Android: Test apk size reduction (#5963)

For #5961

## Implementation

- Add the outer AndroidAppModule in the compileModuleDeps instead of
moduleDeps
- Fix some packaging mappings to use run resolved deps
- Fix the compile only classpath to pass the compileModuleDeps
classpaths too
- By having instrumented tests inherit the
`androidDefaultProguardFileNames` from the parent module, the android
tests are working. It's not clear to me why, I found it due to some
trial and error. To achieve this kind of inheritance without major
rewiring I've moved the method to `AndroidAppModule`

## Other fixes and cleanups
- Somehow androidtodo had a wrong namespace, maybe a find and replace
mishap
- Removed an unnecessary dep from androidtodo test module

## Outcome

This avoids packaging the main (app) module dependencies and source code
into the test apk.

## Result (Jetsnack)

<img width="1853" height="1076" alt="image"
src="https://github.com/user-attachments/assets/daba647b-8632-4ef2-b399-bc6fd14e6be6"
/>

## Future work

I had some difficulties reaching this point and I think the 13MB
reduction is very satisfiable at this stage. In the gradle's case, it
appears some classes are erased by R8 but I haven't pinpointed exactly
how it does it.

Author: vaslabs

example/thirdparty/androidtodo/build.mill

@@ -133,7 +133,6 @@ object app
     def mvnDeps = super.mvnDeps() ++ composeDeps ++ 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.navigation:navigation-testing:2.8.5",
       mvn"androidx.test.espresso:espresso-core:3.6.1",
@@ -185,7 +184,6 @@ object app
       // Dependencies for Android unit tests
       mvn"junit:junit:4.13.2",
       mvn"org.jetbrains.kotlinx:kotlinx-coroutines-test:1.9.0",
-      mvn"org.jetbrains.kotlinx:kotlinx-coroutines-android:1.9.0",
       // AndroidX Test - Instrumented testing
       mvn"androidx.test:core-ktx:1.6.1",
       mvn"androidx.test.ext:junit-ktx:1.2.1",
@@ -227,7 +225,7 @@ object `shared-test` extends AndroidKotlinModule, AndroidHiltSupport {
 
   def androidEnableCompose = true
 
-  def androidNamespace = "com.example.android.architecture.blueprints.todoapp.daemon.test"
+  def androidNamespace = "com.example.android.architecture.blueprints.todoapp.shared.test"
 
   def kotlinSymbolProcessors: T[Seq[Dep]] = Seq(
     mvn"androidx.room:room-compiler:2.7.1",
@@ -237,7 +235,6 @@ object `shared-test` extends AndroidKotlinModule, AndroidHiltSupport {
   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",

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

@@ -822,7 +822,7 @@ trait AndroidAppModule extends AndroidModule { outer =>
 
   }
 
-  def knownProguardRules: T[String] = Task {
+  def androidKnownProguardRules: T[String] = Task {
     // TODO need also pick proguard files from
     // [[moduleDeps]]
     androidUnpackArchives()
@@ -833,15 +833,13 @@ trait AndroidAppModule extends AndroidModule { outer =>
       .mkString("\n")
   }
 
-  override def androidProguard: T[PathRef] = Task {
-    val inheritedProguardFile = super.androidProguard()
-    val proguardFile = Task.dest / "proguard-rules.pro"
-
-    os.write(proguardFile, os.read(inheritedProguardFile.path))
-
-    os.write.append(proguardFile, knownProguardRules())
-
-    PathRef(proguardFile)
+  /**
+   * File names that are provided by the Android SDK in `androidSdkModule().androidProguardPath().path`
+   *
+   * For now, it's only used by [[AndroidR8AppModule]]
+   */
+  def androidDefaultProguardFileNames: Task[Seq[String]] = Task.Anon {
+    Seq.empty[String]
   }
 
   // uses the d8 tool to generate the dex file, when minification is disabled
@@ -896,6 +894,9 @@ trait AndroidAppModule extends AndroidModule { outer =>
 
     override def androidIsDebug: T[Boolean] = Task { true }
 
+    override def moduleDeps: Seq[JavaModule] = Seq.empty
+    override def compileModuleDeps: Seq[JavaModule] = Seq(outer)
+
     override def resolutionParams: Task[ResolutionParams] = Task.Anon(outer.resolutionParams())
 
     override def androidApplicationId: String = s"${outer.androidApplicationId}.test"
@@ -913,6 +914,10 @@ trait AndroidAppModule extends AndroidModule { outer =>
 
     def androidResources: T[Seq[PathRef]] = Task.Sources("src/androidTest/res")
 
+    override def androidDefaultProguardFileNames: Task[Seq[String]] = Task.Anon {
+      outer.androidDefaultProguardFileNames()
+    }
+
     override def testFramework: T[String] = Task {
       "androidx.test.runner.AndroidJUnitRunner"
     }
@@ -1063,15 +1068,15 @@ trait AndroidAppModule extends AndroidModule { outer =>
      * as its apk is installed separately
      */
     def androidTransitiveTestClasspath: T[Seq[PathRef]] = Task {
-      Task.traverse(transitiveModuleCompileModuleDeps) {
+      Task.traverse(transitiveRunModuleDeps) {
         m =>
           Task.Anon(m.localRunClasspath())
       }().flatten
     }
 
     /** The instrumented dex should just contain the test dependencies and locally tested files */
     override def androidPackagedClassfiles: T[Seq[PathRef]] = Task {
-      (testClasspath() ++ androidTransitiveTestClasspath())
+      androidTransitiveTestClasspath()
         .map(_.path).filter(os.isDir)
         .flatMap(os.walk(_))
         .filter(os.isFile)
@@ -1080,7 +1085,7 @@ trait AndroidAppModule extends AndroidModule { outer =>
     }
 
     override def androidPackagedDeps: T[Seq[PathRef]] = Task {
-      androidResolvedMvnDeps()
+      androidResolvedRunMvnDeps()
     }
 
     /**

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

@@ -193,11 +193,11 @@ trait AndroidModule extends JavaModule { outer =>
 
   /**
    * Gets all the compiled Android resources (typically in res/ directory)
-   * from the [[transitiveModuleCompileModuleDeps]]
+   * from the [[transitiveModuleRunModuleDeps]]
    * @return a sequence of PathRef to the compiled resources
    */
   def androidTransitiveCompiledResources: T[Seq[PathRef]] = Task {
-    Task.traverse(transitiveModuleCompileModuleDeps) {
+    Task.traverse(transitiveModuleRunModuleDeps) {
       case m: AndroidModule =>
         Task.Anon(m.androidCompiledModuleResources())
       case _ =>
@@ -264,7 +264,7 @@ trait AndroidModule extends JavaModule { outer =>
   override def compileClasspath: T[Seq[PathRef]] = Task {
     // TODO process metadata shipped with Android libs. It can have some rules with Target SDK, for example.
     // TODO support baseline profiles shipped with Android libs.
-    androidDepsClasspath() ++ androidTransitiveLibRClasspath()
+    androidDepsClasspath() ++ androidTransitiveLibRClasspath() ++ androidTransitiveModuleRClasspath()
   }
 
   /**
@@ -522,6 +522,24 @@ trait AndroidModule extends JavaModule { outer =>
     }().flatten
   }
 
+  def androidTransitiveModuleRClasspath: T[Seq[PathRef]] = Task {
+    Task.traverse(compileModuleDepsChecked) {
+      case m: AndroidModule =>
+        Task.Anon(Seq(m.androidProcessedResources()))
+      case _ =>
+        Task.Anon(Seq.empty[PathRef])
+    }().flatten
+  }
+
+  def androidTransitiveCompileOnlyClasspath: T[Seq[PathRef]] = Task {
+    Task.traverse(compileModuleDepsChecked) {
+      case m: AndroidModule =>
+        Task.Anon(Seq(m.compile().classes))
+      case _ =>
+        Task.Anon(Seq.empty[PathRef])
+    }().flatten
+  }
+
   /**
    * Namespace of the Android module.
    * Used in manifest package and also used as the package to place the generated R sources

libs/androidlib/src/mill/androidlib/AndroidR8AppModule.scala

@@ -54,7 +54,7 @@ trait AndroidR8AppModule extends AndroidAppModule {
   }
 
   def androidLibraryProguardConfigs: Task[Seq[PathRef]] = Task {
-    androidUnpackArchives()
+    androidUnpackRunArchives()
       // TODO need also collect rules from other modules,
       // but Android lib module doesn't yet exist
       .flatMap(_.proguardRules)
@@ -71,6 +71,27 @@ trait AndroidR8AppModule extends AndroidAppModule {
     androidDefaultProguardFiles() ++ androidProjectProguardFiles() ++ androidLibraryProguardConfigs()
   }
 
+  /**
+   * Creates a file for letting know R8 that [[compileModuleDeps]] and
+   * [[compileMvnDeps]] are in compile classpath only and not packaged with the apps.
+   * Useful for dependencies that are provided in devices and compile only module deps
+   * such as for avoiding to package main sources in the androidTest apk.
+   */
+  def androidR8CompileOnlyClasspath: T[Option[PathRef]] = Task {
+    val resolvedCompileMvnDeps =
+      androidResolvedCompileMvnDeps() ++ androidTransitiveCompileOnlyClasspath() ++ androidTransitiveModuleRClasspath()
+    if (!resolvedCompileMvnDeps.isEmpty) {
+      val compiledMvnDepsFile = Task.dest / "compile-only-classpath.txt"
+      os.write.over(
+        compiledMvnDepsFile,
+        resolvedCompileMvnDeps.map(_.path.toString()).mkString("\n")
+      )
+      Some(PathRef(compiledMvnDepsFile))
+    } else
+      None
+
+  }
+
   /** Concatenates all rules into one file */
   override def androidProguard: T[PathRef] = Task {
     val inheritedProguardFile = super.androidProguard()
@@ -98,14 +119,6 @@ trait AndroidR8AppModule extends AndroidAppModule {
     )
   }
 
-  /**
-   * File names that are provided by the Android SDK in `androidSdkModule().androidProguardPath().path`
-   * @return
-   */
-  def androidDefaultProguardFileNames: Task[Seq[String]] = Task.Anon {
-    Seq.empty[String]
-  }
-
   private def androidDefaultProguardFiles: Task[Seq[PathRef]] = Task.Anon {
     val dest = Task.dest
     androidDefaultProguardFileNames().map { fileName =>
@@ -242,18 +255,14 @@ trait AndroidR8AppModule extends AndroidAppModule {
 
     r8ArgsBuilder ++= pgArgs
 
-    val resolvedCompileMvnDeps = androidResolvedCompileMvnDeps()
-    if (!resolvedCompileMvnDeps.isEmpty) {
-      val compiledMvnDepsFile = Task.dest / "compiled-mvndeps.txt"
-      os.write.over(
-        compiledMvnDepsFile,
-        androidResolvedCompileMvnDeps().map(_.path.toString()).mkString("\n")
-      )
-      r8ArgsBuilder ++= Seq(
+    val compileOnlyClasspath = androidR8CompileOnlyClasspath()
+
+    r8ArgsBuilder ++= compileOnlyClasspath.toSeq.flatMap(compiledMvnDepsFile =>
+      Seq(
         "--classpath",
-        "@" + compiledMvnDepsFile.toString
+        "@" + compiledMvnDepsFile.path.toString
       )
-    }
+    )
 
     r8ArgsBuilder ++= androidR8Args()