Android/hilt unit tests (#5169)

## Summary

Prove that we can run the architecture-sample unit tests

The major feature missing here is to allow for kotlin modules to mark
any internal modules they depend on as friend modules (there was already
an isolated case for KotlinTests and the main source code) . Following
how the shared-tests of architecture samples depends on app main module
and in turn tests depend on shared-tests and main sources (as they do) ,
I've covered the missing gaps to get everything to work properly.

## Features added

- Kotlin `-X-friend-paths` is now used depending on transitive module
deps, for AndroidKotlinModules (this can later be expanded to
KotlinModule too)
- An androidNamespace is required for internal libs to function
- Android manifest for internal libs/modules needs to add metadata to
the manifest too
- AndroidHiltSupport should also be available to all android modules,
not just apps

## Fixes

- The AndroidHiltTransformAsm was dropping the META-INF, but it is
required for `-X-friend-paths` to function , as the kotlin module
contains the symbols necessary for internal members to be available to
the depending modules
- Ironed out the usage of androidApplicationNamespace vs
androidApplicationId as their usage becomes clearer to me the more apps
we integrate - this is under development and I expect their usage to be
stabilised once build variants are added too

## Unlocked workflows

This PR proves the following to be working:
- Complex unit test setup with Hilt
- A shared android module (shared-tests) can be given as a dependency
(it's a dependency of `app.test` and `app.androidTest` which will be
wired in in a follow up PR)
- Android Kotlin internal and top level members can be used between
depended modules (app.test can use app top level members as app compiled
path is passed as a friend path)

## Previous work reference

This is a continuous development for supporting android worfklows using
Hilt and by extension Kotlin KSP features.

Previous related work items:
- #4759
- #4485
- #4557

## Kotlin build issue

Need to check why arrow is not building, but probably I'll move the
friend paths functionality to AndroidKotlinModule if I don't manage to
identify the issue for the time being

Due to the use of outer in KotlinTest
```
    override def kotlincOptions: T[Seq[String]] = Task {
      outer.kotlincOptions().filterNot(_.startsWith("-Xcommon-sources")) ++
        Seq(s"-Xfriend-paths=${outer.compile().classes.path.toString()}")
    }
```

The `-Xfriend-paths` are picked from the parent and not computed
properly (so the module that a kotlin test directly depends on is
missing. e.g.

```
-Xfriend-paths=/home/vnicolaou/mill/out/example/thirdparty/arrow/downloadedRepo.dest/arrow-bc9bf92cc98e01c21bdd2bf8640cf7db0f97204a/out/arrow-libs/core/arrow-annotations/jvm/compile.dest/classes,/home/vnicolaou/mill/out/example/thirdparty/arrow/downloadedRepo.dest/arrow-bc9bf92cc98e01c21bdd2bf8640cf7db0f97204a/out/arrow-libs/core/arrow-atomic/jvm/compile.dest/classes,/home/vnicolaou/mill/out/example/thirdparty/arrow/downloadedRepo.dest/arrow-bc9bf92cc98e01c21bdd2bf8640cf7db0f97204a/out/arrow-libs/core/arrow-core/jvm/compile.dest/classes
```

but the kotlinc friend paths are from the outer module

```
[
  "-Xfriend-paths=/home/vnicolaou/mill/out/example/thirdparty/arrow/downloadedRepo.dest/arrow-bc9bf92cc98e01c21bdd2bf8640cf7db0f97204a/out/arrow-libs/core/arrow-annotations/jvm/compile.dest/classes,/home/vnicolaou/mill/out/example/thirdparty/arrow/downloadedRepo.dest/arrow-bc9bf92cc98e01c21bdd2bf8640cf7db0f97204a/out/arrow-libs/core/arrow-atomic/jvm/compile.dest/classes,/home/vnicolaou/mill/out/example/thirdparty/arrow/downloadedRepo.dest/arrow-bc9bf92cc98e01c21bdd2bf8640cf7db0f97204a/out/arrow-libs/core/arrow-core/jvm/compile.dest/classes",
  "-Xexpect-actual-classes"
]
```

I'm not gonna handle this in this PR, instead I've moved this logic to
AndroidKotlinModule and we can deal with it at a later stage

Pull request: #5169

Author: vaslabs

example/thirdparty/androidtodo/build.mill

@@ -3,6 +3,15 @@ package build
 import mill._, androidlib._, kotlinlib._
 import hilt.AndroidHiltSupport
 
+object Versions {
+  val kotlinVersion = "2.0.21"
+  val kotlinLanguageVersion = "1.9"
+
+  val kspVersion = "1.0.28"
+  val androidCompileSdk = 35
+  val androidMinSdk = 26
+}
+
 // Create and configure an Android SDK module to manage Android SDK paths and tools.
 object androidSdkModule0 extends AndroidSdkModule {
   def buildToolsVersion = "35.0.0"
@@ -11,20 +20,19 @@ object androidSdkModule0 extends AndroidSdkModule {
 // Mill configuration for the Android Todo App project.
 object app extends AndroidAppKotlinModule with AndroidBuildConfig with AndroidHiltSupport {
 
-  def kotlinVersion = "2.0.21"
-  def kotlinLanguageVersion = "1.9"
-
-  def kspVersion = "1.0.28"
+  def kotlinVersion = Versions.kotlinVersion
+  def kotlinLanguageVersion = Versions.kotlinLanguageVersion
+  def kspVersion = Versions.kspVersion
 
   def androidApplicationNamespace = "com.example.android.architecture.blueprints.todoapp"
   // TODO change this to com.example.android.architecture.blueprints.main when mill supports build variants
   def androidApplicationId = "com.example.android.architecture.blueprints.todoapp"
 
   def androidSdkModule = mill.define.ModuleRef(androidSdkModule0)
 
-  def androidCompileSdk = 35
+  def androidCompileSdk = Versions.androidCompileSdk
 
-  def androidMinSdk = 26
+  def androidMinSdk = Versions.androidMinSdk
 
   def androidEnableCompose = true
 
@@ -73,28 +81,92 @@ object app extends AndroidAppKotlinModule with AndroidBuildConfig with AndroidHi
     mvn"com.google.dagger:hilt-android-compiler:2.56"
   )
 
-  def kotlincPluginMvnDeps: T[Seq[Dep]] = Task {
-    Seq(
-      mvn"org.jetbrains.kotlin:kotlin-compose-compiler-plugin-embeddable:${kotlinVersion()}"
+  object test extends AndroidAppKotlinTests with AndroidHiltSupport with TestModule.Junit4 {
+
+    def moduleDeps = super.moduleDeps ++ Seq(`shared-test`)
+
+    def androidEnableCompose = true
+
+    override def kspVersion = Versions.kspVersion
+
+    def kotlinSymbolProcessors: T[Seq[Dep]] = Seq(
+      mvn"androidx.room:room-compiler:2.6.1",
+      mvn"com.google.dagger:hilt-android-compiler:2.56"
     )
-  }
 
-  object test extends AndroidAppKotlinTests with TestModule.Junit4 {
     def mvnDeps = super.mvnDeps() ++ Seq(
-      mvn"junit:junit:4.13.2"
+      mvn"junit:junit:4.13.2",
+      mvn"androidx.arch.core:core-testing:2.2.0",
+      mvn"org.jetbrains.kotlinx:kotlinx-coroutines-android:1.9.0",
+      mvn"org.jetbrains.kotlinx:kotlinx-coroutines-test:1.9.0",
+      mvn"androidx.navigation:navigation-testing:2.8.5",
+      mvn"androidx.test.espresso:espresso-core:3.6.1",
+      mvn"androidx.test.espresso:espresso-contrib:3.6.1",
+      mvn"androidx.test.espresso:espresso-intents:3.6.1",
+      mvn"com.google.truth:truth:1.4.4",
+      mvn"androidx.compose:compose-bom:2024.12.01",
+      mvn"androidx.compose.ui:ui-test-junit4:1.7.6",
+      mvn"com.google.dagger:hilt-android-testing:2.56"
     )
   }
 
   // TODO support instrumented tests on Hilt setups
   object androidTest extends AndroidAppKotlinInstrumentedTests
-      with AndroidTestModule.AndroidJUnit {}
+      with AndroidTestModule.AndroidJUnit with AndroidHiltSupport {
+    override def kspVersion = Versions.kspVersion
+
+  }
+
+}
+
+object `shared-test` extends AndroidKotlinModule with AndroidHiltSupport {
+
+  def moduleDeps = Seq(app)
+
+  def kotlinVersion = Versions.kotlinVersion
+  def kotlinLanguageVersion = Versions.kotlinLanguageVersion
+  def kspVersion = Versions.kspVersion
+  def androidIsDebug = true
+
+  def androidSdkModule = mill.define.ModuleRef(androidSdkModule0)
+  def androidCompileSdk = Versions.androidCompileSdk
+  def androidMinSdk = Versions.androidMinSdk
+
+  def androidEnableCompose = true
+
+  def androidNamespace = "com.example.android.architecture.blueprints.todoapp.shared.test"
+
+  def kotlinSymbolProcessors: T[Seq[Dep]] = Seq(
+    mvn"androidx.room:room-compiler:2.6.1",
+    mvn"com.google.dagger:hilt-android-compiler:2.56"
+  )
 
+  def mvnDeps = super.mvnDeps() ++ Seq(
+    mvn"junit:junit:4.13.2",
+    mvn"androidx.arch.core:core-testing:2.2.0",
+    mvn"org.jetbrains.kotlinx:kotlinx-coroutines-android:1.9.0",
+    mvn"org.jetbrains.kotlinx:kotlinx-coroutines-test:1.9.0",
+    mvn"androidx.test:core-ktx:1.6.1",
+    mvn"androidx.test.ext:junit-ktx:1.2.1",
+    mvn"androidx.test:rules:1.6.1",
+    mvn"com.google.dagger:hilt-android:2.56",
+    mvn"com.google.dagger:hilt-android-testing:2.56",
+    mvn"androidx.room:room-runtime:2.6.1",
+    mvn"androidx.room:room-ktx:2.6.1"
+  )
 }
 
 /** Usage
 
 > ./mill app.androidApk
 
+> ./mill app.test
+
+> cat out/app/test/testForked.dest/test-report.xml
+<?xml version='1.0' encoding='UTF-8'?>
+<testsuites tests="46" failures="0" errors="0" skipped="0" time="...">
+...
+
 > ./mill show app.createAndroidVirtualDevice
 ...Name: test, DeviceId: medium_phone...
 

libs/androidlib/hilt/src/mill/androidlib/hilt/AndroidHiltTransformAsm.scala

@@ -25,7 +25,14 @@ object AndroidHiltTransformAsm {
 
     val destination = os.Path(args.last)
 
-    transformAsm(scanDirectory, os.walk(scanDirectory).filter(_.ext == "class"), destination)
+    val allCompiledFiles = os.walk(scanDirectory).filter(os.isFile)
+
+    transformAsm(scanDirectory, allCompiledFiles.filter(_.ext == "class"), destination)
+
+    allCompiledFiles.filterNot(_.ext == "class").foreach { file =>
+      val destinationFile = destination / file.relativeTo(scanDirectory)
+      os.copy(file, destinationFile, createFolders = true)
+    }
 
   }
 
@@ -41,7 +48,6 @@ object AndroidHiltTransformAsm {
         val destination = destinationDir / path.relativeTo(baseDir)
         transform(path, destination)
     }
-
   }
 
   private def transform(`class`: os.Path, destination: os.Path): os.Path = {

libs/androidlib/src/mill/androidlib/AndroidAppKotlinModule.scala

@@ -26,25 +26,34 @@ import upickle.implicits.namedTuples.default.given
 @mill.api.experimental
 trait AndroidAppKotlinModule extends AndroidKotlinModule with AndroidAppModule { outer =>
 
-  def kotlinSources = Task.Sources("src/main/kotlin")
+  private def kotlinSources = Task.Sources("src/main/kotlin")
   override def sources: T[Seq[PathRef]] =
     super[AndroidAppModule].sources() ++ kotlinSources()
 
-  trait AndroidAppKotlinTests extends KotlinTests with AndroidAppTests {
-    def kotlinSources = Task.Sources("src/test/kotlin")
+  trait AndroidAppKotlinTests extends AndroidAppKotlinModule with AndroidAppTests {
+    override def kotlinVersion: T[String] = outer.kotlinVersion
+
+    private def kotlinSources = Task.Sources("src/test/kotlin")
+
     override def sources: T[Seq[PathRef]] =
       super[AndroidAppTests].sources() ++ kotlinSources()
+
+    override def kotlincPluginMvnDeps: T[Seq[Dep]] = outer.kotlincPluginMvnDeps()
   }
 
   trait AndroidAppKotlinInstrumentedTests extends AndroidAppKotlinModule
       with AndroidAppInstrumentedTests {
 
-    override final def kotlinVersion = outer.kotlinVersion
-    override final def androidSdkModule = outer.androidSdkModule
+    override final def kotlinVersion: T[String] = outer.kotlinVersion
+    override final def androidSdkModule: ModuleRef[AndroidSdkModule] = outer.androidSdkModule
+
+    private def kotlinSources = Task.Sources("src/androidTest/kotlin")
+
+    override def kotlincPluginMvnDeps: T[Seq[Dep]] = outer.kotlincPluginMvnDeps()
 
-    def kotlinSources = Task.Sources("src/androidTest/kotlin")
     override def sources: T[Seq[PathRef]] =
       super[AndroidAppInstrumentedTests].sources() ++ kotlinSources()
+
   }
 
   trait AndroidAppKotlinScreenshotTests extends AndroidAppKotlinModule with TestModule with Junit5 {

libs/androidlib/src/mill/androidlib/AndroidAppModule.scala

@@ -71,7 +71,7 @@ trait AndroidAppModule extends AndroidModule { outer =>
    * In the case of android apps this the [[androidApplicationNamespace]].
    * @return
    */
-  protected override def androidGeneratedResourcesPackage: String = androidApplicationNamespace
+  override final def androidNamespace: String = androidApplicationNamespace
 
   /**
    * Android Application Id which is typically package.main .
@@ -97,7 +97,7 @@ trait AndroidAppModule extends AndroidModule { outer =>
     val manifestElem = XML.loadFile(manifestFromSourcePath.toString())
     // add the application package
     val manifestWithPackage =
-      manifestElem % Attribute(None, "package", Text(androidApplicationId), Null)
+      manifestElem % Attribute(None, "package", Text(androidApplicationNamespace), Null)
 
     val manifestWithUsesSdk = manifestWithPackage.copy(
       child = androidManifestUsesSdkSection() ++ manifestWithPackage.child
@@ -1059,7 +1059,7 @@ trait AndroidAppModule extends AndroidModule { outer =>
 
     override def androidApplicationId: String = outer.androidApplicationId
 
-    override def androidApplicationNamespace: String = outer.androidApplicationNamespace
+    override def androidApplicationNamespace: String = s"${outer.androidApplicationNamespace}.test"
 
     override def moduleDir: Path = outer.moduleDir
 
@@ -1086,8 +1086,8 @@ trait AndroidAppModule extends AndroidModule { outer =>
 
     override def resolutionParams: Task[ResolutionParams] = Task.Anon(outer.resolutionParams())
 
-    override def androidApplicationId: String = s"${outer.androidApplicationId}.test"
-    override def androidApplicationNamespace: String = outer.androidApplicationNamespace
+    override def androidApplicationId: String = s"${outer.androidApplicationId}"
+    override def androidApplicationNamespace: String = s"${outer.androidApplicationNamespace}.test"
 
     override def androidReleaseKeyAlias: T[Option[String]] = outer.androidReleaseKeyAlias()
     override def androidReleaseKeyName: Option[String] = outer.androidReleaseKeyName
@@ -1105,7 +1105,7 @@ trait AndroidAppModule extends AndroidModule { outer =>
 
     private def androidInstrumentedTestsBaseManifest: Task[Elem] = Task.Anon {
       <manifest xmlns:android="http://schemas.android.com/apk/res/android" package={
-        androidApplicationId
+        androidApplicationNamespace
       }>
         {androidManifestUsesSdkSection()}
       </manifest>
@@ -1122,7 +1122,7 @@ trait AndroidAppModule extends AndroidModule { outer =>
       val manifestWithInstrumentation = {
         val instrumentation =
           <instrumentation android:name={testFrameworkName} android:targetPackage={
-            androidApplicationNamespace
+            outer.androidApplicationNamespace
           }/>
         baseManifestElem.copy(child = baseManifestElem.child ++ instrumentation)
       }
@@ -1181,7 +1181,7 @@ trait AndroidAppModule extends AndroidModule { outer =>
           "instrument",
           "-w",
           "-r",
-          s"${androidApplicationId}/${testFramework()}"
+          s"${androidApplicationNamespace}/${testFramework()}"
         )
       ).spawn()
 

libs/androidlib/src/mill/androidlib/AndroidKotlinModule.scala

@@ -6,7 +6,7 @@ import mill.{T, Task}
 
 // TODO expose Compose configuration options
 // https://kotlinlang.org/docs/compose-compiler-options.html possible options
-trait AndroidKotlinModule extends KotlinModule {
+trait AndroidKotlinModule extends KotlinModule with AndroidModule {
 
   /**
    * Enable Jetpack Compose support in the module. Default is `false`.
@@ -24,10 +24,36 @@ trait AndroidKotlinModule extends KotlinModule {
         // Compose compiler version -> Kotlin version
         Task.fail("Compose can be used only with Kotlin version 2 or newer.")
       } else {
-        deps ++ Seq(
-          mvn"org.jetbrains.kotlin:kotlin-compose-compiler-plugin:${kotlinVersion()}"
-        )
+        if (kotlinUseEmbeddableCompiler())
+          deps ++ Seq(
+            mvn"org.jetbrains.kotlin:kotlin-compose-compiler-plugin-embeddable:${kotlinVersion()}"
+          )
+        else
+          deps ++ Seq(
+            mvn"org.jetbrains.kotlin:kotlin-compose-compiler-plugin:${kotlinVersion()}"
+          )
       }
     } else deps
   }
+
+  /**
+   * If this module has any module dependencies, we need to tell the kotlin compiler to
+   * handle the compiled output as a friend path so top level declarations are visible.
+   */
+  def kotlincFriendPaths: T[Option[String]] = Task {
+    val compiledCodePaths = Task.traverse(transitiveModuleCompileModuleDeps)(m =>
+      Task.Anon {
+        Seq(m.compile().classes.path)
+      }
+    )().flatten
+
+    val friendlyPathFlag: Option[String] =
+      compiledCodePaths.headOption.map(_ => s"-Xfriend-paths=${compiledCodePaths.mkString(",")}")
+
+    friendlyPathFlag
+  }
+
+  override def kotlincOptions: T[Seq[String]] = Task {
+    super.kotlincOptions() ++ kotlincFriendPaths().toSeq
+  }
 }

libs/androidlib/src/mill/androidlib/AndroidLibModule.scala

@@ -18,7 +18,7 @@ trait AndroidLibModule extends AndroidModule with PublishModule {
    */
   def androidLibPackage: String
 
-  override protected def androidGeneratedResourcesPackage: String = androidLibPackage
+  override final def androidNamespace: String = androidLibPackage
 
   /**
    * Provides os.Path to an XML file containing configuration and metadata about your android application.

libs/androidlib/src/mill/androidlib/AndroidModule.scala

@@ -10,7 +10,7 @@ import mill.util.Jvm
 import upickle.implicits.namedTuples.default.given
 
 import scala.collection.immutable
-import scala.xml.XML
+import scala.xml.*
 
 trait AndroidModule extends JavaModule {
 
@@ -47,10 +47,34 @@ trait AndroidModule extends JavaModule {
    */
   def androidSdkModule: ModuleRef[AndroidSdkModule]
 
+  private def androidManifestUsesSdkSection: Task[Elem] = Task.Anon {
+    val minSdkVersion = androidMinSdk().toString
+    val targetSdkVersion = androidTargetSdk().toString
+    <uses-sdk android:minSdkVersion={minSdkVersion} />
+  }
+
   /**
-   * Provides os.Path to an XML file containing configuration and metadata about your android library.
+   * Provides os.Path to an XML file containing configuration and metadata about your android application.
+   * TODO dynamically add android:debuggable
    */
-  def androidManifest: Task[PathRef] = Task.Source("src/main/AndroidManifest.xml")
+  def androidManifest: T[PathRef] = Task {
+    val manifestFromSourcePath = moduleDir / "src/main/AndroidManifest.xml"
+
+    val manifestElem = XML.loadFile(manifestFromSourcePath.toString()) %
+      Attribute(None, "xmlns:android", Text("http://schemas.android.com/apk/res/android"), Null)
+    // add the application package
+    val manifestWithPackage =
+      manifestElem % Attribute(None, "package", Text(androidNamespace), Null)
+
+    val manifestWithUsesSdk = manifestWithPackage.copy(
+      child = androidManifestUsesSdkSection() ++ manifestWithPackage.child
+    )
+
+    val generatedManifestPath = Task.dest / "AndroidManifest.xml"
+    os.write(generatedManifestPath, manifestWithUsesSdk.mkString)
+
+    PathRef(generatedManifestPath)
+  }
 
   /**
    * Controls debug vs release build type. Default is `true`, meaning debug build will be generated.
@@ -360,8 +384,11 @@ trait AndroidModule extends JavaModule {
     libClasses :+ PathRef(mainRClassPath)
   }
 
-  /** In which package to place the generated R sources */
-  protected def androidGeneratedResourcesPackage: String
+  /**
+   * Namespace of the Android module.
+   * Used in manifest package and also used as the package to place the generated R sources
+   */
+  def androidNamespace: String
 
   /**
    * Compiles Android resources and generates `R.java` and `res.apk`.
@@ -443,7 +470,7 @@ trait AndroidModule extends JavaModule {
       "--manifest",
       androidMergedManifest().path.toString,
       "--custom-package",
-      androidGeneratedResourcesPackage,
+      androidNamespace,
       "--java",
       rClassDir.toString,
       "--min-sdk-version",