalib.DepSyntax
 import mill.testkit.{TestRootModule, UnitTester}
 import utest.*
 import mill.util.TokenReaders._
 
 object JUnit5Tests extends TestSuite {
 
+  val junitVersion = "5.13.4"
+
   object module extends TestRootModule with JavaModule {
     object test extends JavaTests with TestModule.Junit5
     lazy val millDiscover = Discover[this.type]
+
+    object deps extends Module {
+
+      object junitBom extends JavaTests with TestModule.Junit5 {
+        override def jupiterVersion: Simple[String] = junitVersion
+      }
+
+      object junitNoBom extends JavaTests with TestModule.Junit5 {
+        // JUnit-BOM available starting with 5.12.0
+        override def jupiterVersion: Simple[String] = "5.11.0"
+      }
+    }
+
   }
 
   val testModuleSourcesPath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "junit5"
@@ -32,5 +49,48 @@ object JUnit5Tests extends TestSuite {
         assert(qualifiedNames.forall(_.fullyQualifiedName == "qux.QuxTests"))
       }
     }
+    test("dependency management") {
+      def testEval() = UnitTester(module, testModuleSourcesPath)
+      val junitBom = mvn"org.junit:junit-bom:$junitVersion"
+      val jupiter = mvn"org.junit.jupiter:junit-jupiter-api:$junitVersion"
+      val junitPlatformLauncher = mvn"org.junit.platform:junit-platform-launcher"
+
+      test("jupiter added when version is set") {
+        testEval().scoped { eval =>
+          val Right(resultDeps) = eval.apply(module.deps.junitBom.mandatoryMvnDeps): @unchecked
+          assert(
+            resultDeps.value.contains(jupiter)
+          )
+        }
+      }
+
+      test("junit bom & platform are added when version is at least 5.12.0") {
+        testEval().scoped { eval =>
+          val Right(resultBom) = eval.apply(module.deps.junitBom.bomMvnDeps): @unchecked
+          assert(
+            resultBom.value.contains(junitBom)
+          )
+
+          val Right(resultDeps) = eval.apply(module.deps.junitBom.mandatoryMvnDeps): @unchecked
+          assert(
+            resultDeps.value.contains(junitPlatformLauncher)
+          )
+        }
+      }
+
+      test("junit bom & platform are NOT added when version is below 5.11.0") {
+        testEval().scoped { eval =>
+          val Right(resultBom) = eval.apply(module.deps.junitNoBom.bomMvnDeps): @unchecked
+          assert(
+            !resultBom.value.contains(junitBom)
+          )
+
+          val Right(resultDeps) = eval.apply(module.deps.junitNoBom.mandatoryMvnDeps): @unchecked
+          assert(
+            !resultDeps.value.contains(junitPlatformLauncher)
+          )
+        }
+      }
+    }
   }
 }

From eb13bc65bcc2e355b8974ce70969b4abf15639d5 Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Tue, 23 Sep 2025 12:34:02 +0200
Subject: [PATCH 06/23] test with cross-compile Groovy 4 & 5

---
 .../joint-compile/src/GroovyGreeter.groovy    |   0
 .../joint-compile/src/JavaMain.java           |   0
 .../joint-compile/src/JavaPrinter.java        |   0
 .../hello-groovy/spock/src/Hello.groovy       |  16 ++
 .../tests}/src/SpockTest.groovy               |   0
 .../src/mill/groovylib/HelloGroovyTests.scala | 138 ++++++++++--------
 6 files changed, 97 insertions(+), 57 deletions(-)
 rename libs/groovylib/test/resources/hello-groovy/{ => main}/joint-compile/src/GroovyGreeter.groovy (100%)
 rename libs/groovylib/test/resources/hello-groovy/{ => main}/joint-compile/src/JavaMain.java (100%)
 rename libs/groovylib/test/resources/hello-groovy/{ => main}/joint-compile/src/JavaPrinter.java (100%)
 create mode 100644 libs/groovylib/test/resources/hello-groovy/spock/src/Hello.groovy
 rename libs/groovylib/test/resources/hello-groovy/{main/spock => spock/tests}/src/SpockTest.groovy (100%)

diff --git a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy b/libs/groovylib/test/resources/hello-groovy/main/joint-compile/src/GroovyGreeter.groovy
similarity index 100%
rename from libs/groovylib/test/resources/hello-groovy/joint-compile/src/GroovyGreeter.groovy
rename to libs/groovylib/test/resources/hello-groovy/main/joint-compile/src/GroovyGreeter.groovy
diff --git a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java b/libs/groovylib/test/resources/hello-groovy/main/joint-compile/src/JavaMain.java
similarity index 100%
rename from libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaMain.java
rename to libs/groovylib/test/resources/hello-groovy/main/joint-compile/src/JavaMain.java
diff --git a/libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaPrinter.java b/libs/groovylib/test/resources/hello-groovy/main/joint-compile/src/JavaPrinter.java
similarity index 100%
rename from libs/groovylib/test/resources/hello-groovy/joint-compile/src/JavaPrinter.java
rename to libs/groovylib/test/resources/hello-groovy/main/joint-compile/src/JavaPrinter.java
diff --git a/libs/groovylib/test/resources/hello-groovy/spock/src/Hello.groovy b/libs/groovylib/test/resources/hello-groovy/spock/src/Hello.groovy
new file mode 100644
index 000000000000..c6d16c431c32
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/spock/src/Hello.groovy
@@ -0,0 +1,16 @@
+package hello
+
+class Hello {
+
+    static String getHelloString() {
+        return "Hello, world!"
+    }
+
+    static String sayHello(String name){
+        return "Hello, $name"
+    }
+
+    static void main(String[] args) {
+        println(getHelloString())
+    }
+}
\ No newline at end of file
diff --git a/libs/groovylib/test/resources/hello-groovy/main/spock/src/SpockTest.groovy b/libs/groovylib/test/resources/hello-groovy/spock/tests/src/SpockTest.groovy
similarity index 100%
rename from libs/groovylib/test/resources/hello-groovy/main/spock/src/SpockTest.groovy
rename to libs/groovylib/test/resources/hello-groovy/spock/tests/src/SpockTest.groovy
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index 8a0e1be24db4..8421fdf56cf7 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -10,11 +10,17 @@ import utest.*
 object HelloGroovyTests extends TestSuite {
 
   val groovy4Version = "4.0.28"
+  val groovy5Version = "5.0.1"
+  val groovyVersions = Seq(groovy4Version, groovy5Version)
   val junit5Version = sys.props.getOrElse("TEST_JUNIT5_VERSION", "5.13.4")
   val spockGroovy4Version = "2.3-groovy-4.0"
 
   object HelloGroovy extends TestRootModule {
 
+    trait GroovyVersionCross extends GroovyModule with Cross.Module[String]{
+      override def groovyVersion: Task.Simple[String] = crossValue
+    }
+    
     lazy val millDiscover = Discover[this.type]
 
     // needed for a special test where only the tests are written in Groovy while appcode remains Java
@@ -32,11 +38,22 @@ object HelloGroovyTests extends TestSuite {
 
     }
 
-    object `joint-compile` extends GroovyModule {
+    /**
+     * Currently Spock does not support Groovy 5, so that's why it's currently
+     * pulled out of the cross compilation.
+     */
+    object spock extends GroovyModule {
       override def groovyVersion: T[String] = groovy4Version
-      override def mainClass = Some("jointcompile.JavaMain")
+      
+      object tests extends GroovyTests with TestModule.Spock {
+        override def jupiterVersion: T[String] = junit5Version
+        override def spockVersion: T[String] = spockGroovy4Version
+      }
     }
 
+    /**
+     * Test to verify BOM-resolution only done starting with the minimal version
+     */
     object deps extends Module {
 
       object groovyBom extends GroovyModule {
@@ -61,34 +78,31 @@ object HelloGroovyTests extends TestSuite {
 
     }
 
-    trait Test extends GroovyModule {
+    trait Test extends GroovyVersionCross {
 
       override def mainClass = Some("hello.Hello")
 
-      object test extends GroovyTests with TestModule.Junit5 {
-        override def jupiterVersion: T[String] = junit5Version
-        override def junitPlatformVersion = "1.13.4"
-      }
-
       object script extends GroovyModule {
-        override def groovyVersion: T[String] = groovy4Version
+        override def groovyVersion: T[String] = crossValue
         override def mainClass = Some("HelloScript")
       }
 
       object staticcompile extends GroovyModule {
-        override def groovyVersion: T[String] = groovy4Version
+        override def groovyVersion: T[String] = crossValue
         override def mainClass = Some("hellostatic.HelloStatic")
       }
 
-      object spock extends GroovyTests with TestModule.Spock {
+      object `joint-compile` extends GroovyModule {
+        override def groovyVersion: T[String] = crossValue
+        override def mainClass = Some("jointcompile.JavaMain")
+      }
+
+      object test extends GroovyTests with TestModule.Junit5 {
         override def jupiterVersion: T[String] = junit5Version
-        override def spockVersion: T[String] = spockGroovy4Version
-        override def groovyVersion: T[String] = groovy4Version
+        override def junitPlatformVersion = "1.13.4"
       }
     }
-    object main extends Test {
-      override def groovyVersion: T[String] = groovy4Version
-    }
+    object main extends Cross[Test](groovyVersions) 
   }
 
   val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-groovy"
@@ -100,58 +114,84 @@ object HelloGroovyTests extends TestSuite {
 
   def tests: Tests = Tests {
 
-    def m = HelloGroovy.main
+    def main = HelloGroovy.main
+    def spock = HelloGroovy.spock
     def mixed = HelloGroovy.`groovy-tests`
-    def joint = HelloGroovy.`joint-compile`
     def deps = HelloGroovy.deps
 
     test("running a Groovy script") {
       testEval().scoped { eval =>
-        val Right(_) = eval.apply(m.script.run()): @unchecked
+        main.crossModules.foreach(m => {
+          val Right(_) = eval.apply(m.script.run()): @unchecked  
+        })
       }
     }
 
     test("running a Groovy script") {
       testEval().scoped { eval =>
-        val Right(_) = eval.apply(m.script.run()): @unchecked
+        main.crossModules.foreach(m => {
+          val Right(_) = eval.apply(m.script.run()): @unchecked
+        })
       }
     }
 
     test("compile & run Groovy module") {
       testEval().scoped { eval =>
-        val Right(result) = eval.apply(m.compile): @unchecked
+        main.crossModules.foreach(m => {
+          val Right(result) = eval.apply(m.compile): @unchecked
 
-        assert(
-          os.walk(result.value.classes.path).exists(_.last == "Hello.class")
-        )
+          assert(
+            os.walk(result.value.classes.path).exists(_.last == "Hello.class")
+          )
 
-        val Right(_) = eval.apply(m.run()): @unchecked
+          val Right(_) = eval.apply(m.run()): @unchecked
+        })
       }
     }
 
     test("compile & run Groovy JUnit5 test") {
       testEval().scoped { eval =>
+        main.crossModules.foreach(m => {
+          val Right(result) = eval.apply(m.test.compile): @unchecked
 
-        val Right(result) = eval.apply(m.test.compile): @unchecked
+          assert(
+            os.walk(result.value.classes.path).exists(_.last == "HelloTest.class")
+          )
 
-        assert(
-          os.walk(result.value.classes.path).exists(_.last == "HelloTest.class")
-        )
-
-        val Right(discovered) = eval.apply(m.test.discoveredTestClasses): @unchecked
-        assert(discovered.value == Seq("hello.tests.HelloTest"))
+          val Right(discovered) = eval.apply(m.test.discoveredTestClasses): @unchecked
+          assert(discovered.value == Seq("hello.tests.HelloTest"))
 
-        val Right(_) = eval.apply(m.test.testForked()): @unchecked
+          val Right(_) = eval.apply(m.test.testForked()): @unchecked
+        })
       }
     }
 
     test("compile & run a statically compiled Groovy") {
       testEval().scoped { eval =>
-        val Right(result) = eval.apply(m.staticcompile.compile): @unchecked
-        assert(
-          os.walk(result.value.classes.path).exists(_.last == "HelloStatic.class")
-        )
-        val Right(_) = eval.apply(m.staticcompile.run()): @unchecked
+        main.crossModules.foreach(m => {
+          val Right(result) = eval.apply(m.staticcompile.compile): @unchecked
+          assert(
+            os.walk(result.value.classes.path).exists(_.last == "HelloStatic.class")
+          )
+          val Right(_) = eval.apply(m.staticcompile.run()): @unchecked
+        })
+      }
+    }
+
+    test("compile joint (groovy <-> java cycle) & run") {
+      testEval().scoped { eval =>
+        main.crossModules.foreach(m => {
+          val Right(result) = eval.apply(m.`joint-compile`.compile): @unchecked
+
+          assert(
+            os.walk(result.value.classes.path).exists(_.last == "JavaPrinter.class")
+          )
+          assert(
+            os.walk(result.value.classes.path).exists(_.last == "GroovyGreeter.class")
+          )
+
+          val Right(_) = eval.apply(m.`joint-compile`.run()): @unchecked
+        })
       }
     }
 
@@ -168,31 +208,15 @@ object HelloGroovyTests extends TestSuite {
 
     test("compile & run Spock test") {
       testEval().scoped { eval =>
-
-        val Right(result1) = eval.apply(m.spock.compile): @unchecked
+        val Right(result1) = eval.apply(spock.tests.compile): @unchecked
         assert(
           os.walk(result1.value.classes.path).exists(_.last == "SpockTest.class")
         )
 
-        val Right(discovered) = eval.apply(m.spock.discoveredTestClasses): @unchecked
+        val Right(discovered) = eval.apply(spock.tests.discoveredTestClasses): @unchecked
         assert(discovered.value == Seq("hello.spock.SpockTest"))
 
-        val Right(_) = eval.apply(m.spock.testForked()): @unchecked
-      }
-    }
-
-    test("compile joint (groovy <-> java cycle) & run") {
-      testEval().scoped { eval =>
-        val Right(result) = eval.apply(joint.compile): @unchecked
-
-        assert(
-          os.walk(result.value.classes.path).exists(_.last == "JavaPrinter.class")
-        )
-        assert(
-          os.walk(result.value.classes.path).exists(_.last == "GroovyGreeter.class")
-        )
-
-        val Right(_) = eval.apply(joint.run()): @unchecked
+        val Right(_) = eval.apply(spock.tests.testForked()): @unchecked
       }
     }
 

From 13c7ec9be8a4a3d35cca55e97b5effd7d3373636 Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Tue, 23 Sep 2025 15:43:35 +0200
Subject: [PATCH 07/23] samples

---
 example/groovylib/basic/1-simple/build.mill   | 124 ++++++++++++++++++
 .../basic/1-simple/foo/src/foo/Foo.groovy     |  32 +++++
 .../1-simple/foo/test/src/foo/FooTest.groovy  |  15 +++
 .../basic/2-compat-modules/build.mill         |  59 +++++++++
 .../groovy/foo/FooIntegrationTests.groovy     |  12 ++
 .../foo/src/main/groovy/foo/Foo.groovy        |   9 ++
 .../foo/src/main/java/foo/Foo2.java           |   5 +
 .../foo/src/test/groovy/foo/FooTests.groovy   |  13 ++
 .../1-test-suite/bar/src/bar/Bar.groovy       |   9 ++
 .../bar/test/src/bar/BarTests.groovy          |  29 ++++
 .../groovylib/testing/1-test-suite/build.mill |  32 +++++
 .../1-test-suite/foo/src/foo/Foo.groovy       |  11 ++
 .../foo/test/src/foo/FooTests.groovy          |  29 ++++
 .../testing/2-integration-suite/build.mill    |  20 +++
 .../src/qux/QuxIntegrationTests.groovy        |  18 +++
 .../qux/src/qux/Qux.groovy                    |  11 ++
 .../qux/test/src/qux/QuxTests.groovy          |  18 +++
 example/groovylib/testing/3-spock/build.mill  |  15 +++
 .../testing/3-spock/src/foo/Calculator.groovy |   8 ++
 .../3-spock/test/foo/CalculatorSpec.groovy    |  17 +++
 .../testing/4-spock-for-java/build.mill       |  23 ++++
 .../src/main/java/foo/Calculator.java         |   8 ++
 .../src/test/groovy/foo/CalculatorSpec.groovy |  12 ++
 23 files changed, 529 insertions(+)
 create mode 100644 example/groovylib/basic/1-simple/build.mill
 create mode 100644 example/groovylib/basic/1-simple/foo/src/foo/Foo.groovy
 create mode 100644 example/groovylib/basic/1-simple/foo/test/src/foo/FooTest.groovy
 create mode 100644 example/groovylib/basic/2-compat-modules/build.mill
 create mode 100644 example/groovylib/basic/2-compat-modules/foo/src/integration/groovy/foo/FooIntegrationTests.groovy
 create mode 100644 example/groovylib/basic/2-compat-modules/foo/src/main/groovy/foo/Foo.groovy
 create mode 100644 example/groovylib/basic/2-compat-modules/foo/src/main/java/foo/Foo2.java
 create mode 100644 example/groovylib/basic/2-compat-modules/foo/src/test/groovy/foo/FooTests.groovy
 create mode 100644 example/groovylib/testing/1-test-suite/bar/src/bar/Bar.groovy
 create mode 100644 example/groovylib/testing/1-test-suite/bar/test/src/bar/BarTests.groovy
 create mode 100644 example/groovylib/testing/1-test-suite/build.mill
 create mode 100644 example/groovylib/testing/1-test-suite/foo/src/foo/Foo.groovy
 create mode 100644 example/groovylib/testing/1-test-suite/foo/test/src/foo/FooTests.groovy
 create mode 100644 example/groovylib/testing/2-integration-suite/build.mill
 create mode 100644 example/groovylib/testing/2-integration-suite/qux/integration/src/qux/QuxIntegrationTests.groovy
 create mode 100644 example/groovylib/testing/2-integration-suite/qux/src/qux/Qux.groovy
 create mode 100644 example/groovylib/testing/2-integration-suite/qux/test/src/qux/QuxTests.groovy
 create mode 100644 example/groovylib/testing/3-spock/build.mill
 create mode 100644 example/groovylib/testing/3-spock/src/foo/Calculator.groovy
 create mode 100644 example/groovylib/testing/3-spock/test/foo/CalculatorSpec.groovy
 create mode 100644 example/groovylib/testing/4-spock-for-java/build.mill
 create mode 100644 example/groovylib/testing/4-spock-for-java/src/main/java/foo/Calculator.java
 create mode 100644 example/groovylib/testing/4-spock-for-java/src/test/groovy/foo/CalculatorSpec.groovy

diff --git a/example/groovylib/basic/1-simple/build.mill b/example/groovylib/basic/1-simple/build.mill
new file mode 100644
index 000000000000..fc9fc75f966b
--- /dev/null
+++ b/example/groovylib/basic/1-simple/build.mill
@@ -0,0 +1,124 @@
+//// SNIPPET:BUILD
+
+package build
+import mill.*, groovylib.*
+
+object foo extends GroovyModule {
+  def groovyVersion = "5.0.1"
+
+  def mvnDeps = Seq(
+    mvn"org.apache.groovy:groovy-cli-commons", // BOM already loaded by module
+    mvn"org.apache.groovy:groovy-xml" // BOM already loaded by module
+  )
+  
+  def mainClass = Some("foo.Foo")
+
+  object test extends GroovyTests with TestModule.Junit5 {
+    def jupiterVersion = "5.13.4"
+
+    def mvnDeps = Seq(
+      mvn"org.apache.groovy:groovy-test" // BOM already loaded by module
+    )
+  }
+}
+
+// This is a basic Mill build for a single `GroovyModule`, with one
+// third-party dependency and a test suite using the JUnit framework.
+//// SNIPPET:TREE
+// ----
+// build.mill
+// foo/
+//     src/
+//         foo/Foo.groovy
+//     resources/
+//         ...
+//     test/
+//         src/
+//             foo/FooTest.groovy
+// out/foo/
+//     compile.json
+//     compile.dest/
+//     ...
+//     test/
+//         compile.json
+//         compile.dest/
+//         ...
+// ----
+//
+// NOTE: The default Mill source folder layout `foo/src/` differs from that of Maven/Gradle's
+// `foo/src/main/groovy`. If you wish to use the Maven source folder layout, e.g. for migrating
+// an existing codebase, you should use
+// xref:#_maven_compatible_modules[Maven-Compatible Modules]
+//
+//// SNIPPET:DEPENDENCIES
+//
+// This example project uses two third-party dependencies 
+// - Groovy-Cli-Commons for CLI argument parsing
+// - Groovy-Xml for HTML templating and escaping
+// and uses them to wrap a given input string in HTML templates with proper escaping.
+//
+// Typical usage of a `GroovyModule` is shown below
+
+/** Usage
+
+> ./mill resolve foo._ # List what tasks are available to run
+foo.assembly
+...
+foo.compile
+...
+foo.run
+...
+*/
+/** Usage
+> ./mill inspect foo.compile # Show documentation and inputs of a task
+foo.compile(GroovyModule...)
+    Compiles all the sources to JVM class files.
+    Compiles the current module to generate compiled classfiles/bytecode.
+Inputs:
+    foo.allJavaSourceFiles
+    foo.allGroovySourceFiles
+    foo.compileClasspath
+    foo.upstreamCompileOutput
+    foo.javacOptions
+    foo.zincReportCachedProblems
+...
+*/
+/** Usage
+> ./mill foo.compile # compile sources into classfiles
+...
+Compiling 1 Groovy sources to...
+*/
+/** Usage
+> ./mill foo.run # run the main method, if any
+error: Error: missing option --text
+...
+*/
+/** Usage
+> ./mill foo.run --text hello
+<h1>hello</h1>
+*/
+/** Usage
+> ./mill foo.test
+...
+Test foo.FooTest testSimple finished, ...
+Test foo.FooTest testEscaping finished, ...
+Test foo.FooTest finished, ...
+Test run finished: 0 failed, 0 ignored, 2 total, ...
+*/
+/** Usage
+> ./mill foo.assembly # bundle classfiles and libraries into a jar for deployment
+
+> ./mill show foo.assembly # show the output of the assembly task
+".../out/foo/assembly.dest/out.jar"
+
+> java -jar ./out/foo/assembly.dest/out.jar --text hello
+<h1>hello</h1>
+
+> ./out/foo/assembly.dest/out.jar --text hello # mac/linux
+<h1>hello</h1>
+
+> cp ./out/foo/assembly.dest/out.jar out.bat # windows
+
+> ./out.bat --text hello # windows
+<h1>hello</h1>
+*/
diff --git a/example/groovylib/basic/1-simple/foo/src/foo/Foo.groovy b/example/groovylib/basic/1-simple/foo/src/foo/Foo.groovy
new file mode 100644
index 000000000000..10e0cc77b475
--- /dev/null
+++ b/example/groovylib/basic/1-simple/foo/src/foo/Foo.groovy
@@ -0,0 +1,32 @@
+package foo
+
+import groovy.xml.MarkupBuilder
+import groovy.cli.commons.CliBuilder
+
+class Foo {
+    static String generateHtml(String text) {
+        def writer = new StringWriter()
+        new MarkupBuilder(writer).h1 {
+            mkp.yield text
+        }
+        writer.toString()
+    }
+
+    static void main(String[] args) {
+        def cli = new CliBuilder(usage:'help')
+        cli.t(longOpt:'text', args: 1, 'Passes text to the HTML generation')
+        def options = cli.parse(args)
+
+        if (!options) {
+            return
+        }
+
+        if (options.h) {
+            cli.usage()
+            return
+        }
+
+        String textToProcess = options.t ?: "hello from main"
+        println generateHtml(textToProcess)
+    }
+}
diff --git a/example/groovylib/basic/1-simple/foo/test/src/foo/FooTest.groovy b/example/groovylib/basic/1-simple/foo/test/src/foo/FooTest.groovy
new file mode 100644
index 000000000000..6e8f048873c7
--- /dev/null
+++ b/example/groovylib/basic/1-simple/foo/test/src/foo/FooTest.groovy
@@ -0,0 +1,15 @@
+package foo
+
+import org.junit.jupiter.api.Test
+
+class FooTest {
+    @Test
+    void "generate html created properly"() {
+        assert Foo.generateHtml("hello") == "<h1>hello</h1>"
+    }
+    
+    @Test
+    void "generated html is properly escaped"() {
+        assert Foo.generateHtml("<hello>") == "<h1>&lt;hello&gt;</h1>"
+    }
+}
diff --git a/example/groovylib/basic/2-compat-modules/build.mill b/example/groovylib/basic/2-compat-modules/build.mill
new file mode 100644
index 000000000000..1c1c0712a8c7
--- /dev/null
+++ b/example/groovylib/basic/2-compat-modules/build.mill
@@ -0,0 +1,59 @@
+//// SNIPPET:ALL
+// Mill's default folder layout of `foo/src/` and `foo/test/src` differs from that
+// of Maven or Gradle's `foo/src/main/groovy/` and `foo/src/test/groovy/`. If you are
+// migrating an existing codebase, you can use Mill's `GroovyMavenModule` and
+// `GroovyMavenTests` as shown below to preserve filesystem compatibility with an existing
+// Maven or Gradle build:
+
+package build
+import mill.*, groovylib.*
+
+object foo extends GroovyMavenModule {
+
+  def groovyVersion = "5.0.1"
+
+  object test extends GroovyMavenTests with TestModule.Junit5 {
+  }
+  object integration extends GroovyMavenTests with TestModule.Junit5 {
+  }
+}
+
+// `GroovyMavenModule` is a variant of `GroovyModule`
+// that uses the more verbose folder layout of Maven, `sbt`, and other tools:
+//
+// - `foo/src/main/java`
+// - `foo/src/main/groovy`
+// - `foo/src/test/java`
+// - `foo/src/test/groovy`
+// - `foo/src/integration/java`
+// - `foo/src/integration/groovy`
+//
+// Rather than Mill's
+//
+// - `foo/src`
+// - `foo/test/src`
+//
+// This is especially useful if you are migrating from Maven to Mill (or vice
+// versa), during which a particular module may be built using both Maven and
+// Mill at the same time
+
+/** Usage
+
+> ./mill foo.compile
+Compiling 1 Groovy source...
+
+> ./mill foo.test.compile
+Compiling 1 Groovy source...
+
+> ./mill foo.test.testForked
+...foo.FooTests hello ...
+
+> ./mill foo.test
+...foo.FooTests hello ...
+
+> ./mill foo.integration
+...foo.FooIntegrationTests hello ...
+
+*/
+
+// For more details on migrating from other build tools, see xref:migrating/migrating.adoc[]
diff --git a/example/groovylib/basic/2-compat-modules/foo/src/integration/groovy/foo/FooIntegrationTests.groovy b/example/groovylib/basic/2-compat-modules/foo/src/integration/groovy/foo/FooIntegrationTests.groovy
new file mode 100644
index 000000000000..a5c50328c1ff
--- /dev/null
+++ b/example/groovylib/basic/2-compat-modules/foo/src/integration/groovy/foo/FooIntegrationTests.groovy
@@ -0,0 +1,12 @@
+package foo
+
+import org.junit.jupiter.api.Test
+
+class FooIntegrationTests {
+    @Test
+    void "hello should print correct greeting"() {
+        // Groovy creates an implicit class for the script named after the file
+        def foo = new Foo()
+        assert foo.hello() == "Hello World, Earth"
+    }
+}
diff --git a/example/groovylib/basic/2-compat-modules/foo/src/main/groovy/foo/Foo.groovy b/example/groovylib/basic/2-compat-modules/foo/src/main/groovy/foo/Foo.groovy
new file mode 100644
index 000000000000..0054d20ec1b1
--- /dev/null
+++ b/example/groovylib/basic/2-compat-modules/foo/src/main/groovy/foo/Foo.groovy
@@ -0,0 +1,9 @@
+package foo
+
+def run(){
+    println(hello())
+}
+
+def hello() {
+    "Hello World, ${Foo2.VALUE}"
+}
diff --git a/example/groovylib/basic/2-compat-modules/foo/src/main/java/foo/Foo2.java b/example/groovylib/basic/2-compat-modules/foo/src/main/java/foo/Foo2.java
new file mode 100644
index 000000000000..47684927c22e
--- /dev/null
+++ b/example/groovylib/basic/2-compat-modules/foo/src/main/java/foo/Foo2.java
@@ -0,0 +1,5 @@
+package foo;
+
+public class Foo2 {
+  public static final String VALUE = "Earth";
+}
diff --git a/example/groovylib/basic/2-compat-modules/foo/src/test/groovy/foo/FooTests.groovy b/example/groovylib/basic/2-compat-modules/foo/src/test/groovy/foo/FooTests.groovy
new file mode 100644
index 000000000000..80ba076e8959
--- /dev/null
+++ b/example/groovylib/basic/2-compat-modules/foo/src/test/groovy/foo/FooTests.groovy
@@ -0,0 +1,13 @@
+package foo
+
+import org.junit.jupiter.api.Test
+
+class FooTest {
+
+    @Test
+    void "hello should print correct greeting"() {
+        // Groovy creates an implicit class for the script named after the file
+        def foo = new Foo()
+        assert foo.hello() == "Hello World, Earth"
+    }
+}
\ No newline at end of file
diff --git a/example/groovylib/testing/1-test-suite/bar/src/bar/Bar.groovy b/example/groovylib/testing/1-test-suite/bar/src/bar/Bar.groovy
new file mode 100644
index 000000000000..9ea74e14b77b
--- /dev/null
+++ b/example/groovylib/testing/1-test-suite/bar/src/bar/Bar.groovy
@@ -0,0 +1,9 @@
+package bar
+
+def hello() {
+    "Hello World"
+}
+
+def run(){
+    println new Bar().hello()
+}
diff --git a/example/groovylib/testing/1-test-suite/bar/test/src/bar/BarTests.groovy b/example/groovylib/testing/1-test-suite/bar/test/src/bar/BarTests.groovy
new file mode 100644
index 000000000000..3f9c8202d182
--- /dev/null
+++ b/example/groovylib/testing/1-test-suite/bar/test/src/bar/BarTests.groovy
@@ -0,0 +1,29 @@
+package bar
+
+import org.junit.jupiter.api.Test
+import groovy.mock.interceptor.MockFor
+
+class BarTests{
+    @Test
+    void "hello"() {
+        def result = new Bar().hello()
+        assert result == "Hello World"
+    }
+
+    @Test
+    void "world"() {
+        def result = new Bar().hello()
+        assert result.endsWith("World")
+    }
+
+    @Test
+    void "using groovy mocks"() {
+        def mockBar = new MockFor(Bar)
+        mockBar.demand.hello { "Hello GroovyMock World" }
+
+        mockBar.use{
+            def result = new Bar().hello()
+            assert result == "Hello GroovyMock World"
+        }
+    }
+}
diff --git a/example/groovylib/testing/1-test-suite/build.mill b/example/groovylib/testing/1-test-suite/build.mill
new file mode 100644
index 000000000000..6bcfb5588f54
--- /dev/null
+++ b/example/groovylib/testing/1-test-suite/build.mill
@@ -0,0 +1,32 @@
+//// SNIPPET:BUILD1
+package build
+import mill.*, groovylib.*
+
+object foo extends GroovyModule {
+
+  def groovyVersion = "5.0.1"
+
+  object test extends GroovyTests with TestModule.Junit5 {
+    def jupiterVersion = "5.13.4"
+
+    def mvnDeps = Seq(
+      mvn"org.apache.groovy:groovy-test" // BOM already loaded by module
+    )
+  }
+}
+
+object bar extends GroovyModule {
+
+  def mainClass = Some("bar.Bar")
+
+  def groovyVersion = "5.0.1"
+
+  object test extends GroovyTests, TestModule.Junit5 {
+    def jupiterVersion = "5.13.4"
+
+    def mvnDeps = Seq(
+      mvn"org.apache.groovy:groovy-test" // BOM already loaded by module
+    )
+  }
+}
+
diff --git a/example/groovylib/testing/1-test-suite/foo/src/foo/Foo.groovy b/example/groovylib/testing/1-test-suite/foo/src/foo/Foo.groovy
new file mode 100644
index 000000000000..3145fff350e6
--- /dev/null
+++ b/example/groovylib/testing/1-test-suite/foo/src/foo/Foo.groovy
@@ -0,0 +1,11 @@
+package foo
+
+class Foo {
+    def hello() {
+        "Hello World"
+    }
+
+    static void main(String[] args){
+        println Foo().hello()
+    }
+}
diff --git a/example/groovylib/testing/1-test-suite/foo/test/src/foo/FooTests.groovy b/example/groovylib/testing/1-test-suite/foo/test/src/foo/FooTests.groovy
new file mode 100644
index 000000000000..5390008ede06
--- /dev/null
+++ b/example/groovylib/testing/1-test-suite/foo/test/src/foo/FooTests.groovy
@@ -0,0 +1,29 @@
+package foo
+
+import org.junit.jupiter.api.Test
+import groovy.mock.interceptor.MockFor
+
+class FooMoreTests{
+    @Test
+    void "hello"() {
+        def result = new Foo().hello()
+        assert result == "Hello World"
+    }
+
+    @Test
+    void "world"() {
+        def result = new Foo().hello()
+        assert result.endsWith("World")
+    }
+
+    @Test
+    void "using groovy mocks"() {
+        def mockFoo = new MockFor(Foo)
+        mockFoo.demand.hello { "Hello GroovyMock World" }
+
+        mockFoo.use{
+            def result = new Foo().hello()
+            assert result == "Hello GroovyMock World"
+        }
+    }
+}
diff --git a/example/groovylib/testing/2-integration-suite/build.mill b/example/groovylib/testing/2-integration-suite/build.mill
new file mode 100644
index 000000000000..b8eae997aab1
--- /dev/null
+++ b/example/groovylib/testing/2-integration-suite/build.mill
@@ -0,0 +1,20 @@
+//// SNIPPET:BUILD2
+package build
+import mill.*, groovylib.*
+object qux extends GroovyModule {
+
+  def groovyVersion = "5.0.1"
+
+  object test extends GroovyTests with TestModule.Junit5 {
+    def mvnDeps = super.mvnDeps() ++ Seq(
+      mvn"org.apache.groovy:groovy-test"
+    )
+  }
+  object integration extends GroovyTests with TestModule.Junit5 {
+    def mvnDeps = super.mvnDeps() ++ Seq(
+      mvn"org.apache.groovy:groovy-test"
+    )
+  }
+}
+
+// The integration suite is just another regular test module within the parent GroovyModule
\ No newline at end of file
diff --git a/example/groovylib/testing/2-integration-suite/qux/integration/src/qux/QuxIntegrationTests.groovy b/example/groovylib/testing/2-integration-suite/qux/integration/src/qux/QuxIntegrationTests.groovy
new file mode 100644
index 000000000000..c04f366bd689
--- /dev/null
+++ b/example/groovylib/testing/2-integration-suite/qux/integration/src/qux/QuxIntegrationTests.groovy
@@ -0,0 +1,18 @@
+package qux
+
+import org.junit.jupiter.api.Test
+
+class QuxIntegrationTests {
+
+    @Test
+    void "hello"() {
+        def result = new Qux().hello()
+        assert result == "Hello World"
+    }
+
+    @Test
+    void "world"() {
+        def result = new Qux().hello()
+        assert result.endsWith("World")
+    }
+}
diff --git a/example/groovylib/testing/2-integration-suite/qux/src/qux/Qux.groovy b/example/groovylib/testing/2-integration-suite/qux/src/qux/Qux.groovy
new file mode 100644
index 000000000000..c04e966f9105
--- /dev/null
+++ b/example/groovylib/testing/2-integration-suite/qux/src/qux/Qux.groovy
@@ -0,0 +1,11 @@
+package qux
+
+class Qux {
+    static void main(String[] args){
+        println(hello())
+    }
+
+    String hello(){
+        "Hello World"
+    }
+}
diff --git a/example/groovylib/testing/2-integration-suite/qux/test/src/qux/QuxTests.groovy b/example/groovylib/testing/2-integration-suite/qux/test/src/qux/QuxTests.groovy
new file mode 100644
index 000000000000..b97ae1a45cde
--- /dev/null
+++ b/example/groovylib/testing/2-integration-suite/qux/test/src/qux/QuxTests.groovy
@@ -0,0 +1,18 @@
+package qux
+
+import org.junit.jupiter.api.Test
+
+class QuxTests {
+
+    @Test
+    void "hello"() {
+        def result = new Qux().hello()
+        assert result == "Hello World"
+    }
+
+    @Test
+    void "world"() {
+        def result = new Qux().hello()
+        assert result.endsWith("World")
+    }
+}
\ No newline at end of file
diff --git a/example/groovylib/testing/3-spock/build.mill b/example/groovylib/testing/3-spock/build.mill
new file mode 100644
index 000000000000..ba8a4b5f2af0
--- /dev/null
+++ b/example/groovylib/testing/3-spock/build.mill
@@ -0,0 +1,15 @@
+//// SNIPPET:BUILD4
+package build
+import mill.*, groovylib.*
+
+object `package` extends GroovyModule {
+
+  def groovyVersion = "4.0.28"
+
+  object test extends GroovyTests with TestModule.Spock {
+    def spockVersion = "2.3-groovy-4.0"
+    def jupiterVersion = "5.13.4"
+  }
+}
+
+
diff --git a/example/groovylib/testing/3-spock/src/foo/Calculator.groovy b/example/groovylib/testing/3-spock/src/foo/Calculator.groovy
new file mode 100644
index 000000000000..015c700376b9
--- /dev/null
+++ b/example/groovylib/testing/3-spock/src/foo/Calculator.groovy
@@ -0,0 +1,8 @@
+package foo
+
+class Calculator {
+
+  int add(int a, int b) {
+    return a + b
+  }
+}
diff --git a/example/groovylib/testing/3-spock/test/foo/CalculatorSpec.groovy b/example/groovylib/testing/3-spock/test/foo/CalculatorSpec.groovy
new file mode 100644
index 000000000000..35f4535ab7f6
--- /dev/null
+++ b/example/groovylib/testing/3-spock/test/foo/CalculatorSpec.groovy
@@ -0,0 +1,17 @@
+package foo
+
+def "Calculator add: #a + #b = #expected"(){
+    given:
+    def sut = new Calculator()
+
+    when:
+    def result = sut.add(a, b)
+
+    then:
+    result == expected
+
+    where:
+    a  | b  | expected
+    2  | 2  |  4
+    -2 | -2 | -4
+}
\ No newline at end of file
diff --git a/example/groovylib/testing/4-spock-for-java/build.mill b/example/groovylib/testing/4-spock-for-java/build.mill
new file mode 100644
index 000000000000..38a628b4d648
--- /dev/null
+++ b/example/groovylib/testing/4-spock-for-java/build.mill
@@ -0,0 +1,23 @@
+//// SNIPPET:BUILD5
+package build
+import mill.*, groovylib.*
+
+object `package` extends JavaMavenModuleWithGroovyTests {
+
+  object test extends GroovyMavenTests with TestModule.Spock {
+    def spockVersion = "2.3-groovy-4.0"
+    def groovyVersion = "4.0.28"
+    def jupiterVersion = "5.13.4"
+  }
+}
+
+// `JavaMavenModuleWithGroovyTests` is a variant of `JavaModule` which also
+// includes `MavenModule` and has a special `test` trait for Groovy tests:
+//
+// - `foo/src/main/java`
+// - `foo/src/test/groovy`
+//
+// This is usefull for Java projects which use Groovy only for testing.
+// For non Maven-layout projects, this convenience trait is not necessary
+// because you can just use `GroovyModule` for your test object instead.
+
diff --git a/example/groovylib/testing/4-spock-for-java/src/main/java/foo/Calculator.java b/example/groovylib/testing/4-spock-for-java/src/main/java/foo/Calculator.java
new file mode 100644
index 000000000000..bee08ac9ad6e
--- /dev/null
+++ b/example/groovylib/testing/4-spock-for-java/src/main/java/foo/Calculator.java
@@ -0,0 +1,8 @@
+package foo;
+
+public class Calculator {
+
+  public static int add(int a, int b) {
+    return a + b;
+  }
+}
diff --git a/example/groovylib/testing/4-spock-for-java/src/test/groovy/foo/CalculatorSpec.groovy b/example/groovylib/testing/4-spock-for-java/src/test/groovy/foo/CalculatorSpec.groovy
new file mode 100644
index 000000000000..465b2bb4cd5e
--- /dev/null
+++ b/example/groovylib/testing/4-spock-for-java/src/test/groovy/foo/CalculatorSpec.groovy
@@ -0,0 +1,12 @@
+package foo
+
+def "Calculator add: #a + #b = #result"(){
+    expect:
+    Calculator.add(a, b) == result
+
+    where:
+    a  | b
+    2  | 2
+    -2 | -2
+    result = a + b
+}
\ No newline at end of file

From ea34a49d2dd52c9aa901eed8e101d9ad0c2b46cf Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Wed, 24 Sep 2025 11:42:01 +0200
Subject: [PATCH 08/23] docs

---
 .../modules/ROOT/pages/groovylib/intro.adoc   | 19 +++++++++++++
 .../modules/ROOT/pages/groovylib/testing.adoc | 28 +++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 website/docs/modules/ROOT/pages/groovylib/intro.adoc
 create mode 100644 website/docs/modules/ROOT/pages/groovylib/testing.adoc

diff --git a/website/docs/modules/ROOT/pages/groovylib/intro.adoc b/website/docs/modules/ROOT/pages/groovylib/intro.adoc
new file mode 100644
index 000000000000..0538fa008d79
--- /dev/null
+++ b/website/docs/modules/ROOT/pages/groovylib/intro.adoc
@@ -0,0 +1,19 @@
+
+= Building Groovy with Mill
+:page-aliases: Groovy_Intro_to_Mill.adoc
+:language: Groovy
+:language-small: groovy
+
+include::partial$Intro_Header.adoc[]
+
+NOTE: Mill Groovy support is currently still under active development.
+It is expected to continue evolving over time.
+
+== Simple Groovy Module
+
+include::partial$example/groovylib/basic/1-simple.adoc[]
+
+== Maven-Compatible Modules
+
+include::partial$example/groovylib/basic/2-compat-modules.adoc[]
+
diff --git a/website/docs/modules/ROOT/pages/groovylib/testing.adoc b/website/docs/modules/ROOT/pages/groovylib/testing.adoc
new file mode 100644
index 000000000000..47296507879b
--- /dev/null
+++ b/website/docs/modules/ROOT/pages/groovylib/testing.adoc
@@ -0,0 +1,28 @@
+= Testing Groovy Projects
+:page-aliases: Testing_Groovy_Projects.adoc
+
+
+
+This page will discuss common topics around working with test suites using the Mill build tool
+
+== Defining Unit Test Suites
+
+include::partial$example/groovylib/testing/1-test-suite.adoc[]
+
+== Defining Integration Test Suites
+
+include::partial$example/groovylib/testing/2-integration-suite.adoc[]
+
+== Using Spock
+
+include::partial$example/groovylib/testing/3-spock.adoc[]
+
+== Using Spock in Java projects with Maven layout
+
+include::partial$example/groovylib/testing/4-java-spock.adoc[]
+
+== Github Actions Test Reports
+
+If you use Github Actions for CI, you can use https://github.com/mikepenz/action-junit-report in
+your pipeline to render the generated `test-report.xml` files nicely on Github. See
+https://github.com/com-lihaoyi/mill/pull/4218/files for an example integration
\ No newline at end of file

From 9a26ea33cee394b453898b0607de0bd68558c02e Mon Sep 17 00:00:00 2001
From: "autofix-ci[bot]" <114827586+autofix-ci[bot]@users.noreply.github.com>
Date: Wed, 24 Sep 2025 10:24:25 +0000
Subject: [PATCH 09/23] [autofix.ci] apply automated fixes

---
 example/groovylib/basic/1-simple/build.mill            |  4 ++--
 example/groovylib/basic/2-compat-modules/build.mill    |  6 ++----
 example/groovylib/testing/1-test-suite/build.mill      |  1 -
 .../groovylib/testing/2-integration-suite/build.mill   |  2 +-
 example/groovylib/testing/3-spock/build.mill           |  2 --
 example/groovylib/testing/4-spock-for-java/build.mill  |  1 -
 .../test/src/mill/groovylib/HelloGroovyTests.scala     | 10 +++++-----
 libs/javalib/src/mill/javalib/TestModule.scala         |  2 +-
 8 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/example/groovylib/basic/1-simple/build.mill b/example/groovylib/basic/1-simple/build.mill
index fc9fc75f966b..246277785c36 100644
--- a/example/groovylib/basic/1-simple/build.mill
+++ b/example/groovylib/basic/1-simple/build.mill
@@ -10,7 +10,7 @@ object foo extends GroovyModule {
     mvn"org.apache.groovy:groovy-cli-commons", // BOM already loaded by module
     mvn"org.apache.groovy:groovy-xml" // BOM already loaded by module
   )
-  
+
   def mainClass = Some("foo.Foo")
 
   object test extends GroovyTests with TestModule.Junit5 {
@@ -52,7 +52,7 @@ object foo extends GroovyModule {
 //
 //// SNIPPET:DEPENDENCIES
 //
-// This example project uses two third-party dependencies 
+// This example project uses two third-party dependencies
 // - Groovy-Cli-Commons for CLI argument parsing
 // - Groovy-Xml for HTML templating and escaping
 // and uses them to wrap a given input string in HTML templates with proper escaping.
diff --git a/example/groovylib/basic/2-compat-modules/build.mill b/example/groovylib/basic/2-compat-modules/build.mill
index 1c1c0712a8c7..144115e09071 100644
--- a/example/groovylib/basic/2-compat-modules/build.mill
+++ b/example/groovylib/basic/2-compat-modules/build.mill
@@ -12,10 +12,8 @@ object foo extends GroovyMavenModule {
 
   def groovyVersion = "5.0.1"
 
-  object test extends GroovyMavenTests with TestModule.Junit5 {
-  }
-  object integration extends GroovyMavenTests with TestModule.Junit5 {
-  }
+  object test extends GroovyMavenTests with TestModule.Junit5 {}
+  object integration extends GroovyMavenTests with TestModule.Junit5 {}
 }
 
 // `GroovyMavenModule` is a variant of `GroovyModule`
diff --git a/example/groovylib/testing/1-test-suite/build.mill b/example/groovylib/testing/1-test-suite/build.mill
index 6bcfb5588f54..652533e72b59 100644
--- a/example/groovylib/testing/1-test-suite/build.mill
+++ b/example/groovylib/testing/1-test-suite/build.mill
@@ -29,4 +29,3 @@ object bar extends GroovyModule {
     )
   }
 }
-
diff --git a/example/groovylib/testing/2-integration-suite/build.mill b/example/groovylib/testing/2-integration-suite/build.mill
index b8eae997aab1..04c4f0f0a3da 100644
--- a/example/groovylib/testing/2-integration-suite/build.mill
+++ b/example/groovylib/testing/2-integration-suite/build.mill
@@ -17,4 +17,4 @@ object qux extends GroovyModule {
   }
 }
 
-// The integration suite is just another regular test module within the parent GroovyModule
\ No newline at end of file
+// The integration suite is just another regular test module within the parent GroovyModule
diff --git a/example/groovylib/testing/3-spock/build.mill b/example/groovylib/testing/3-spock/build.mill
index ba8a4b5f2af0..331a776db914 100644
--- a/example/groovylib/testing/3-spock/build.mill
+++ b/example/groovylib/testing/3-spock/build.mill
@@ -11,5 +11,3 @@ object `package` extends GroovyModule {
     def jupiterVersion = "5.13.4"
   }
 }
-
-
diff --git a/example/groovylib/testing/4-spock-for-java/build.mill b/example/groovylib/testing/4-spock-for-java/build.mill
index 38a628b4d648..d6be164c3b44 100644
--- a/example/groovylib/testing/4-spock-for-java/build.mill
+++ b/example/groovylib/testing/4-spock-for-java/build.mill
@@ -20,4 +20,3 @@ object `package` extends JavaMavenModuleWithGroovyTests {
 // This is usefull for Java projects which use Groovy only for testing.
 // For non Maven-layout projects, this convenience trait is not necessary
 // because you can just use `GroovyModule` for your test object instead.
-
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index 8421fdf56cf7..740751799d52 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -17,10 +17,10 @@ object HelloGroovyTests extends TestSuite {
 
   object HelloGroovy extends TestRootModule {
 
-    trait GroovyVersionCross extends GroovyModule with Cross.Module[String]{
+    trait GroovyVersionCross extends GroovyModule with Cross.Module[String] {
       override def groovyVersion: Task.Simple[String] = crossValue
     }
-    
+
     lazy val millDiscover = Discover[this.type]
 
     // needed for a special test where only the tests are written in Groovy while appcode remains Java
@@ -44,7 +44,7 @@ object HelloGroovyTests extends TestSuite {
      */
     object spock extends GroovyModule {
       override def groovyVersion: T[String] = groovy4Version
-      
+
       object tests extends GroovyTests with TestModule.Spock {
         override def jupiterVersion: T[String] = junit5Version
         override def spockVersion: T[String] = spockGroovy4Version
@@ -102,7 +102,7 @@ object HelloGroovyTests extends TestSuite {
         override def junitPlatformVersion = "1.13.4"
       }
     }
-    object main extends Cross[Test](groovyVersions) 
+    object main extends Cross[Test](groovyVersions)
   }
 
   val resourcePath = os.Path(sys.env("MILL_TEST_RESOURCE_DIR")) / "hello-groovy"
@@ -122,7 +122,7 @@ object HelloGroovyTests extends TestSuite {
     test("running a Groovy script") {
       testEval().scoped { eval =>
         main.crossModules.foreach(m => {
-          val Right(_) = eval.apply(m.script.run()): @unchecked  
+          val Right(_) = eval.apply(m.script.run()): @unchecked
         })
       }
     }
diff --git a/libs/javalib/src/mill/javalib/TestModule.scala b/libs/javalib/src/mill/javalib/TestModule.scala
index 02d826dd0ade..f71196898b3b 100644
--- a/libs/javalib/src/mill/javalib/TestModule.scala
+++ b/libs/javalib/src/mill/javalib/TestModule.scala
@@ -633,7 +633,7 @@ object TestModule {
    * TestModule that uses Spock Test Framework to run tests.
    * You can override the [[spockVersion]] task or provide the Spock dependency yourself.
    *
-   * In case the version is set, it pulls in Spock-BOM in [[bomMvnDeps]] (only for 2.3 onwards) 
+   * In case the version is set, it pulls in Spock-BOM in [[bomMvnDeps]] (only for 2.3 onwards)
    * and Spock-Core in [[mvnDeps]]
    */
   trait Spock extends TestModule.Junit5 {

From b8d28f7f24d4426f8ba60bc7d6ad8ad2c14943bd Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Wed, 24 Sep 2025 14:47:00 +0200
Subject: [PATCH 10/23] Groovy Compiler options for bytecode version, preview
 features and ast transoformations

---
 .../api/GroovyCompilerConfiguration.scala     |  6 +++
 .../groovylib/worker/api/GroovyWorker.scala   | 13 +++--
 .../src/mill/groovylib/GroovyModule.scala     | 36 ++++++++++++--
 .../src/mill/groovylib/publish/exports.scala  |  2 +-
 .../worker/impl/GroovyWorkerImpl.scala        | 48 +++++++++++--------
 5 files changed, 76 insertions(+), 29 deletions(-)
 create mode 100644 libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala

diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala
new file mode 100644
index 000000000000..414bfbe6e13d
--- /dev/null
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala
@@ -0,0 +1,6 @@
+package mill.groovylib.worker.api
+
+case class GroovyCompilerConfiguration (
+  enablePreview: Boolean = false,
+  disabledGlobalAstTransformations: Set[String]= Set.empty,
+  targetBytecode: Option[String]= None)
diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
index d92e90463e7a..32a7493f44d2 100644
--- a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
@@ -1,7 +1,6 @@
 package mill.groovylib.worker.api
 
-import mill.api.TaskCtx
-import mill.api.Result
+import mill.api.{Result, TaskCtx}
 import mill.javalib.api.CompilationResult
 
 /**
@@ -20,7 +19,8 @@ trait GroovyWorker {
   def compileGroovyStubs(
       sourceFiles: Seq[os.Path],
       classpath: Seq[os.Path],
-      outputDir: os.Path
+      outputDir: os.Path,
+      config: GroovyCompilerConfiguration
   )(implicit
       ctx: TaskCtx
   )
@@ -30,7 +30,12 @@ trait GroovyWorker {
    * Compiles the Groovy sources. In a mixed setup this method assumes that the Java stubs
    * are already present in the outputDir.
    */
-  def compile(sourceFiles: Seq[os.Path], classpath: Seq[os.Path], outputDir: os.Path)(implicit
+  def compile(
+      sourceFiles: Seq[os.Path],
+      classpath: Seq[os.Path],
+      outputDir: os.Path,
+      config: GroovyCompilerConfiguration
+  )(implicit
       ctx: TaskCtx
   )
       : Result[CompilationResult]
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 284315fac4d2..555747846885 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -9,6 +9,7 @@ import mill.javalib.{Dep, JavaModule, JvmWorkerModule, Lib}
 import mill.*
 import mainargs.Flag
 import mill.api.daemon.internal.bsp.{BspBuildTarget, BspModuleApi}
+import mill.groovylib.worker.api.GroovyCompilerConfiguration
 import mill.javalib.api.internal.{JavaCompilerOptions, JvmWorkerApi, ZincCompileJava}
 import mill.util.Version
 
@@ -49,6 +50,29 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
     allGroovySourceFiles() ++ allJavaSourceFiles()
   }
 
+  /**
+   * Specifiy the bytecode version for the Groovy compiler.
+   * {{{
+   *   def targetBytecode = Some("17")
+   * }}}
+   */
+  def targetBytecode: T[Option[String]] = None
+
+  /**
+   * Specify if the Groovy compiler should enable preview features.
+   */
+  def enablePreview: T[Boolean] = false
+
+  /**
+   * Specify which global AST transformations should be disabled. Be aware that transformations
+   * like [[groovy.transform.Immutable]] are so-called "local" transformations and will not be
+   * affected.
+   *
+   * see [[https://docs.groovy-lang.org/latest/html/api/org/codehaus/groovy/control/CompilerConfiguration.html#setDisabledGlobalASTTransformations(java.util.Set) Groovy-Docs]]
+   */
+  def disabledGlobalAstTransformations: T[Set[String]] = Set.empty
+
+
   /**
    * All individual Java source files fed into the compiler.
    * Subset of [[allSourceFiles]].
@@ -92,7 +116,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
   }
 
   /**
-   * The Ivy/Coursier dependencies resembling the Groovy compiler.
+   * The Coursier dependencies resembling the Groovy compiler.
    *
    * Default is derived from [[groovyVersion]].
    */
@@ -128,6 +152,12 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
       val compileCp = compileClasspath().map(_.path).filter(os.exists)
       val updateCompileOutput = upstreamCompileOutput()
 
+      val config = GroovyCompilerConfiguration(
+        enablePreview = enablePreview(),
+        targetBytecode = targetBytecode(),
+        disabledGlobalAstTransformations = disabledGlobalAstTransformations(),
+      )
+
       def compileJava: Result[CompilationResult] = {
         ctx.log.info(
           s"Compiling ${javaSourceFiles.size} Java sources to $classes ..."
@@ -150,7 +180,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
 
         val workerStubResult =
           GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
-            _.compileGroovyStubs(groovySourceFiles, compileCp, classes)
+            _.compileGroovyStubs(groovySourceFiles, compileCp, classes, config)
           }
         workerStubResult match {
           case Result.Success(_) => compileJava
@@ -165,7 +195,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
 
         val workerGroovyResult =
           GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
-            _.compile(groovySourceFiles, compileCp, classes)
+            _.compile(groovySourceFiles, compileCp, classes, config)
           }
 
         // TODO figure out if there is a better way to do this
diff --git a/libs/groovylib/src/mill/groovylib/publish/exports.scala b/libs/groovylib/src/mill/groovylib/publish/exports.scala
index 8224e34c4956..0c01da54c719 100644
--- a/libs/groovylib/src/mill/groovylib/publish/exports.scala
+++ b/libs/groovylib/src/mill/groovylib/publish/exports.scala
@@ -26,7 +26,7 @@ export mill.javalib.publish.PackagingType
 
 export mill.javalib.publish.SonatypeHelpers
 export mill.javalib.publish.SonatypeHttpApi
-export mill.javalib.publish.SonatypePublisher
+export mill.javalib.SonatypeCentralPublisher
 
 export mill.javalib.publish.VersionControl
 
diff --git a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
index 391ac9a702dd..c4f60b525b8d 100644
--- a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
+++ b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
@@ -4,7 +4,7 @@ import groovy.lang.GroovyClassLoader
 import mill.api.Result
 import mill.api.TaskCtx
 import mill.javalib.api.CompilationResult
-import mill.groovylib.worker.api.GroovyWorker
+import mill.groovylib.worker.api.{GroovyCompilerConfiguration, GroovyWorker}
 import org.codehaus.groovy.control.{CompilationUnit, CompilerConfiguration, Phases}
 import org.codehaus.groovy.tools.javac.JavaStubCompilationUnit
 import os.Path
@@ -17,22 +17,26 @@ class GroovyWorkerImpl extends GroovyWorker {
   override def compileGroovyStubs(
       sourceFiles: Seq[Path],
       classpath: Seq[Path],
-      outputDir: Path
+      outputDir: Path,
+      config: GroovyCompilerConfiguration,
   )(implicit ctx: TaskCtx): Result[CompilationResult] = {
-    val config = new CompilerConfiguration()
-    config.setTargetDirectory(outputDir.toIO)
-    config.setClasspathList(classpath.map(_.toIO.getAbsolutePath).asJava)
-    config.setJointCompilationOptions(Map(
+    val compilerConfig = new CompilerConfiguration()
+    compilerConfig.setTargetDirectory(outputDir.toIO)
+    compilerConfig.setClasspathList(classpath.map(_.toIO.getAbsolutePath).asJava)
+    compilerConfig.setJointCompilationOptions(Map(
       "stubDir" -> outputDir.toIO,
       "keepStubs" -> false
     ).asJava)
+    compilerConfig.setDisabledGlobalASTTransformations(config.disabledGlobalAstTransformations.asJava)
+    compilerConfig.setPreviewFeatures(config.enablePreview)
+    config.targetBytecode.foreach(compilerConfig.setTargetBytecode)
 
     // we need to set the classloader for groovy to use the worker classloader
     val parentCl: ClassLoader = this.getClass.getClassLoader
-    // config in the GroovyClassLoader is needed when the CL itself is compiling classes
-    val gcl = new GroovyClassLoader(parentCl, config)
-    // config for actual compilation
-    val stubUnit = JavaStubCompilationUnit(config, gcl)
+    // compilerConfig in the GroovyClassLoader is needed when the CL itself is compiling classes
+    val gcl = new GroovyClassLoader(parentCl, compilerConfig)
+    // compilerConfig for actual compilation
+    val stubUnit = JavaStubCompilationUnit(compilerConfig, gcl)
 
     sourceFiles.foreach { sourceFile =>
       stubUnit.addSource(sourceFile.toIO)
@@ -51,26 +55,28 @@ class GroovyWorkerImpl extends GroovyWorker {
   def compile(
       sourceFiles: Seq[os.Path],
       classpath: Seq[os.Path],
-      outputDir: os.Path
+      outputDir: os.Path,
+      config: GroovyCompilerConfiguration,
   )(implicit
       ctx: TaskCtx
   ): Result[CompilationResult] = {
 
     val extendedClasspath = classpath :+ outputDir
 
-    val config = new CompilerConfiguration()
-    config.setTargetDirectory(outputDir.toIO)
-    config.setClasspathList(extendedClasspath.map(_.toIO.getAbsolutePath).asJava)
-    // TODO
-//    config.setDisabledGlobalASTTransformations()
-//    config.setSourceEncoding()
+    val compilerConfig = new CompilerConfiguration()
+    compilerConfig.setTargetDirectory(outputDir.toIO)
+    compilerConfig.setClasspathList(extendedClasspath.map(_.toIO.getAbsolutePath).asJava)
+    compilerConfig.setDisabledGlobalASTTransformations(config.disabledGlobalAstTransformations.asJava)
+    compilerConfig.setPreviewFeatures(config.enablePreview)
+    config.targetBytecode.foreach(compilerConfig.setTargetBytecode)
 
     // we need to set the classloader for groovy to use the worker classloader
     val parentCl: ClassLoader = this.getClass.getClassLoader
-    // config in the GroovyClassLoader is needed when the CL itself is compiling classes
-    val gcl = new GroovyClassLoader(parentCl, config)
-    // config for actual compilation
-    val unit = new CompilationUnit(config, null, gcl)
+    // compilerConfig in the GroovyClassLoader is needed when the CL itself is compiling classes
+    val gcl = new GroovyClassLoader(parentCl, compilerConfig)
+
+    // compilerConfig for actual compilation
+    val unit = new CompilationUnit(compilerConfig, null, gcl)
 
     sourceFiles.foreach { sourceFile =>
       unit.addSource(sourceFile.toIO)

From 507b11b5697ed9b5105a4677b5e2e935754e24a2 Mon Sep 17 00:00:00 2001
From: "autofix-ci[bot]" <114827586+autofix-ci[bot]@users.noreply.github.com>
Date: Wed, 24 Sep 2025 12:56:28 +0000
Subject: [PATCH 11/23] [autofix.ci] apply automated fixes

---
 .../worker/api/GroovyCompilerConfiguration.scala     |  9 +++++----
 libs/groovylib/src/mill/groovylib/GroovyModule.scala |  3 +--
 .../groovylib/worker/impl/GroovyWorkerImpl.scala     | 12 ++++++++----
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala
index 414bfbe6e13d..7c4d7dee5bd2 100644
--- a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala
@@ -1,6 +1,7 @@
 package mill.groovylib.worker.api
 
-case class GroovyCompilerConfiguration (
-  enablePreview: Boolean = false,
-  disabledGlobalAstTransformations: Set[String]= Set.empty,
-  targetBytecode: Option[String]= None)
+case class GroovyCompilerConfiguration(
+    enablePreview: Boolean = false,
+    disabledGlobalAstTransformations: Set[String] = Set.empty,
+    targetBytecode: Option[String] = None
+)
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 555747846885..87f957cd5240 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -72,7 +72,6 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    */
   def disabledGlobalAstTransformations: T[Set[String]] = Set.empty
 
-
   /**
    * All individual Java source files fed into the compiler.
    * Subset of [[allSourceFiles]].
@@ -155,7 +154,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
       val config = GroovyCompilerConfiguration(
         enablePreview = enablePreview(),
         targetBytecode = targetBytecode(),
-        disabledGlobalAstTransformations = disabledGlobalAstTransformations(),
+        disabledGlobalAstTransformations = disabledGlobalAstTransformations()
       )
 
       def compileJava: Result[CompilationResult] = {
diff --git a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
index c4f60b525b8d..14cb20330fd3 100644
--- a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
+++ b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
@@ -18,7 +18,7 @@ class GroovyWorkerImpl extends GroovyWorker {
       sourceFiles: Seq[Path],
       classpath: Seq[Path],
       outputDir: Path,
-      config: GroovyCompilerConfiguration,
+      config: GroovyCompilerConfiguration
   )(implicit ctx: TaskCtx): Result[CompilationResult] = {
     val compilerConfig = new CompilerConfiguration()
     compilerConfig.setTargetDirectory(outputDir.toIO)
@@ -27,7 +27,9 @@ class GroovyWorkerImpl extends GroovyWorker {
       "stubDir" -> outputDir.toIO,
       "keepStubs" -> false
     ).asJava)
-    compilerConfig.setDisabledGlobalASTTransformations(config.disabledGlobalAstTransformations.asJava)
+    compilerConfig.setDisabledGlobalASTTransformations(
+      config.disabledGlobalAstTransformations.asJava
+    )
     compilerConfig.setPreviewFeatures(config.enablePreview)
     config.targetBytecode.foreach(compilerConfig.setTargetBytecode)
 
@@ -56,7 +58,7 @@ class GroovyWorkerImpl extends GroovyWorker {
       sourceFiles: Seq[os.Path],
       classpath: Seq[os.Path],
       outputDir: os.Path,
-      config: GroovyCompilerConfiguration,
+      config: GroovyCompilerConfiguration
   )(implicit
       ctx: TaskCtx
   ): Result[CompilationResult] = {
@@ -66,7 +68,9 @@ class GroovyWorkerImpl extends GroovyWorker {
     val compilerConfig = new CompilerConfiguration()
     compilerConfig.setTargetDirectory(outputDir.toIO)
     compilerConfig.setClasspathList(extendedClasspath.map(_.toIO.getAbsolutePath).asJava)
-    compilerConfig.setDisabledGlobalASTTransformations(config.disabledGlobalAstTransformations.asJava)
+    compilerConfig.setDisabledGlobalASTTransformations(
+      config.disabledGlobalAstTransformations.asJava
+    )
     compilerConfig.setPreviewFeatures(config.enablePreview)
     config.targetBytecode.foreach(compilerConfig.setTargetBytecode)
 

From e218ec2710e74bc1696f5e92d5e1c48b786058b7 Mon Sep 17 00:00:00 2001
From: Tobias Roeser <le.petit.fou@web.de>
Date: Fri, 26 Sep 2025 11:59:19 +0200
Subject: [PATCH 12/23] Added example tests to CI setup

---
 .github/workflows/run-tests.yml | 4 ++++
 example/package.mill            | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index d42d89e5a843..0eb23fbf7164 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -154,6 +154,10 @@ jobs:
             millargs: "'example.androidlib.__.local.daemon'"
             setup-android: true
 
+          - java-version: 17
+            millargs: "'example.groovylib.__.local.daemon'"
+            setup-android: true
+
           - java-version: 17
             millargs: "'example.thirdparty[androidtodo].packaged.daemon'"
             setup-android: true
diff --git a/example/package.mill b/example/package.mill
index df36b154cdcb..197641a1cbcf 100644
--- a/example/package.mill
+++ b/example/package.mill
@@ -80,6 +80,11 @@ object `package` extends Module {
     object testing extends Cross[ExampleCrossModule](build.listCross)
   }
 
+  object groovylib extends Module {
+    object basic extends Cross[ExampleCrossModule](build.listCross)
+    object testing extends Cross[ExampleCrossModule](build.listCross)
+  }
+
   object cli extends Module {
     object builtins extends Cross[ExampleCrossModule](build.listCross)
     object header extends Cross[ExampleCrossModule](build.listCross)

From 485a8c37465b01c4fb006831ad8e4f3c67409419 Mon Sep 17 00:00:00 2001
From: Tobias Roeser <le.petit.fou@web.de>
Date: Fri, 26 Sep 2025 14:29:47 +0200
Subject: [PATCH 13/23] Rudimentarily fix webpage generation

---
 website/docs/modules/ROOT/nav.adoc            |  2 ++
 .../modules/ROOT/pages/groovylib/intro.adoc   | 25 +++++++++++++++++--
 .../modules/ROOT/pages/groovylib/testing.adoc |  3 +--
 3 files changed, 26 insertions(+), 4 deletions(-)

diff --git a/website/docs/modules/ROOT/nav.adoc b/website/docs/modules/ROOT/nav.adoc
index f45eb00f8263..00fe57a1a365 100644
--- a/website/docs/modules/ROOT/nav.adoc
+++ b/website/docs/modules/ROOT/nav.adoc
@@ -57,6 +57,8 @@
 *** xref:javascriptlib/linting.adoc[]
 *** xref:javascriptlib/publishing.adoc[]
 *** xref:javascriptlib/build-examples.adoc[]
+** xref:groovylib/intro.adoc[]
+*** xref:groovylib/testing.adoc[]
 * xref:comparisons/why-mill.adoc[]
 ** xref:comparisons/maven.adoc[]
 ** xref:comparisons/gradle.adoc[]
diff --git a/website/docs/modules/ROOT/pages/groovylib/intro.adoc b/website/docs/modules/ROOT/pages/groovylib/intro.adoc
index 0538fa008d79..cab3270bd64f 100644
--- a/website/docs/modules/ROOT/pages/groovylib/intro.adoc
+++ b/website/docs/modules/ROOT/pages/groovylib/intro.adoc
@@ -1,10 +1,31 @@
-
 = Building Groovy with Mill
 :page-aliases: Groovy_Intro_to_Mill.adoc
 :language: Groovy
 :language-small: groovy
 
-include::partial$Intro_Header.adoc[]
+// START-COPY-AND-PASTE
+// Instead of this include
+// include::partial$Intro_Header.adoc[]
+// We copy the text here, as we currently have no publishing page
+
+This page contains a quick introduction to getting start with using Mill to build
+a simple {language} program. It walks through a series of Mill builds of increasing
+complexity to show you the key features and usage of the Mill build tool.
+The other pages of this section of the docs go into more depth into individual Mill features.
+These aren't intended to be read comprehensively top-to-bottom, but
+rather looked up when you have a particular interest e.g. in
+xref:{language-small}lib/testing.adoc[testing],
+xref:javalib/publishing.adoc[publishing], and so on.
+
+The API reference for Mill's {language} toolchain can be found at:
+
+* {mill-doc-url}/api/latest/mill/{language-small}lib.html[mill.{language-small}lib]
+
+If you aren't sure why you would use Mill, see xref:comparisons/why-mill.adoc[] for
+a discussion on the motivations of the project. If you are migrating an existing project,
+see xref:migrating/migrating.adoc[Migrating to Mill].
+
+// END-COPY-AND-PASTE
 
 NOTE: Mill Groovy support is currently still under active development.
 It is expected to continue evolving over time.
diff --git a/website/docs/modules/ROOT/pages/groovylib/testing.adoc b/website/docs/modules/ROOT/pages/groovylib/testing.adoc
index 47296507879b..c8577c468e96 100644
--- a/website/docs/modules/ROOT/pages/groovylib/testing.adoc
+++ b/website/docs/modules/ROOT/pages/groovylib/testing.adoc
@@ -2,7 +2,6 @@
 :page-aliases: Testing_Groovy_Projects.adoc
 
 
-
 This page will discuss common topics around working with test suites using the Mill build tool
 
 == Defining Unit Test Suites
@@ -19,7 +18,7 @@ include::partial$example/groovylib/testing/3-spock.adoc[]
 
 == Using Spock in Java projects with Maven layout
 
-include::partial$example/groovylib/testing/4-java-spock.adoc[]
+include::partial$example/groovylib/testing/4-spock-for-java.adoc[]
 
 == Github Actions Test Reports
 

From f0cc0b8645dc8c79099c37f317d918a92442dd3f Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Fri, 26 Sep 2025 15:43:12 +0200
Subject: [PATCH 14/23] Cleanup and Testcase for targetBytecode and
 previewEnabled

---
 libs/groovylib/package.mill                   |  4 ++
 .../src/mill/groovylib/GroovyModule.scala     | 26 ++++++----
 .../src/HelloCompilerOptions.groovy           | 12 +++++
 .../src/mill/groovylib/HelloGroovyTests.scala | 52 +++++++++++++++++++
 4 files changed, 83 insertions(+), 11 deletions(-)
 create mode 100644 libs/groovylib/test/resources/hello-groovy/main/compileroptions/src/HelloCompilerOptions.groovy

diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index e9720db4ff65..dad2483fef1a 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -11,6 +11,10 @@ object `package` extends MillPublishScalaModule with BuildInfo {
   def localTestExtraModules: Seq[MillJavaModule] =
     super.localTestExtraModules ++ Seq(worker)
 
+  override def testMvnDeps: T[Seq[Dep]] = super.testMvnDeps() ++ Seq(
+    Deps.asmTree
+  )
+  
   def buildInfoPackageName = "mill.groovylib"
   def buildInfoObjectName = "Versions"
   def buildInfoMembers = Seq(
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 87f957cd5240..f0941da4c306 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -174,24 +174,17 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
         )
       }
 
-      if (isMixed) {
+      def compileGroovyStubs(): Result[CompilationResult] = {
         ctx.log.info("Compiling Groovy stubs for mixed compilation")
-
-        val workerStubResult =
-          GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
-            _.compileGroovyStubs(groovySourceFiles, compileCp, classes, config)
-          }
-        workerStubResult match {
-          case Result.Success(_) => compileJava
-          case Result.Failure(reason) => Result.Failure(reason)
+        GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
+          _.compileGroovyStubs(groovySourceFiles, compileCp, classes, config)
         }
       }
 
-      if (isMixed || isGroovy) {
+      def compileGroovy(): Result[CompilationResult] = {
         ctx.log.info(
           s"Compiling ${groovySourceFiles.size} Groovy sources to $classes ..."
         )
-
         val workerGroovyResult =
           GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
             _.compile(groovySourceFiles, compileCp, classes, config)
@@ -206,6 +199,17 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
             CompilationResult(analysisFile, PathRef(classes))
           case Result.Failure(reason) => Result.Failure(reason)
         }
+      }
+
+      val firstAndSecondStage = if (isMixed) {
+        // only compile Java if Stubs are successfully generated
+        compileGroovyStubs().flatMap(_ => compileJava)
+      }else{
+        Result.Success
+      }
+
+      if (isMixed || isGroovy) {
+        firstAndSecondStage.flatMap(_ => compileGroovy())
       } else {
         compileJava
       }
diff --git a/libs/groovylib/test/resources/hello-groovy/main/compileroptions/src/HelloCompilerOptions.groovy b/libs/groovylib/test/resources/hello-groovy/main/compileroptions/src/HelloCompilerOptions.groovy
new file mode 100644
index 000000000000..4033f7ae1fde
--- /dev/null
+++ b/libs/groovylib/test/resources/hello-groovy/main/compileroptions/src/HelloCompilerOptions.groovy
@@ -0,0 +1,12 @@
+package compileroptions
+
+class HelloCompilerOptions {
+
+    static String getHelloString() {
+        return "Hello, Java 11 Preview!"
+    }
+
+    static void main(String[] args) {
+        println(getHelloString())
+    }
+}
\ No newline at end of file
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index 740751799d52..06033420e132 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -7,6 +7,8 @@ import mill.api.Discover
 import mill.testkit.{TestRootModule, UnitTester}
 import utest.*
 
+import java.io.FileInputStream
+
 object HelloGroovyTests extends TestSuite {
 
   val groovy4Version = "4.0.28"
@@ -101,6 +103,13 @@ object HelloGroovyTests extends TestSuite {
         override def jupiterVersion: T[String] = junit5Version
         override def junitPlatformVersion = "1.13.4"
       }
+      
+      object compileroptions extends GroovyModule {
+        override def groovyVersion: T[String] = crossValue
+        override def targetBytecode: Task.Simple[Option[String]] = Some("11")
+        override def enablePreview: Task.Simple[Boolean] = true
+        override def mainClass = Some("compileroptions.HelloCompilerOptions")
+      }
     }
     object main extends Cross[Test](groovyVersions)
   }
@@ -195,6 +204,49 @@ object HelloGroovyTests extends TestSuite {
       }
     }
 
+    test("compiles to Java 11 with Preview enabled") {
+      import org.objectweb.asm.ClassReader
+
+      case class BytecodeVersion(major: Int, minor: Int) {
+        def javaVersion: String = major match {
+          case 55 => "11"
+          case _ => "Irrelevant"
+        }
+
+        def is11PreviewEnabled: Boolean = minor == 65535 // 0xFFFF
+      }
+
+      def getBytecodeVersion(classFilePath: os.Path): BytecodeVersion = {
+        val classReader = new ClassReader(new FileInputStream(classFilePath.toIO))
+        val buffer = classReader.b
+
+        // Class file format: magic(4) + minor(2) + major(2) + ...
+        val minor = ((buffer(4) & 0xFF) << 8) | (buffer(5) & 0xFF)
+        val major = ((buffer(6) & 0xFF) << 8) | (buffer(7) & 0xFF)
+
+        BytecodeVersion(major, minor)
+      }
+
+      testEval().scoped { eval =>
+        main.crossModules.foreach(m => {
+          val Right(result) = eval.apply(m.compileroptions.compile): @unchecked
+
+          val compiledClassFile = os.walk(result.value.classes.path).find(_.last == "HelloCompilerOptions.class")
+          
+          assert(
+            compiledClassFile.isDefined
+          )
+
+          val bytecodeVersion = getBytecodeVersion(compiledClassFile.get)
+
+          assert(bytecodeVersion.major == 55)
+          assert(bytecodeVersion.is11PreviewEnabled)
+          
+          val Right(_) = eval.apply(m.compileroptions.run()): @unchecked
+        })
+      }
+    }
+
     test("compile & test module (only test uses Groovy)") {
       testEval().scoped { eval =>
 

From 48b6020702ac578ce0c652d2970d1a13a09e1247 Mon Sep 17 00:00:00 2001
From: "autofix-ci[bot]" <114827586+autofix-ci[bot]@users.noreply.github.com>
Date: Fri, 26 Sep 2025 13:52:15 +0000
Subject: [PATCH 15/23] [autofix.ci] apply automated fixes

---
 libs/groovylib/package.mill                         |  2 +-
 .../groovylib/src/mill/groovylib/GroovyModule.scala |  2 +-
 .../test/src/mill/groovylib/HelloGroovyTests.scala  | 13 +++++++------
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index dad2483fef1a..e79c1a7737a4 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -14,7 +14,7 @@ object `package` extends MillPublishScalaModule with BuildInfo {
   override def testMvnDeps: T[Seq[Dep]] = super.testMvnDeps() ++ Seq(
     Deps.asmTree
   )
-  
+
   def buildInfoPackageName = "mill.groovylib"
   def buildInfoObjectName = "Versions"
   def buildInfoMembers = Seq(
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index f0941da4c306..784e5673dd09 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -204,7 +204,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
       val firstAndSecondStage = if (isMixed) {
         // only compile Java if Stubs are successfully generated
         compileGroovyStubs().flatMap(_ => compileJava)
-      }else{
+      } else {
         Result.Success
       }
 
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index 06033420e132..dcc3d4c0cc26 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -103,7 +103,7 @@ object HelloGroovyTests extends TestSuite {
         override def jupiterVersion: T[String] = junit5Version
         override def junitPlatformVersion = "1.13.4"
       }
-      
+
       object compileroptions extends GroovyModule {
         override def groovyVersion: T[String] = crossValue
         override def targetBytecode: Task.Simple[Option[String]] = Some("11")
@@ -221,8 +221,8 @@ object HelloGroovyTests extends TestSuite {
         val buffer = classReader.b
 
         // Class file format: magic(4) + minor(2) + major(2) + ...
-        val minor = ((buffer(4) & 0xFF) << 8) | (buffer(5) & 0xFF)
-        val major = ((buffer(6) & 0xFF) << 8) | (buffer(7) & 0xFF)
+        val minor = ((buffer(4) & 0xff) << 8) | (buffer(5) & 0xff)
+        val major = ((buffer(6) & 0xff) << 8) | (buffer(7) & 0xff)
 
         BytecodeVersion(major, minor)
       }
@@ -231,8 +231,9 @@ object HelloGroovyTests extends TestSuite {
         main.crossModules.foreach(m => {
           val Right(result) = eval.apply(m.compileroptions.compile): @unchecked
 
-          val compiledClassFile = os.walk(result.value.classes.path).find(_.last == "HelloCompilerOptions.class")
-          
+          val compiledClassFile =
+            os.walk(result.value.classes.path).find(_.last == "HelloCompilerOptions.class")
+
           assert(
             compiledClassFile.isDefined
           )
@@ -241,7 +242,7 @@ object HelloGroovyTests extends TestSuite {
 
           assert(bytecodeVersion.major == 55)
           assert(bytecodeVersion.is11PreviewEnabled)
-          
+
           val Right(_) = eval.apply(m.compileroptions.run()): @unchecked
         })
       }

From 21cf8f746cc92ad83f752e0d95a0a30ec008517d Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Fri, 26 Sep 2025 16:07:50 +0200
Subject: [PATCH 16/23] minor test improvement

---
 .../test/src/mill/groovylib/HelloGroovyTests.scala          | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index dcc3d4c0cc26..504aae783aad 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -105,8 +105,9 @@ object HelloGroovyTests extends TestSuite {
       }
 
       object compileroptions extends GroovyModule {
+        def javaVersion = "11"
         override def groovyVersion: T[String] = crossValue
-        override def targetBytecode: Task.Simple[Option[String]] = Some("11")
+        override def targetBytecode: Task.Simple[Option[String]] = Some(javaVersion)
         override def enablePreview: Task.Simple[Boolean] = true
         override def mainClass = Some("compileroptions.HelloCompilerOptions")
       }
@@ -220,6 +221,7 @@ object HelloGroovyTests extends TestSuite {
         val classReader = new ClassReader(new FileInputStream(classFilePath.toIO))
         val buffer = classReader.b
 
+        // see https://en.wikipedia.org/wiki/Java_class_file#General_layout
         // Class file format: magic(4) + minor(2) + major(2) + ...
         val minor = ((buffer(4) & 0xff) << 8) | (buffer(5) & 0xff)
         val major = ((buffer(6) & 0xff) << 8) | (buffer(7) & 0xff)
@@ -240,7 +242,7 @@ object HelloGroovyTests extends TestSuite {
 
           val bytecodeVersion = getBytecodeVersion(compiledClassFile.get)
 
-          assert(bytecodeVersion.major == 55)
+          assert(bytecodeVersion.javaVersion == m.compileroptions.javaVersion)
           assert(bytecodeVersion.is11PreviewEnabled)
 
           val Right(_) = eval.apply(m.compileroptions.run()): @unchecked

From 0df8825b943e657d20c3f325b767274c0efa472e Mon Sep 17 00:00:00 2001
From: Tobias Roeser <le.petit.fou@web.de>
Date: Sat, 27 Sep 2025 10:03:32 +0200
Subject: [PATCH 17/23] Mark API as experimental

---
 .../worker/api/GroovyCompilerConfiguration.scala     |  1 +
 .../src/mill/groovylib/worker/api/GroovyWorker.scala |  1 +
 libs/groovylib/package.mill                          | 12 +++---------
 .../src/mill/groovylib/GroovyMavenModule.scala       |  1 +
 libs/groovylib/src/mill/groovylib/GroovyModule.scala |  1 +
 .../src/mill/groovylib/GroovyWorkerManager.scala     |  1 +
 .../groovylib/JavaMavenModuleWithGroovyTests.scala   |  1 +
 7 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala
index 7c4d7dee5bd2..0206c3d2d4fe 100644
--- a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyCompilerConfiguration.scala
@@ -1,5 +1,6 @@
 package mill.groovylib.worker.api
 
+@mill.api.experimental
 case class GroovyCompilerConfiguration(
     enablePreview: Boolean = false,
     disabledGlobalAstTransformations: Set[String] = Set.empty,
diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
index 32a7493f44d2..8a2f40849ffd 100644
--- a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
@@ -11,6 +11,7 @@ import mill.javalib.api.CompilationResult
  * 2. compile Java sources (done externally)
  * 3. compile Groovy sources
  */
+@mill.api.experimental
 trait GroovyWorker {
 
   /**
diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index e79c1a7737a4..028e1a97dba9 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -5,7 +5,7 @@ import mill.contrib.buildinfo.BuildInfo
 import mill.scalalib.*
 import millbuild.*
 
-object `package` extends MillPublishScalaModule with BuildInfo {
+object `package` extends MillStableScalaModule with BuildInfo {
 
   def moduleDeps = Seq(build.libs.util, build.libs.javalib, build.libs.javalib.testrunner, api)
   def localTestExtraModules: Seq[MillJavaModule] =
@@ -21,13 +21,7 @@ object `package` extends MillPublishScalaModule with BuildInfo {
     BuildInfo.Value("groovyVersion", Deps.groovyVersion, "Version of Groovy")
   )
 
-  trait MillGroovyModule extends MillPublishScalaModule {
-    override def javacOptions = super.javacOptions() ++ {
-      Seq("-release", "8", "-encoding", "UTF-8", "-deprecation")
-    }
-  }
-
-  object api extends MillGroovyModule {
+  object api extends MillStableScalaModule {
     def moduleDeps = Seq(build.libs.javalib.testrunner)
 
     override def compileMvnDeps: T[Seq[Dep]] = Seq(
@@ -35,7 +29,7 @@ object `package` extends MillPublishScalaModule with BuildInfo {
     )
   }
 
-  object worker extends MillGroovyModule {
+  object worker extends MillPublishScalaModule {
     override def compileModuleDeps = Seq(api)
 
     def mandatoryMvnDeps = Seq.empty[Dep]
diff --git a/libs/groovylib/src/mill/groovylib/GroovyMavenModule.scala b/libs/groovylib/src/mill/groovylib/GroovyMavenModule.scala
index bfcabb3bee9e..46c7ec366602 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyMavenModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyMavenModule.scala
@@ -7,6 +7,7 @@ import mill.javalib.MavenModule
  * A [[GroovyModule]] with a Maven compatible directory layout:
  * `src/main/groovy`, `src/main/resources`, etc.
  */
+@mill.api.experimental
 trait GroovyMavenModule extends GroovyModule with MavenModule {
   private def sources0 = Task.Sources("src/main/groovy")
   override def sources = super.sources() ++ sources0()
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 784e5673dd09..681f26f70a3d 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -18,6 +18,7 @@ import mill.util.Version
  *
  * Resolves
  */
+@mill.api.experimental
 trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
 
   /**
diff --git a/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala b/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
index 292d5290dd4b..41a85025df9c 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyWorkerManager.scala
@@ -5,6 +5,7 @@ import mill.api.{Discover, ExternalModule, TaskCtx}
 import mill.groovylib.worker.api.GroovyWorker
 import mill.util.ClassLoaderCachedFactory
 
+@mill.api.experimental
 class GroovyWorkerManager()(implicit ctx: TaskCtx)
     extends ClassLoaderCachedFactory[GroovyWorker](ctx.jobs) {
 
diff --git a/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala b/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
index c7018dcca885..6b7f48e81edd 100644
--- a/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
+++ b/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
@@ -6,6 +6,7 @@ import mill.javalib.{JavaModule, MavenModule}
 /**
  * Convenience trait for projects using Java for production and Groovy for tests in a Maven setup
  */
+@mill.api.experimental
 trait JavaMavenModuleWithGroovyTests extends JavaModule with MavenModule {
 
   trait GroovyMavenTests extends JavaTests with MavenTests with GroovyModule {

From 2c80e4b4a03e455a6062583ce63c5a3e2595e982 Mon Sep 17 00:00:00 2001
From: Tobias Roeser <le.petit.fou@web.de>
Date: Sat, 27 Sep 2025 10:41:08 +0200
Subject: [PATCH 18/23] Fix mima setup

---
 libs/groovylib/package.mill | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index 028e1a97dba9..711fdcd29530 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -21,7 +21,12 @@ object `package` extends MillStableScalaModule with BuildInfo {
     BuildInfo.Value("groovyVersion", Deps.groovyVersion, "Version of Groovy")
   )
 
-  object api extends MillStableScalaModule {
+  // this module wasn't released in these versions
+  def mimaPreviousVersions: T[Seq[String]] = super.mimaPreviousVersions().filterNot(
+    Seq("1.0.0", "1.0.1", "1.0.2", "1.0.3", "1.0.4", "1.0.5").contains
+  )
+
+  object api extends MillPublishScalaModule {
     def moduleDeps = Seq(build.libs.javalib.testrunner)
 
     override def compileMvnDeps: T[Seq[Dep]] = Seq(

From d2326842c548d80924a96a9c0ec3397034d9a857 Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Mon, 29 Sep 2025 09:33:59 +0200
Subject: [PATCH 19/23] minor review remarks

---
 .../src/mill/groovylib/GroovyModule.scala     | 14 ++++++-------
 .../JavaMavenModuleWithGroovyTests.scala      | 20 ++++++++++++++++++-
 .../src/mill/groovylib/HelloGroovyTests.scala |  4 ++--
 .../javalib/src/mill/javalib/TestModule.scala |  6 +++---
 4 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 681f26f70a3d..8bcb27074913 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -31,7 +31,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
    */
   def groovyLanguageVersion: T[String] = Task { groovyVersion().split("[.]").take(2).mkString(".") }
 
-  private def isGroovyBomAvailable: T[Boolean] = Task {
+  private def useGroovyBom: T[Boolean] = Task {
     if (groovyVersion().isBlank) {
       false
     } else {
@@ -41,7 +41,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
 
   override def bomMvnDeps: T[Seq[Dep]] = super.bomMvnDeps() ++
     Seq(groovyVersion())
-      .filter(_.nonEmpty && isGroovyBomAvailable())
+      .filter(_.nonEmpty && useGroovyBom())
       .map(v => mvn"org.apache.groovy:groovy-bom:$v")
 
   /**
@@ -54,15 +54,15 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
   /**
    * Specifiy the bytecode version for the Groovy compiler.
    * {{{
-   *   def targetBytecode = Some("17")
+   *   def groovyCompileTargetBytecode = Some("17")
    * }}}
    */
-  def targetBytecode: T[Option[String]] = None
+  def groovyCompileTargetBytecode: T[Option[String]] = None
 
   /**
    * Specify if the Groovy compiler should enable preview features.
    */
-  def enablePreview: T[Boolean] = false
+  def groovyCompileEnablePreview: T[Boolean] = false
 
   /**
    * Specify which global AST transformations should be disabled. Be aware that transformations
@@ -153,8 +153,8 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
       val updateCompileOutput = upstreamCompileOutput()
 
       val config = GroovyCompilerConfiguration(
-        enablePreview = enablePreview(),
-        targetBytecode = targetBytecode(),
+        enablePreview = groovyCompileEnablePreview(),
+        targetBytecode = groovyCompileTargetBytecode(),
         disabledGlobalAstTransformations = disabledGlobalAstTransformations()
       )
 
diff --git a/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala b/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
index 6b7f48e81edd..958483a1936a 100644
--- a/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
+++ b/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
@@ -4,7 +4,25 @@ import mill.*
 import mill.javalib.{JavaModule, MavenModule}
 
 /**
- * Convenience trait for projects using Java for production and Groovy for tests in a Maven setup
+ * Convenience trait for projects using Java for production and Groovy for tests in a Maven setup.
+ * 
+ * Since [[GroovyModule.GroovyTests]] is only available as a child-trait, it is necessary to have
+ * the main module as a [[GroovyModule]], which would implicitly add Groovy dependencies to the 
+ * module.
+ * This trait explicitly uses Java with a Maven layout for the main module and enables `src/test/groovy`
+ * as a source folder for Groovy tests.
+ * 
+ * {{{
+ *     object `package` extends JavaMavenModuleWithGroovyTests {
+ *
+ *       object `test` extends GroovyMavenTests with TestModule.Spock {
+ *         override def groovyVersion: T[String] = "4.0.28"
+ *         override def spockVersion: T[String] = "2.3-groovy-4"
+ *       }
+ *     }
+ * }}}
+ * 
+ * Note: for non-Maven layouts this is not necessary, since the test module can just be a [[GroovyModule]].
  */
 @mill.api.experimental
 trait JavaMavenModuleWithGroovyTests extends JavaModule with MavenModule {
diff --git a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
index 504aae783aad..6a07da866c30 100644
--- a/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
+++ b/libs/groovylib/test/src/mill/groovylib/HelloGroovyTests.scala
@@ -107,8 +107,8 @@ object HelloGroovyTests extends TestSuite {
       object compileroptions extends GroovyModule {
         def javaVersion = "11"
         override def groovyVersion: T[String] = crossValue
-        override def targetBytecode: Task.Simple[Option[String]] = Some(javaVersion)
-        override def enablePreview: Task.Simple[Boolean] = true
+        override def groovyCompileTargetBytecode: Task.Simple[Option[String]] = Some(javaVersion)
+        override def groovyCompileEnablePreview: Task.Simple[Boolean] = true
         override def mainClass = Some("compileroptions.HelloCompilerOptions")
       }
     }
diff --git a/libs/javalib/src/mill/javalib/TestModule.scala b/libs/javalib/src/mill/javalib/TestModule.scala
index f71196898b3b..8bcba0688842 100644
--- a/libs/javalib/src/mill/javalib/TestModule.scala
+++ b/libs/javalib/src/mill/javalib/TestModule.scala
@@ -372,7 +372,7 @@ object TestModule {
     /** The JUnit Jupiter version to use, or empty, if you want to provide the dependencies yourself. */
     def jupiterVersion: T[String] = Task { "" }
 
-    private def isJupiterBomAvailable: T[Boolean] = Task {
+    private def useJupiterBom: T[Boolean] = Task {
       if (jupiterVersion().isBlank) {
         false
       } else {
@@ -385,7 +385,7 @@ object TestModule {
     override def bomMvnDeps: T[Seq[Dep]] = Task {
       super.bomMvnDeps() ++
         Seq(jupiterVersion())
-          .filter(!_.isBlank() && isJupiterBomAvailable())
+          .filter(!_.isBlank() && useJupiterBom())
           .flatMap(v =>
             Seq(
               mvn"org.junit:junit-bom:${v.trim()}"
@@ -399,7 +399,7 @@ object TestModule {
         Seq(junitPlatformVersion()).flatMap(v => {
           if (!v.isBlank) {
             Some(mvn"org.junit.platform:junit-platform-launcher:${v.trim()}")
-          } else if (isJupiterBomAvailable()) {
+          } else if (useJupiterBom()) {
             Some(mvn"org.junit.platform:junit-platform-launcher")
           } else {
             None

From 7fac9ce2f9abfd63c9b4aaa37272476a92650b9e Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Mon, 29 Sep 2025 14:41:35 +0200
Subject: [PATCH 20/23] use Mill caching for stub folder

---
 .../groovylib/worker/api/GroovyWorker.scala   |  4 +-
 .../src/mill/groovylib/GroovyModule.scala     | 69 +++++++++++++------
 .../worker/impl/GroovyWorkerImpl.scala        | 19 ++---
 3 files changed, 54 insertions(+), 38 deletions(-)

diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
index 8a2f40849ffd..e4acb8198594 100644
--- a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
@@ -1,6 +1,6 @@
 package mill.groovylib.worker.api
 
-import mill.api.{Result, TaskCtx}
+import mill.api.{PathRef, Result, TaskCtx}
 import mill.javalib.api.CompilationResult
 
 /**
@@ -25,7 +25,7 @@ trait GroovyWorker {
   )(implicit
       ctx: TaskCtx
   )
-      : Result[CompilationResult]
+  : Result[Unit]
 
   /**
    * Compiles the Groovy sources. In a mixed setup this method assumes that the Java stubs
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index 8bcb27074913..cd747f615adc 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -132,6 +132,29 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
     groovyCompileTask()()
   }
 
+  def compileGroovyStubs: T[Result[Unit]] = Task(persistent = true){
+    val groovySourceFiles = allGroovySourceFiles().map(_.path)
+    val stubDir = compileGeneratedGroovyStubs()
+    Task.ctx().log.info(s"Generating Java stubs for ${groovySourceFiles.size} Groovy sources to $stubDir ...")
+
+    val compileCp = compileClasspath().map(_.path).filter(os.exists)
+    val config = GroovyCompilerConfiguration(
+      enablePreview = groovyCompileEnablePreview(),
+      targetBytecode = groovyCompileTargetBytecode(),
+      disabledGlobalAstTransformations = disabledGlobalAstTransformations()
+    )
+
+    GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
+      _.compileGroovyStubs(groovySourceFiles, compileCp, stubDir, config)
+    }
+  }
+
+  /**
+   * Path to Java stub sources as part of the `compile` step. Stubs are generated
+   * by the Groovy compiler and later used by the Java compiler.
+   */
+  def compileGeneratedGroovyStubs: T[os.Path] = Task(persistent = true) { Task.dest }
+
   /**
    * The actual Groovy compile task (used by [[compile]]).
    */
@@ -147,11 +170,21 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
 
       val isGroovy = groovySourceFiles.nonEmpty
       val isJava = javaSourceFiles.nonEmpty
-      val isMixed = isGroovy && isJava
-
       val compileCp = compileClasspath().map(_.path).filter(os.exists)
       val updateCompileOutput = upstreamCompileOutput()
 
+      sealed trait CompilationStrategy
+      case object JavaOnly extends CompilationStrategy
+      case object GroovyOnly extends CompilationStrategy
+      case object Mixed extends CompilationStrategy
+
+      val strategy: CompilationStrategy = (isJava, isGroovy) match {
+        case (true, false) => JavaOnly
+        case (false, true) => GroovyOnly
+        case (true, true) => Mixed
+        case (false, false) => JavaOnly // fallback, though this shouldn't happen
+      }
+
       val config = GroovyCompilerConfiguration(
         enablePreview = groovyCompileEnablePreview(),
         targetBytecode = groovyCompileTargetBytecode(),
@@ -167,7 +200,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
           worker = jvmWorkerRef().internalWorker(),
           upstreamCompileOutput = updateCompileOutput,
           javaSourceFiles = javaSourceFiles,
-          compileCp = compileCp,
+          compileCp = compileCp :+ compileGeneratedGroovyStubs(),
           javaHome = javaHome().map(_.path),
           javacOptions = javacOptions(),
           compileProblemReporter = ctx.reporter(hashCode),
@@ -175,13 +208,6 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
         )
       }
 
-      def compileGroovyStubs(): Result[CompilationResult] = {
-        ctx.log.info("Compiling Groovy stubs for mixed compilation")
-        GroovyWorkerManager.groovyWorker().withValue(groovyCompilerClasspath()) {
-          _.compileGroovyStubs(groovySourceFiles, compileCp, classes, config)
-        }
-      }
-
       def compileGroovy(): Result[CompilationResult] = {
         ctx.log.info(
           s"Compiling ${groovySourceFiles.size} Groovy sources to $classes ..."
@@ -192,7 +218,7 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
           }
 
         // TODO figure out if there is a better way to do this
-        val analysisFile = dest / "groovy.analysis.dummy" // needed for mills CompilationResult
+        val analysisFile = dest / "groovy.analysis.dummy" // needed for Mills CompilationResult
         os.write(target = analysisFile, data = "", createFolders = true)
 
         workerGroovyResult match {
@@ -202,18 +228,19 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
         }
       }
 
-      val firstAndSecondStage = if (isMixed) {
-        // only compile Java if Stubs are successfully generated
-        compileGroovyStubs().flatMap(_ => compileJava)
-      } else {
-        Result.Success
-      }
+      strategy match {
+        case JavaOnly =>
+          compileJava
 
-      if (isMixed || isGroovy) {
-        firstAndSecondStage.flatMap(_ => compileGroovy())
-      } else {
-        compileJava
+        case GroovyOnly =>
+          compileGroovy()
+
+        case Mixed =>
+          compileGroovyStubs()
+            .flatMap(_ => compileJava)
+            .flatMap(_ => compileGroovy())
       }
+
     }
 
   private[groovylib] def internalCompileJavaFiles(
diff --git a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
index 14cb20330fd3..28dbc2ecc888 100644
--- a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
+++ b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
@@ -1,8 +1,7 @@
 package mill.groovylib.worker.impl
 
 import groovy.lang.GroovyClassLoader
-import mill.api.Result
-import mill.api.TaskCtx
+import mill.api.{PathRef, Result, TaskCtx}
 import mill.javalib.api.CompilationResult
 import mill.groovylib.worker.api.{GroovyCompilerConfiguration, GroovyWorker}
 import org.codehaus.groovy.control.{CompilationUnit, CompilerConfiguration, Phases}
@@ -19,13 +18,13 @@ class GroovyWorkerImpl extends GroovyWorker {
       classpath: Seq[Path],
       outputDir: Path,
       config: GroovyCompilerConfiguration
-  )(implicit ctx: TaskCtx): Result[CompilationResult] = {
+  )(implicit ctx: TaskCtx): Result[Unit] = {
     val compilerConfig = new CompilerConfiguration()
     compilerConfig.setTargetDirectory(outputDir.toIO)
     compilerConfig.setClasspathList(classpath.map(_.toIO.getAbsolutePath).asJava)
     compilerConfig.setJointCompilationOptions(Map(
       "stubDir" -> outputDir.toIO,
-      "keepStubs" -> false
+      "keepStubs" -> true
     ).asJava)
     compilerConfig.setDisabledGlobalASTTransformations(
       config.disabledGlobalAstTransformations.asJava
@@ -46,10 +45,9 @@ class GroovyWorkerImpl extends GroovyWorker {
 
     Try {
       stubUnit.compile(Phases.CONVERSION)
-      CompilationResult(outputDir, mill.api.PathRef(outputDir))
     }.fold(
       exception => Result.Failure(s"Groovy stub generation failed: ${exception.getMessage}"),
-      result => Result.Success(result)
+      result => Result.Success(())
     )
 
   }
@@ -88,19 +86,10 @@ class GroovyWorkerImpl extends GroovyWorker {
 
     Try {
       unit.compile(Phases.OUTPUT)
-      removeAllJavaFiles(outputDir)
       CompilationResult(outputDir, mill.api.PathRef(outputDir))
     }.fold(
       exception => Result.Failure(s"Groovy compilation failed: ${exception.getMessage}"),
       result => Result.Success(result)
     )
   }
-
-  private def removeAllJavaFiles(outputDir: os.Path): Unit = {
-    if (os.exists(outputDir)) {
-      os.walk(outputDir)
-        .filter(_.ext == "java")
-        .foreach(os.remove)
-    }
-  }
 }

From b5177adaee368ee9c0ad8038e5650997eb924b9e Mon Sep 17 00:00:00 2001
From: "autofix-ci[bot]" <114827586+autofix-ci[bot]@users.noreply.github.com>
Date: Mon, 29 Sep 2025 12:53:06 +0000
Subject: [PATCH 21/23] [autofix.ci] apply automated fixes

---
 .../api/src/mill/groovylib/worker/api/GroovyWorker.scala  | 4 ++--
 libs/groovylib/src/mill/groovylib/GroovyModule.scala      | 6 ++++--
 .../mill/groovylib/JavaMavenModuleWithGroovyTests.scala   | 8 ++++----
 .../src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala | 2 +-
 4 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
index e4acb8198594..ef1e8916e510 100644
--- a/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
+++ b/libs/groovylib/api/src/mill/groovylib/worker/api/GroovyWorker.scala
@@ -1,6 +1,6 @@
 package mill.groovylib.worker.api
 
-import mill.api.{PathRef, Result, TaskCtx}
+import mill.api.{Result, TaskCtx}
 import mill.javalib.api.CompilationResult
 
 /**
@@ -25,7 +25,7 @@ trait GroovyWorker {
   )(implicit
       ctx: TaskCtx
   )
-  : Result[Unit]
+      : Result[Unit]
 
   /**
    * Compiles the Groovy sources. In a mixed setup this method assumes that the Java stubs
diff --git a/libs/groovylib/src/mill/groovylib/GroovyModule.scala b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
index cd747f615adc..25c5af0817ba 100644
--- a/libs/groovylib/src/mill/groovylib/GroovyModule.scala
+++ b/libs/groovylib/src/mill/groovylib/GroovyModule.scala
@@ -132,10 +132,12 @@ trait GroovyModule extends JavaModule with GroovyModuleApi { outer =>
     groovyCompileTask()()
   }
 
-  def compileGroovyStubs: T[Result[Unit]] = Task(persistent = true){
+  def compileGroovyStubs: T[Result[Unit]] = Task(persistent = true) {
     val groovySourceFiles = allGroovySourceFiles().map(_.path)
     val stubDir = compileGeneratedGroovyStubs()
-    Task.ctx().log.info(s"Generating Java stubs for ${groovySourceFiles.size} Groovy sources to $stubDir ...")
+    Task.ctx().log.info(
+      s"Generating Java stubs for ${groovySourceFiles.size} Groovy sources to $stubDir ..."
+    )
 
     val compileCp = compileClasspath().map(_.path).filter(os.exists)
     val config = GroovyCompilerConfiguration(
diff --git a/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala b/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
index 958483a1936a..6f2c4ce7f391 100644
--- a/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
+++ b/libs/groovylib/src/mill/groovylib/JavaMavenModuleWithGroovyTests.scala
@@ -5,13 +5,13 @@ import mill.javalib.{JavaModule, MavenModule}
 
 /**
  * Convenience trait for projects using Java for production and Groovy for tests in a Maven setup.
- * 
+ *
  * Since [[GroovyModule.GroovyTests]] is only available as a child-trait, it is necessary to have
- * the main module as a [[GroovyModule]], which would implicitly add Groovy dependencies to the 
+ * the main module as a [[GroovyModule]], which would implicitly add Groovy dependencies to the
  * module.
  * This trait explicitly uses Java with a Maven layout for the main module and enables `src/test/groovy`
  * as a source folder for Groovy tests.
- * 
+ *
  * {{{
  *     object `package` extends JavaMavenModuleWithGroovyTests {
  *
@@ -21,7 +21,7 @@ import mill.javalib.{JavaModule, MavenModule}
  *       }
  *     }
  * }}}
- * 
+ *
  * Note: for non-Maven layouts this is not necessary, since the test module can just be a [[GroovyModule]].
  */
 @mill.api.experimental
diff --git a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
index 28dbc2ecc888..85c48f3f05cc 100644
--- a/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
+++ b/libs/groovylib/worker/src/mill/groovylib/worker/impl/GroovyWorkerImpl.scala
@@ -1,7 +1,7 @@
 package mill.groovylib.worker.impl
 
 import groovy.lang.GroovyClassLoader
-import mill.api.{PathRef, Result, TaskCtx}
+import mill.api.{Result, TaskCtx}
 import mill.javalib.api.CompilationResult
 import mill.groovylib.worker.api.{GroovyCompilerConfiguration, GroovyWorker}
 import org.codehaus.groovy.control.{CompilationUnit, CompilerConfiguration, Phases}

From eed6b588ad271204a117f06f681a1465af5156f5 Mon Sep 17 00:00:00 2001
From: Marc Schlegel <marc.schlegel@gmx.de>
Date: Mon, 13 Oct 2025 07:34:53 +0200
Subject: [PATCH 22/23] Revert back to experimental module

---
 libs/groovylib/package.mill | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index 711fdcd29530..6b52ab41e193 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -5,7 +5,7 @@ import mill.contrib.buildinfo.BuildInfo
 import mill.scalalib.*
 import millbuild.*
 
-object `package` extends MillStableScalaModule with BuildInfo {
+object `package` extends MillPublishScalaModule with BuildInfo {
 
   def moduleDeps = Seq(build.libs.util, build.libs.javalib, build.libs.javalib.testrunner, api)
   def localTestExtraModules: Seq[MillJavaModule] =
@@ -21,10 +21,6 @@ object `package` extends MillStableScalaModule with BuildInfo {
     BuildInfo.Value("groovyVersion", Deps.groovyVersion, "Version of Groovy")
   )
 
-  // this module wasn't released in these versions
-  def mimaPreviousVersions: T[Seq[String]] = super.mimaPreviousVersions().filterNot(
-    Seq("1.0.0", "1.0.1", "1.0.2", "1.0.3", "1.0.4", "1.0.5").contains
-  )
 
   object api extends MillPublishScalaModule {
     def moduleDeps = Seq(build.libs.javalib.testrunner)

From 00b68933753d35592954137e687f0a41c053759c Mon Sep 17 00:00:00 2001
From: "autofix-ci[bot]" <114827586+autofix-ci[bot]@users.noreply.github.com>
Date: Mon, 13 Oct 2025 05:44:04 +0000
Subject: [PATCH 23/23] [autofix.ci] apply automated fixes

---
 libs/groovylib/package.mill | 1 -
 1 file changed, 1 deletion(-)

diff --git a/libs/groovylib/package.mill b/libs/groovylib/package.mill
index 6b52ab41e193..281ab876a443 100644
--- a/libs/groovylib/package.mill
+++ b/libs/groovylib/package.mill
@@ -21,7 +21,6 @@ object `package` extends MillPublishScalaModule with BuildInfo {
     BuildInfo.Value("groovyVersion", Deps.groovyVersion, "Version of Groovy")
   )
 
-
   object api extends MillPublishScalaModule {
     def moduleDeps = Seq(build.libs.javalib.testrunner)