Use R8 optimization tool in Android modules (#4892)

irodotos7 · web-flow · commit 9af87fe512ab · 2025-04-23T08:35:02.000-07:00
A step back from this PR #4743 I created a smaller, clear PR with the R8 task only and without the separation of Debug and Release Install paths ## Motivation As part of Mill’s Android integration, we want to use the R8 optimization tool to create smaller dex files ![image](https://github.com/user-attachments/assets/9afaf36a-b986-4fc6-9397-2f906ff8fb66) ![image](https://github.com/user-attachments/assets/a6072464-4547-43b0-8946-9b82de70ff6f) ## Provided in this PR 1) Run the R8 task which will shrink the dex files according to the proguard rules
diff --git a/example/androidlib/java/1-hello-world/build.mill b/example/androidlib/java/1-hello-world/build.mill
@@ -24,7 +24,12 @@ object app extends AndroidAppModule {
   def androidApplicationId = "com.helloworld.app"
   def androidApplicationNamespace = "com.helloworld.app"
 
-  // Configuration for ReleaseKey
+  /**
+   * Configuration for ReleaseKey
+   * WARNING: Replace these default values with secure and private credentials before using in production.
+   * Never use these defaults in a production environment as they are not secure.
+   * This is just for testing purposes.
+   */
   def androidReleaseKeyName: T[Option[String]] = Task { Some("releaseKey.jks") }
   def androidReleaseKeyAlias: T[Option[String]] = Task { Some("releaseKey") }
   def androidReleaseKeyPass: T[Option[String]] = Task { Some("MillBuildTool") }
diff --git a/example/androidlib/java/2-app-bundle/build.mill b/example/androidlib/java/2-app-bundle/build.mill
@@ -17,6 +17,12 @@ object bundle extends AndroidAppBundle {
   def androidSdkModule = mill.define.ModuleRef(androidSdkModule0)
   def androidCompileSdk = 35
 
+  /**
+   * Configuration for ReleaseKey
+   * WARNING: Replace these default values with secure and private credentials before using in production.
+   * Never use these defaults in a production environment as they are not secure.
+   * This is just for testing purposes.
+   */
   def androidApplicationId = "com.helloworld.app"
   def androidApplicationNamespace = "com.helloworld.app"
 
diff --git a/example/androidlib/java/4-sum-lib-java/build.mill b/example/androidlib/java/4-sum-lib-java/build.mill
@@ -38,7 +38,12 @@ object lib extends AndroidLibModule with PublishModule {
     developers = Seq(Developer("lihaoyi", "Li Haoyi", "https://github.com/lihaoyi"))
   )
 
-  // Configuration for ReleaseKey
+  /**
+   * Configuration for ReleaseKey
+   * WARNING: Replace these default values with secure and private credentials before using in production.
+   * Never use these defaults in a production environment as they are not secure.
+   * This is just for testing purposes.
+   */
   def androidReleaseKeyAlias: T[Option[String]] = Task { Some("releaseKey") }
   def androidReleaseKeyPass: T[Option[String]] = Task { Some("MillBuildTool") }
   def androidReleaseKeyStorePass: T[Option[String]] = Task { Some("MillBuildTool") }
diff --git a/example/androidlib/java/5-R8/app/proguard-rules.pro b/example/androidlib/java/5-R8/app/proguard-rules.pro
@@ -0,0 +1,23 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# override def proguardConfigs: T[Seq[PathRef]] in build.mill
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+-renamesourcefileattribute SourceFilex
+
+-keep class com.helloworld.** { *; }
diff --git a/example/androidlib/java/5-R8/app/releaseKey.jks b/example/androidlib/java/5-R8/app/releaseKey.jks
diff --git a/example/androidlib/java/5-R8/app/src/androidTest/java/com/helloworld/app/ExampleInstrumentedTest.java b/example/androidlib/java/5-R8/app/src/androidTest/java/com/helloworld/app/ExampleInstrumentedTest.java
@@ -0,0 +1,26 @@
+package com.helloworld.app;
+
+import static org.junit.Assert.*;
+
+import android.content.Context;
+import androidx.test.ext.junit.runners.AndroidJUnit4;
+import androidx.test.platform.app.InstrumentationRegistry;
+import com.helloworld.SampleLogic;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/**
+ * Instrumented test, which will execute on an Android device.
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+@RunWith(AndroidJUnit4.class)
+public class ExampleInstrumentedTest {
+  @Test
+  public void useAppContext() {
+    // Context of the app under test.
+    Context appContext = InstrumentationRegistry.getInstrumentation().getTargetContext();
+    assertEquals("com.helloworld.app", appContext.getPackageName());
+    assertEquals(32.0f, SampleLogic.textSize(), 0.0001f);
+  }
+}
diff --git a/example/androidlib/java/5-R8/app/src/main/AndroidManifest.xml b/example/androidlib/java/5-R8/app/src/main/AndroidManifest.xml
@@ -0,0 +1,15 @@
+<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="com.helloworld.app" android:versionCode="1" android:versionName="1.0">
+    <uses-sdk android:minSdkVersion="9" android:targetSdkVersion="35"/>
+    <application android:label="@string/app_name" android:theme="@android:style/Theme.Light.NoTitleBar" android:debuggable="true">
+        <activity android:name=".MainActivity"
+                android:exported="true">
+            <intent-filter>
+                <action android:name="android.intent.action.MAIN"/>
+                <category android:name="android.intent.category.LAUNCHER"/>
+            </intent-filter>
+        </activity>
+    </application>
+    <instrumentation
+            android:name="androidx.test.runner.AndroidJUnitRunner"
+            android:targetPackage="com.helloworld.app" />
+</manifest>
diff --git a/example/androidlib/java/5-R8/app/src/main/java/com/helloworld/SampleLogic.java b/example/androidlib/java/5-R8/app/src/main/java/com/helloworld/SampleLogic.java
@@ -0,0 +1,8 @@
+package com.helloworld;
+
+public class SampleLogic {
+
+  public static float textSize() {
+    return 32f;
+  }
+}
diff --git a/example/androidlib/java/5-R8/app/src/main/java/com/helloworld/app/MainActivity.java b/example/androidlib/java/5-R8/app/src/main/java/com/helloworld/app/MainActivity.java
@@ -0,0 +1,39 @@
+package com.helloworld.app;
+
+import android.app.Activity;
+import android.os.Bundle;
+import android.view.Gravity;
+import android.view.ViewGroup.LayoutParams;
+import android.widget.TextView;
+
+public class MainActivity extends Activity {
+  @Override
+  protected void onCreate(Bundle savedInstanceState) {
+    super.onCreate(savedInstanceState);
+
+    // Create a new TextView
+    TextView textView = new TextView(this);
+
+    // Set the text to the string resource
+    textView.setText(getString(R.string.hello_world));
+
+    // Set text size
+    textView.setTextSize(32);
+
+    // Center the text within the view
+    textView.setGravity(Gravity.CENTER);
+
+    // Set the layout parameters (width and height)
+    textView.setLayoutParams(
+        new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT));
+
+    // Set the text color using a resource
+    textView.setTextColor(getResources().getColor(R.color.text_green));
+
+    // Set the background color using a resource
+    textView.setBackgroundColor(getResources().getColor(R.color.white));
+
+    // Set the content view to display the TextView
+    setContentView(textView);
+  }
+}
diff --git a/example/androidlib/java/5-R8/app/src/main/res/values/colors.xml b/example/androidlib/java/5-R8/app/src/main/res/values/colors.xml
@@ -0,0 +1,4 @@
+<resources>
+    <color name="white">#FFFFFF</color>
+    <color name="text_green">#34A853</color>
+</resources>
diff --git a/example/androidlib/java/5-R8/app/src/main/res/values/strings.xml b/example/androidlib/java/5-R8/app/src/main/res/values/strings.xml
@@ -0,0 +1,4 @@
+<resources>
+    <string name="app_name">HelloWorldApp</string>
+    <string name="hello_world">Hello, World Java!</string>
+</resources>
diff --git a/example/androidlib/java/5-R8/app/src/test/java/com/helloworld/ExampleUnitTest.java b/example/androidlib/java/5-R8/app/src/test/java/com/helloworld/ExampleUnitTest.java
@@ -0,0 +1,20 @@
+package com.helloworld;
+
+import static org.junit.Assert.*;
+
+import com.helloworld.app.R;
+import org.junit.Test;
+
+/**
+ * Example local unit test, which will execute on the development machine (host).
+ *
+ * @see <a href="http://d.android.com/tools/testing">Testing documentation</a>
+ */
+public class ExampleUnitTest {
+  @Test
+  public void textSize_isCorrect() {
+
+    assertEquals(32f, SampleLogic.textSize(), 0.000001f);
+    assertEquals(0x7f010000, R.color.text_green);
+  }
+}
diff --git a/example/androidlib/java/5-R8/app/test-proguard-rules.pro b/example/androidlib/java/5-R8/app/test-proguard-rules.pro
@@ -0,0 +1,24 @@
+# Proguard rules for instrumented tests
+
+# Suppress warnings (so that you aren’t spammed with messages for unused rules)
+-ignorewarnings
+
+# Do not run any code optimizations – we want to keep our test code unchanged.
+-dontoptimize
+
+# Keep all annotation metadata (needed for reflection-based test frameworks)
+-keepattributes *Annotation*
+
+# Keep all Espresso framework classes and specifically ensure that the idling resources aren’t stripped
+-keep class androidx.test.espresso.** { *; }
+-keep class androidx.test.espresso.IdlingRegistry { *; }
+-keep class androidx.test.espresso.IdlingResource { *; }
+
+# Suppress notes and warnings for older JUnit and Android test classes
+-dontnote junit.framework.**
+-dontnote junit.runner.**
+
+-dontwarn androidx.test.**
+-dontwarn org.junit.**
+-dontwarn org.hamcrest.**
+-dontwarn com.squareup.javawriter.JavaWriter
diff --git a/example/androidlib/java/5-R8/build.mill b/example/androidlib/java/5-R8/build.mill
@@ -0,0 +1,104 @@
+// R8 is a code shrinker and obfuscator for Android applications. Is designed to optimize the size of the APK
+// while maintaining the functionality of the app.
+// When using R8, you can configure the rules for code shrinking and obfuscation in a ProGuard configuration file.
+// R8 relies on ProGuard rules files to adjust its default behavior and gain a better understanding of your app’s structure,
+// such as identifying the classes that act as entry points. While you can modify some of these rules files,
+// certain rules may be automatically generated by compile-time tools (like AAPT2) or inherited from your app’s library dependencies.
+// You need 2 files on the root of your project:
+//
+// * proguard-rules.pro: This file contains the rules for R8 to follow when shrinking and obfuscating the code.
+//
+// * test-proguard-rules.pro: This file contains the rules for R8 to follow when shrinking and obfuscating the unit and instrumented tests.
+//
+// You can also override the default Proguard files by using `override def proguardConfigs: T[Seq[PathRef]]`
+// More informations about the R8 in general and about the Proguard rules files can be found in the links below:
+//
+// https://developer.android.com/build/shrink-code
+//
+// https://www.guardsquare.com/manual/configuration/usage
+package build
+
+import mill._, androidlib._, scalalib._
+
+object androidSdkModule0 extends AndroidSdkModule { // <1>
+  def buildToolsVersion = "35.0.0"
+}
+
+object app extends AndroidAppModule { // <2>
+  def androidSdkModule = mill.define.ModuleRef(androidSdkModule0)
+  def androidMinSdk = 19
+  def androidCompileSdk = 35
+  def androidApplicationId = "com.helloworld.app"
+  def androidApplicationNamespace = "com.helloworld.app"
+
+  /**
+   * Configuration for ReleaseKey
+   * WARNING: Replace these default values with secure and private credentials before using in production.
+   * Never use these defaults in a production environment as they are not secure.
+   * This is just for testing purposes.
+   */
+  def androidReleaseKeyName: T[Option[String]] = Task { Some("releaseKey.jks") }
+  def androidReleaseKeyAlias: T[Option[String]] = Task { Some("releaseKey") }
+  def androidReleaseKeyPass: T[Option[String]] = Task { Some("MillBuildTool") }
+  def androidReleaseKeyStorePass: T[Option[String]] = Task { Some("MillBuildTool") }
+
+  override def androidVirtualDeviceIdentifier: String = "java-test"
+
+  // Unit tests for the application
+  object test extends AndroidAppTests with TestModule.Junit4 {
+    def mvnDeps = super.mvnDeps() ++ Seq(
+      mvn"junit:junit:4.13.2"
+    )
+  }
+
+  // Instrumented tests (runs on emulator)
+  object it extends AndroidAppInstrumentedTests with AndroidTestModule.AndroidJUnit {
+    def androidSdkModule = mill.define.ModuleRef(androidSdkModule0)
+    override def instrumentationPackage = "com.helloworld.app"
+
+    /* TODO currently the dependency resolution ignores the platform type and kotlinx-coroutines-core has
+     * conflicting classes with kotlinx-coroutines-core-jvm . Remove the exclusions once the dependency
+     * resolution resolves conflicts between androidJvm and jvm platform types
+     */
+    def mvnDeps = super.mvnDeps() ++ Seq(
+      mvn"androidx.test.ext:junit:1.2.1".exclude(
+        ("org.jetbrains.kotlinx", "kotlinx-coroutines-core-jvm")
+      ),
+      mvn"androidx.test:runner:1.6.2",
+      mvn"androidx.test.espresso:espresso-core:3.5.1".exclude(
+        ("org.jetbrains.kotlinx", "kotlinx-coroutines-core-jvm")
+      ),
+      mvn"junit:junit:4.13.2"
+    )
+  }
+
+}
+
+// <1> Create and configure an Android SDK module to manage Android SDK paths and tools.
+// <2> The actual Android application
+
+/** Usage
+
+> ./mill show app.androidApk
+".../out/app/androidApk.dest/app.apk"
+
+> ./mill show app.createAndroidVirtualDevice
+...Name: java-test, DeviceId: medium_phone...
+
+> ./mill show app.startAndroidEmulator
+
+> ./mill show app.androidReleaseInstall
+...All files should be loaded. Notifying the device...
+
+> ./mill show app.stopAndroidEmulator
+
+> ./mill show app.deleteAndroidVirtualDevice
+
+*/
+
+// R8 will run automatically when you run the `androidReleaseInstall` task.
+// If you want to create the APK without R8, you can use the `androidApk` task to create the not-optimized APK. You can also
+// run the `andoidInstall` task that will automaticaly run the `androidApk` and also install it in the emulator.
+// The `androidReleaseInstall` task will install the optimized APK on the emulator.
+// So first you need to create the emulator and start it.
+// After the emulator is started, you can run the `androidReleaseInstall` task and see the app in the emulator.
diff --git a/example/androidlib/kotlin/1-hello-kotlin/app/proguard-rules.pro b/example/androidlib/kotlin/1-hello-kotlin/app/proguard-rules.pro
@@ -0,0 +1,24 @@
+# Add project specific ProGuard rules here.
+# You can control the set of applied configuration files using the
+# override def proguardConfigs: T[Seq[PathRef]] in build.mill
+
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}
+
+# Uncomment this to preserve the line number information for
+# debugging stack traces.
+#-keepattributes SourceFile,LineNumberTable
+
+# If you keep the line number information, uncomment this to
+# hide the original source file name.
+-renamesourcefileattribute SourceFilex
+
+-keep class com.helloworld.** { *; }
diff --git a/example/androidlib/kotlin/1-hello-kotlin/app/test-proguard-rules.pro b/example/androidlib/kotlin/1-hello-kotlin/app/test-proguard-rules.pro
@@ -0,0 +1,24 @@
+# Proguard rules for instrumented tests
+
+# Suppress warnings (so that you aren’t spammed with messages for unused rules)
+-ignorewarnings
+
+# Do not run any code optimizations – we want to keep our test code unchanged.
+-dontoptimize
+
+# Keep all annotation metadata (needed for reflection-based test frameworks)
+-keepattributes *Annotation*
+
+# Keep all Espresso framework classes and specifically ensure that the idling resources aren’t stripped
+-keep class androidx.test.espresso.** { *; }
+-keep class androidx.test.espresso.IdlingRegistry { *; }
+-keep class androidx.test.espresso.IdlingResource { *; }
+
+# Suppress notes and warnings for older JUnit and Android test classes
+-dontnote junit.framework.**
+-dontnote junit.runner.**
+
+-dontwarn androidx.test.**
+-dontwarn org.junit.**
+-dontwarn org.hamcrest.**
+-dontwarn com.squareup.javawriter.JavaWriter
diff --git a/example/androidlib/kotlin/1-hello-kotlin/build.mill b/example/androidlib/kotlin/1-hello-kotlin/build.mill
diff --git a/example/androidlib/kotlin/4-sum-lib-kotlin/build.mill b/example/androidlib/kotlin/4-sum-lib-kotlin/build.mill
diff --git a/libs/androidlib/src/mill/androidlib/AndroidAppModule.scala b/libs/androidlib/src/mill/androidlib/AndroidAppModule.scala
diff --git a/libs/androidlib/src/mill/androidlib/AndroidModule.scala b/libs/androidlib/src/mill/androidlib/AndroidModule.scala
diff --git a/libs/androidlib/src/mill/androidlib/AndroidSdkModule.scala b/libs/androidlib/src/mill/androidlib/AndroidSdkModule.scala
diff --git a/website/docs/modules/ROOT/pages/android/java.adoc b/website/docs/modules/ROOT/pages/android/java.adoc
