[r8] Add configurable private-member obfuscation and optimization

Documentation/docs-mobile/building-apps/build-properties.md

@@ -1115,6 +1115,22 @@ r8 dex-compiler and shrinker. The default value is a path into the
 .NET for Android workload installation. For further information see our
 documentation on [D8 and R8][d8-r8].
 
+## AndroidR8ObfuscationMode
+
+An enum-style property that specifies how `r8` obfuscates Java names when
+[`$(AndroidLinkTool)`](#androidlinktool) is `r8`. Supported values are:
+
+- `private-members` preserves Java class and interface names and public or
+  protected member names. Private and package-private members can be
+  obfuscated, and R8 optimization is enabled.
+- `disabled` disables obfuscation, preserves all Java names, and uses the
+  non-optimizing Android R8 defaults.
+
+This property does not disable R8 code shrinking.
+
+This property was introduced in a .NET 10 servicing release. It defaults to
+`disabled` in .NET 10 and to `private-members` in .NET 11 and later.
+
 ## AndroidResgenExtraArgs
 
 Specifies

build-tools/installers/create-installers.targets

@@ -83,6 +83,7 @@
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)java_runtime_clr.dex" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)java_runtime_fastdev_clr.dex" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)manifestmerger.jar" />
+    <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)proguard-android-optimize.txt" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)proguard-android.txt" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)protobuf-net.dll" />
     <_MSBuildFiles Include="$(MicrosoftAndroidSdkOutDir)System.CodeDom.dll" />

src/Xamarin.Android.Build.Tasks/Resources/proguard_trimmable_nativeaot.cfg

@@ -1,11 +1,15 @@
 # Xamarin.Android NativeAOT trimmable typemap configuration.
 
--dontobfuscate
-
 -keep class net.dot.jni.** { *; <init>(...); }
+# Loaded by name from managed code.
+-keep class net.dot.android.ApplicationRegistration { *; }
 -keep class net.dot.android.crypto.** { *; <init>(...); }
 # NativeAOT resolves these interface methods through JNI during startup.
 -keep class mono.android.IGCUserPeer { *; }
+# Native hosts resolve these package-private fields by name during startup.
+-keepclassmembers class mono.android.Runtime {
+   static java.lang.Class *;
+}
 
 -keepclassmembers class * extends android.view.View {
    *** set*(...);

src/Xamarin.Android.Build.Tasks/Resources/proguard_xamarin.cfg

@@ -1,7 +1,5 @@
 # This is Xamarin-specific (and enhanced) configuration.
 
--dontobfuscate
-
 -keep class android.support.multidex.MultiDexApplication { <init>(); }
 -keep class net.dot.jni.** { *; <init>(); }
 -keep class mono.MonoRuntimeProvider* { *; <init>(...); }
@@ -22,6 +20,8 @@
 -keepclassmembers class md52ce486a14f4bcd95899665e9d932190b.** { *; <init>(...); }
 
 # .NET runtime
+# Loaded by name from managed code.
+-keep class net.dot.android.ApplicationRegistration { *; }
 -keep class net.dot.android.crypto.** { *; <init>(...); }
 
 # Android's template misses fluent setters...

src/Xamarin.Android.Build.Tasks/Tasks/R8.cs

@@ -37,6 +37,7 @@ public class R8 : D8
 		public string? BuildMetadataFileOutput { get; set; }
 		public ITaskItem []? ProguardConfigurationFiles { get; set; }
 		public bool UseTrimmableNativeAotProguardConfiguration { get; set; }
+		public string ObfuscationMode { get; set; } = "private-members";
 
 		// User-authored AndroidJavaSource (Bind != true) .java files. These have no managed peer and are
 		// therefore absent from the acw-map, so they must be kept explicitly when shrinking is enabled.
@@ -191,6 +192,9 @@ protected override string CreateResponseFile ()
 				}
 				if (!ProguardCommonXamarinConfiguration.IsNullOrWhiteSpace ()) {
 					using (var xamcfg = File.CreateText (ProguardCommonXamarinConfiguration)) {
+						WriteObfuscationRules (xamcfg, ObfuscationMode);
+						xamcfg.WriteLine ();
+						xamcfg.Flush ();
 						if (UseTrimmableNativeAotProguardConfiguration) {
 							using var stream = GetEmbeddedResourceStream ("proguard_trimmable_nativeaot.cfg");
 							stream.CopyTo (xamcfg.BaseStream);
@@ -252,6 +256,24 @@ protected override string CreateResponseFile ()
 			return responseFile;
 		}
 
+		internal static void WriteObfuscationRules (TextWriter writer, string obfuscationMode)
+		{
+			if (string.Equals (obfuscationMode, "disabled", StringComparison.OrdinalIgnoreCase)) {
+				writer.WriteLine ("-dontobfuscate");
+				return;
+			}
+
+			writer.WriteLine ("-keep,allowshrinking,allowoptimization class **");
+			writer.WriteLine ("-keepclassmembers,allowshrinking,allowoptimization class ** {");
+			writer.WriteLine ("   public protected *;");
+			writer.WriteLine ("}");
+			// Managed interface proxy selection observes Class.getInterfaces(), which R8 cannot infer.
+			writer.WriteLine ("-keep,allowoptimization interface ** {");
+			writer.WriteLine ("   public protected *;");
+			writer.WriteLine ("}");
+			writer.WriteLine ("-keep,allowshrinking class * implements **");
+		}
+
 		// ProGuard "global" options that affect the whole build and are not allowed inside
 		// a library's proguard.txt (the file packaged inside an .aar's root). AGP 9.0
 		// introduced the same restriction — see "Behavior changes" in the AGP 9.0 release

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/PackagingTest.cs

@@ -3,6 +3,7 @@
 using System.IO;
 using System.Linq;
 using System.Text;
+using System.Text.Json;
 using System.Xml.Linq;
 using Microsoft.Build.Framework;
 using NUnit.Framework;
@@ -17,7 +18,9 @@ namespace Xamarin.Android.Build.Tests
 	public class PackagingTest : BaseTest
 	{
 		[Test]
-		public void CheckR8MetadataFilesExist ([Values (AndroidRuntime.CoreCLR, AndroidRuntime.NativeAOT)] AndroidRuntime runtime)
+		public void CheckR8MetadataFilesExist (
+			[Values (AndroidRuntime.CoreCLR, AndroidRuntime.NativeAOT)] AndroidRuntime runtime,
+			[Values ("disabled", "private-members")] string obfuscationMode)
 		{
 			const bool isRelease = true;
 			if (IgnoreUnsupportedConfiguration (runtime, release: isRelease)) {
@@ -29,6 +32,7 @@ public void CheckR8MetadataFilesExist ([Values (AndroidRuntime.CoreCLR, AndroidR
 			};
 			proj.SetRuntime (runtime);
 			proj.SetProperty (proj.ReleaseProperties, KnownProperties.AndroidLinkTool, "r8");
+			proj.SetProperty (proj.ReleaseProperties, KnownProperties.AndroidR8ObfuscationMode, obfuscationMode);
 			// Projects must set $(AndroidCreateProguardMappingFile) to true to opt in
 			proj.SetProperty (proj.ReleaseProperties, "AndroidCreateProguardMappingFile", true);
 			proj.SetProperty ("AndroidPackageFormat", "aab");
@@ -41,7 +45,14 @@ public void CheckR8MetadataFilesExist ([Values (AndroidRuntime.CoreCLR, AndroidR
 				FileAssert.Exists (aab, $"'{aab}' should have been generated.");
 				using (var zip = ZipHelper.OpenZip (aab)) {
 					Assert.IsTrue (zip.Any (e => e.FullName == "BUNDLE-METADATA/com.android.tools.build.obfuscation/proguard.map"), $"AAB file `{aab}` should contain the ProGuard mapping.");
-					Assert.IsTrue (zip.Any (e => e.FullName == "BUNDLE-METADATA/com.android.tools/r8.json"), $"AAB file `{aab}` should contain the R8 build metadata.");
+					var metadata = zip.SingleOrDefault (e => e.FullName == "BUNDLE-METADATA/com.android.tools/r8.json");
+					Assert.IsNotNull (metadata, $"AAB file `{aab}` should contain the R8 build metadata.");
+					using var stream = new MemoryStream ();
+					metadata.Extract (stream);
+					stream.Position = 0;
+					using var document = JsonDocument.Parse (stream);
+					var options = document.RootElement.GetProperty ("options");
+					Assert.AreEqual (obfuscationMode == "private-members", options.GetProperty ("isOptimizationsEnabled").GetBoolean ());
 				}
 
 				Assert.IsTrue (b.Build (proj), "second build should have succeeded.");

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/R8Tests.cs

@@ -48,6 +48,34 @@ public void ReadJavaPackage (string content, string? expected)
 				File.Delete (path);
 			}
 		}
+
+		[Test]
+		public void WritePrivateMemberObfuscationRules ()
+		{
+			using var writer = new StringWriter ();
+			R8.WriteObfuscationRules (writer, "private-members");
+
+			var expected = """
+				-keep,allowshrinking,allowoptimization class **
+				-keepclassmembers,allowshrinking,allowoptimization class ** {
+				   public protected *;
+				}
+				-keep,allowoptimization interface ** {
+				   public protected *;
+				}
+				-keep,allowshrinking class * implements **
+
+				""";
+			Assert.AreEqual (expected.ReplaceLineEndings (System.Environment.NewLine), writer.ToString ());
+		}
+
+		[Test]
+		public void WriteDisabledObfuscationRules ()
+		{
+			using var writer = new StringWriter ();
+			R8.WriteObfuscationRules (writer, "disabled");
+
+			Assert.AreEqual ("-dontobfuscate" + System.Environment.NewLine, writer.ToString ());
+		}
 	}
 }
-

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Android/KnownProperties.cs

@@ -26,6 +26,7 @@ public static class KnownProperties
 		public const string AndroidEnableDesugar = "AndroidEnableDesugar";
 		public const string AndroidManifestMerger = "AndroidManifestMerger";
 		public const string AndroidLinkTool = "AndroidLinkTool";
+		public const string AndroidR8ObfuscationMode = "AndroidR8ObfuscationMode";
 		public const string UseJackAndJill = "UseJackAndJill";
 		public const string AotAssemblies = "AotAssemblies";
 		public const string AndroidEnableProfiledAot = "AndroidEnableProfiledAot";

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64SimpleDotNet.CoreCLR.R8.apkdesc

@@ -5,7 +5,7 @@
       "Size": 3036
     },
     "classes.dex": {
-      "Size": 402716
+      "Size": 382236
     },
     "lib/arm64-v8a/libassembly-store.so": {
       "Size": 2529368
@@ -59,5 +59,5 @@
       "Size": 1904
     }
   },
-  "PackageSize": 6751675
+  "PackageSize": 6743483
 }

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.ProjectTools/Resources/Base/BuildReleaseArm64XFormsDotNet.CoreCLR.R8.apkdesc

@@ -5,7 +5,7 @@
       "Size": 6652
     },
     "classes.dex": {
-      "Size": 3238292
+      "Size": 2794604
     },
     "kotlin/annotation/annotation.kotlin_builtins": {
       "Size": 928
@@ -29,16 +29,16 @@
       "Size": 2396
     },
     "lib/arm64-v8a/libassembly-store.so": {
-      "Size": 9453656
+      "Size": 9458208
     },
     "lib/arm64-v8a/libclrjit.so": {
-      "Size": 2818032
+      "Size": 2818048
     },
     "lib/arm64-v8a/libcoreclr.so": {
-      "Size": 4844000
+      "Size": 4843824
     },
     "lib/arm64-v8a/libmonodroid.so": {
-      "Size": 203592
+      "Size": 204872
     },
     "lib/arm64-v8a/libSystem.Globalization.Native.so": {
       "Size": 72432
@@ -2231,5 +2231,5 @@
       "Size": 794696
     }
   },
-  "PackageSize": 16064019
+  "PackageSize": 15830547
 }

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets

@@ -253,6 +253,7 @@ Copyright (C) 2011-2012 Xamarin. All rights reserved.
 	<AndroidEnableDesugar  Condition=" '$(AndroidEnableDesugar)' == '' ">False</AndroidEnableDesugar>
 	<AndroidD8IgnoreWarnings    Condition=" '$(AndroidD8IgnoreWarnings)' == '' ">True</AndroidD8IgnoreWarnings>
 	<AndroidR8IgnoreWarnings    Condition=" '$(AndroidR8IgnoreWarnings)' == '' ">True</AndroidR8IgnoreWarnings>
+	<AndroidR8ObfuscationMode   Condition=" '$(AndroidR8ObfuscationMode)' == '' ">private-members</AndroidR8ObfuscationMode>
 	<AndroidCreateProguardMappingFile Condition="'$(AndroidCreateProguardMappingFile)' == '' And '$(AndroidLinkTool)' == 'r8'">True</AndroidCreateProguardMappingFile>
 
 	<!-- Figure out which is the main packaging format we want-->
@@ -975,6 +976,7 @@ because xbuild doesn't support framework reference assemblies.
 		<_PropertyCacheItems Include="AndroidEnableProfiledAot=$(AndroidEnableProfiledAot)" />
 		<_PropertyCacheItems Include="AndroidDexTool=$(AndroidDexTool)" />
 		<_PropertyCacheItems Include="AndroidLinkTool=$(AndroidLinkTool)" />
+		<_PropertyCacheItems Include="AndroidR8ObfuscationMode=$(AndroidR8ObfuscationMode)" />
 		<_PropertyCacheItems Include="AndroidLinkResources=$(AndroidLinkResources)" />
 		<_PropertyCacheItems Include="AndroidBundleToolExtraArgs=$(AndroidBundleToolExtraArgs)" />
 		<_PropertyCacheItems Include="AndroidKeyStore=$(AndroidKeyStore)" />
@@ -2026,7 +2028,8 @@ because xbuild doesn't support framework reference assemblies.
     <_ProguardConfiguration Include="$(ProguardConfigFiles)" />
   </ItemGroup>
   <ItemGroup Condition=" '$(ProguardConfigFiles)' == '' ">
-    <_ProguardConfiguration Include="$(MSBuildThisFileDirectory)proguard-android.txt" />
+    <_ProguardConfiguration Include="$(MSBuildThisFileDirectory)proguard-android.txt"          Condition=" '$(AndroidR8ObfuscationMode)' == 'disabled' " />
+    <_ProguardConfiguration Include="$(MSBuildThisFileDirectory)proguard-android-optimize.txt" Condition=" '$(AndroidR8ObfuscationMode)' != 'disabled' " />
     <_ProguardConfiguration Include="$(IntermediateOutputPath)proguard\proguard_xamarin.cfg"         Condition=" '$(AndroidLinkTool)' != '' " />
     <_ProguardConfiguration Include="$(_ProguardProjectConfiguration)"                               Condition=" '$(AndroidLinkTool)' != '' " />
     <_ProguardConfiguration Include="$(IntermediateOutputPath)proguard\proguard_project_primary.cfg" Condition=" '$(AndroidLinkTool)' != '' " />

src/Xamarin.Android.Build.Tasks/Xamarin.Android.D8.targets

@@ -81,6 +81,7 @@ Copyright (C) 2018 Xamarin. All rights reserved.
         BuildMetadataFileOutput="$(_AndroidR8BuildMetadataFile)"
         ProguardConfigurationFiles="@(_ProguardConfiguration)"
         UseTrimmableNativeAotProguardConfiguration="$(_UseTrimmableNativeAotProguardConfiguration)"
+        ObfuscationMode="$(AndroidR8ObfuscationMode)"
         EnableShrinking="$(_R8EnableShrinking)"
         EnableMultiDex="$(AndroidEnableMultiDex)"
         MultiDexMainDexListFile="$(_AndroidMainDexListFile)"

src/proguard-android/proguard-android.targets

@@ -1,29 +1,35 @@
 <Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <_Destination>$(MicrosoftAndroidSdkOutDir)proguard-android.txt</_Destination>
+    <_OptimizeDestination>$(MicrosoftAndroidSdkOutDir)proguard-android-optimize.txt</_OptimizeDestination>
   </PropertyGroup>
 
   <Target Name="_GenerateProGuardRules"
       BeforeTargets="Build"
       Inputs="$(MSBuildThisFile);build.gradle;settings.gradle"
-      Outputs="$(_Destination)">
+      Outputs="$(_Destination);$(_OptimizeDestination)">
     <Exec
         Command="&quot;$(GradleWPath)&quot; extractProguardFiles $(GradleArgs)"
         EnvironmentVariables="JAVA_HOME=$(JavaSdkDirectory);APP_HOME=$(GradleHome)"
         WorkingDirectory="$(MSBuildThisFileDirectory)"
     />
     <ItemGroup>
-      <_ProguardRules Include="$(MSBuildThisFileDirectory)build\intermediates\default_proguard_files\global\proguard-android.txt-*" />
+      <_ProguardRules Include="$(MSBuildThisFileDirectory)build\intermediates\default_proguard_files\global\proguard-android.txt-*">
+        <Destination>$(_Destination)</Destination>
+      </_ProguardRules>
+      <_ProguardRules Include="$(MSBuildThisFileDirectory)build\intermediates\default_proguard_files\global\proguard-android-optimize.txt-*">
+        <Destination>$(_OptimizeDestination)</Destination>
+      </_ProguardRules>
     </ItemGroup>
     <Copy
         SourceFiles="@(_ProguardRules)"
-        DestinationFiles="$(_Destination)"
+        DestinationFiles="@(_ProguardRules->'%(Destination)')"
     />
-    <Touch Files="$(_Destination)" />
+    <Touch Files="$(_Destination);$(_OptimizeDestination)" />
   </Target>
 
   <Target Name="_CleanProguardRules" BeforeTargets="Clean">
-    <Delete Files="$(_Destination)" />
+    <Delete Files="$(_Destination);$(_OptimizeDestination)" />
     <Exec
         Command="&quot;$(GradleWPath)&quot; clean $(GradleArgs)"
         EnvironmentVariables="JAVA_HOME=$(JavaSdkDirectory);APP_HOME=$(GradleHome)"