Add option to enable resource cycle shrinking.

This will instruct AAPT2 to produce conditional keep rules to allow for more aggressive code and resource shrinking.

RELNOTES[NEW]: Add --experimental_android_resource_cycle_shrinking option to allow for more aggressive code and resource shrinking.

PiperOrigin-RevId: 176530749

4 files changed, 50 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidBinary.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidBinary.java
index 1bfcac40af..4d389e94d8 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidBinary.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidBinary.java
@@ -217,6 +217,8 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
             configurationMap,
             cppSemantics);
 
+    boolean shrinkResources = shouldShrinkResources(ruleContext);
+
     // TODO(bazel-team): Resolve all the different cases of resource handling so this conditional
     // can go away: recompile from android_resources, and recompile from android_binary attributes.
     ApplicationManifest applicationManifest;
@@ -250,6 +252,7 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
               ruleContext.attributes().get("crunch_png", Type.BOOLEAN),
               ProguardHelper.getProguardConfigArtifact(ruleContext, ""),
               createMainDexProguardSpec(ruleContext),
+              shouldShrinkResourceCycles(ruleContext, shrinkResources),
               ruleContext.getImplicitOutputArtifact(AndroidRuleClasses.ANDROID_PROCESSED_MANIFEST),
               ruleContext.getImplicitOutputArtifact(AndroidRuleClasses.ANDROID_RESOURCES_ZIP),
               DataBinding.isEnabled(ruleContext)
@@ -294,8 +297,6 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
 
     }
 
-    boolean shrinkResources = shouldShrinkResources(ruleContext);
-
     // Remove the library resource JARs from the binary's runtime classpath.
     // Resource classes from android_library dependencies are replaced by the binary's resource
     // class. We remove them only at the top level so that resources included by a library that is
@@ -785,6 +786,18 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
     return (state == TriState.YES);
   }
 
+  /** Returns {@code true} if resource shrinking should be performed. */
+  private static boolean shouldShrinkResourceCycles(
+      RuleContext ruleContext, boolean shrinkResources) throws RuleErrorException {
+    boolean global =
+        ruleContext.getFragment(AndroidConfiguration.class).useAndroidResourceCycleShrinking();
+    if (global && !shrinkResources) {
+      throw ruleContext.throwWithRuleError(
+          "resource cycle shrinking can only be enabled when resource shrinking is enabled");
+    }
+    return global;
+  }
+
   private static ResourceApk shrinkResources(
       RuleContext ruleContext,
       ResourceApk resourceApk,
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java
index 41d9f50e02..6b48275d3f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidConfiguration.java
@@ -524,6 +524,18 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     public boolean useAndroidResourceShrinking;
 
     @Option(
+      name = "experimental_android_resource_cycle_shrinking",
+      defaultValue = "false",
+      category = "semantics",
+      documentationCategory = OptionDocumentationCategory.UNCATEGORIZED,
+      effectTags = {OptionEffectTag.UNKNOWN},
+      help =
+          "Enables more shrinking of code and resources by instructing AAPT2 "
+              + "to emit conditional Proguard keep rules."
+    )
+    public boolean useAndroidResourceCycleShrinking;
+
+    @Option(
       name = "android_manifest_merger",
       defaultValue = "android",
       category = "semantics",
@@ -727,6 +739,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
   private final boolean useRexToCompressDexFiles;
   private final boolean allowAndroidLibraryDepsWithoutSrcs;
   private final boolean useAndroidResourceShrinking;
+  private final boolean useAndroidResourceCycleShrinking;
   private final AndroidManifestMerger manifestMerger;
   private final ApkSigningMethod apkSigningMethod;
   private final boolean useSingleJarApkBuilder;
@@ -763,6 +776,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     this.allowAndroidLibraryDepsWithoutSrcs = options.allowAndroidLibraryDepsWithoutSrcs;
     this.useAndroidResourceShrinking = options.useAndroidResourceShrinking
         || options.useExperimentalAndroidResourceShrinking;
+    this.useAndroidResourceCycleShrinking = options.useAndroidResourceCycleShrinking;
     this.manifestMerger = options.manifestMerger;
     this.apkSigningMethod = options.apkSigningMethod;
     this.useSingleJarApkBuilder = options.useSingleJarApkBuilder;
@@ -884,6 +898,10 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     return useAndroidResourceShrinking;
   }
 
+  public boolean useAndroidResourceCycleShrinking() {
+    return useAndroidResourceCycleShrinking;
+  }
+
   public AndroidAaptVersion getAndroidAaptVersion() {
     return androidAaptVersion;
   }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourcesProcessorBuilder.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourcesProcessorBuilder.java
index 0adb8b52cd..368fee5d40 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourcesProcessorBuilder.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidResourcesProcessorBuilder.java
@@ -77,6 +77,7 @@ public class AndroidResourcesProcessorBuilder {
   private ResourceDependencies dependencies;
   private Artifact proguardOut;
   private Artifact mainDexProguardOut;
+  private boolean conditionalKeepRules;
   private Artifact rTxtOut;
   private Artifact sourceJarOut;
   private boolean debug = false;
@@ -165,6 +166,11 @@ public class AndroidResourcesProcessorBuilder {
     return this;
   }
 
+  public AndroidResourcesProcessorBuilder conditionalKeepRules(boolean conditionalKeepRules) {
+    this.conditionalKeepRules = conditionalKeepRules;
+    return this;
+  }
+
   public AndroidResourcesProcessorBuilder setMainDexProguardOut(Artifact mainDexProguardCfg) {
     this.mainDexProguardOut = mainDexProguardCfg;
     return this;
@@ -301,6 +307,10 @@ public class AndroidResourcesProcessorBuilder {
       builder.add("--useCompiledResourcesForMerge");
     }
 
+    if (conditionalKeepRules) {
+      builder.add("--conditionalKeepRules");
+    }
+
     configureCommonFlags(outs, inputs, builder);
 
     ParamFileInfo.Builder paramFileInfo = ParamFileInfo.builder(ParameterFileType.SHELL_QUOTED);
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/ApplicationManifest.java b/src/main/java/com/google/devtools/build/lib/rules/android/ApplicationManifest.java
index e378f54fba..70ef13b9aa 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/ApplicationManifest.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/ApplicationManifest.java
@@ -585,6 +585,7 @@ public final class ApplicationManifest {
       boolean crunchPng,
       Artifact proguardCfg,
       @Nullable Artifact mainDexProguardCfg,
+      boolean conditionalKeepRules,
       Artifact manifestOut,
       Artifact mergedResources,
       @Nullable Artifact dataBindingInfoZip,
@@ -623,6 +624,11 @@ public final class ApplicationManifest {
     boolean skipParsingAction =
         targetAaptVersion == AndroidAaptVersion.AAPT2 && androidConfiguration.skipParsingAction();
 
+    if (conditionalKeepRules && targetAaptVersion != AndroidAaptVersion.AAPT2) {
+      throw ruleContext.throwWithRuleError(
+          "resource cycle shrinking can only be enabled for builds with aapt2");
+    }
+
     ResourceContainer processed =
         new AndroidResourcesProcessorBuilder(ruleContext)
             .setLibrary(false)
@@ -638,6 +644,7 @@ public final class ApplicationManifest {
             .withDependencies(resourceDeps)
             .setProguardOut(proguardCfg)
             .setMainDexProguardOut(mainDexProguardCfg)
+            .conditionalKeepRules(conditionalKeepRules)
             .setDataBindingInfoZip(dataBindingInfoZip)
             .setApplicationId(manifestValues.get("applicationId"))
             .setVersionCode(manifestValues.get("versionCode"))