Hooks to support core library desugaring in Android builds

RELNOTES: None.

PiperOrigin-RevId: 184909685

4 files changed, 115 insertions, 6 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 fc808ae89a..c8b78e5f4a 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
@@ -32,6 +32,7 @@ import com.google.devtools.build.lib.actions.Artifact.SpecialArtifact;
 import com.google.devtools.build.lib.actions.FailAction;
 import com.google.devtools.build.lib.actions.ParameterFile;
 import com.google.devtools.build.lib.analysis.ConfiguredTarget;
+import com.google.devtools.build.lib.analysis.FileProvider;
 import com.google.devtools.build.lib.analysis.FilesToRunProvider;
 import com.google.devtools.build.lib.analysis.OutputGroupInfo;
 import com.google.devtools.build.lib.analysis.RuleConfiguredTargetBuilder;
@@ -150,6 +151,13 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
           "proguard_apply_mapping",
           "'proguard_apply_dictionary' can only be used when 'proguard_specs' is also set");
     }
+
+    if (AndroidCommon.getAndroidConfig(ruleContext).desugarJava8Libs()
+        && getMultidexMode(ruleContext) == MultidexMode.OFF) {
+      // Multidex is required so we can include legacy libs as a separate .dex file.
+      ruleContext.throwWithAttributeError(
+          "multidex", "Support for Java 8 libraries on legacy devices requires multidex");
+    }
   }
 
   private static RuleConfiguredTargetBuilder init(
@@ -397,8 +405,60 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
     FilesToRunProvider resourceExtractor =
         ruleContext.getExecutablePrerequisite("$resource_extractor", Mode.HOST);
 
+    Artifact finalClassesDex;
+    if (AndroidCommon.getAndroidConfig(ruleContext).desugarJava8Libs()
+        && dexPostprocessingOutput.classesDexZip().getFilename().endsWith(".zip")) {
+      Artifact java8LegacyDex;
+      if (binaryJar == jarToDex) {
+        // No Proguard: use canned Java 8 legacy .dex file
+        java8LegacyDex =
+            ruleContext.getPrerequisiteArtifact("$java8_legacy_dex", Mode.TARGET);
+      } else {
+        // Proguard is used: build custom Java 8 legacy .dex file
+        java8LegacyDex = getDxArtifact(ruleContext, "_java8_legacy.dex.zip");
+        Artifact androidJar = AndroidSdkProvider.fromRuleContext(ruleContext).getAndroidJar();
+        ruleContext.registerAction(
+            new SpawnAction.Builder()
+                .setExecutable(
+                    ruleContext.getExecutablePrerequisite("$build_java8_legacy_dex", Mode.HOST))
+                .addInput(jarToDex)
+                .addInput(androidJar)
+                .addOutput(java8LegacyDex)
+                .addCommandLine(
+                    CustomCommandLine.builder()
+                        .addExecPath("--binary", jarToDex)
+                        .addExecPath("--android_jar", androidJar)
+                        .addExecPath("--output", java8LegacyDex)
+                        .build())
+                .setMnemonic("BuildLegacyDex")
+                .setProgressMessage("Building Java 8 legacy library for %s", ruleContext.getLabel())
+                .build(ruleContext));
+      }
+
+      // Append legacy .dex library to app's .dex files
+      finalClassesDex = getDxArtifact(ruleContext, "_final_classes.dex.zip");
+      ruleContext.registerAction(
+          new SpawnAction.Builder()
+              .useDefaultShellEnvironment()
+              .setMnemonic("AppendJava8LegacyDex")
+              .setProgressMessage("Adding Java 8 legacy library for %s", ruleContext.getLabel())
+              .setExecutable(ruleContext.getExecutablePrerequisite("$merge_dexzips", Mode.HOST))
+              .addInput(dexPostprocessingOutput.classesDexZip())
+              .addInput(java8LegacyDex)
+              .addOutput(finalClassesDex)
+              // Order matters here: we want java8LegacyDex to be the highest-numbered classesN.dex
+              .addCommandLine(CustomCommandLine.builder()
+                  .addExecPath("--input_zip", dexPostprocessingOutput.classesDexZip())
+                  .addExecPath("--input_zip", java8LegacyDex)
+                  .addExecPath("--output_zip", finalClassesDex)
+                  .build())
+              .build(ruleContext));
+    } else {
+      finalClassesDex = dexPostprocessingOutput.classesDexZip();
+    }
+
     ApkActionsBuilder.create("apk")
-        .setClassesDex(dexPostprocessingOutput.classesDexZip())
+        .setClassesDex(finalClassesDex)
         .addInputZip(resourceApk.getArtifact())
         .setJavaResourceZip(dexingOutput.javaResourceJar, resourceExtractor)
         .addInputZips(nativeLibsZips)
@@ -596,11 +656,19 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
     }
 
     AndroidSdkProvider sdk = AndroidSdkProvider.fromRuleContext(ruleContext);
-    NestedSet<Artifact> libraryJars =
+    NestedSetBuilder<Artifact> libraryJars =
         NestedSetBuilder.<Artifact>naiveLinkOrder()
-            .add(sdk.getAndroidJar())
-            .addTransitive(common.getTransitiveNeverLinkLibraries())
-            .build();
+            .add(sdk.getAndroidJar());
+    if (AndroidCommon.getAndroidConfig(ruleContext).desugarJava8Libs()) {
+      // Proguard sees the desugared app, so it needs legacy APIs to resolve symbols
+      libraryJars.addTransitive(
+          ruleContext
+              .getPrerequisite("$desugared_java8_legacy_apis", Mode.TARGET)
+              .getProvider(FileProvider.class)
+              .getFilesToBuild());
+    }
+    libraryJars.addTransitive(common.getTransitiveNeverLinkLibraries());
+
     Artifact proguardSeeds =
         ruleContext.getImplicitOutputArtifact(JavaSemantics.JAVA_BINARY_PROGUARD_SEEDS);
     Artifact proguardUsage =
@@ -615,7 +683,7 @@ public abstract class AndroidBinary implements RuleConfiguredTargetFactory {
             proguardUsage,
             proguardMapping,
             proguardDictionary,
-            libraryJars,
+            libraryJars.build(),
             proguardOutputJar,
             javaSemantics,
             getProguardOptimizationPasses(ruleContext),
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 5d824b55f9..ce2bb0178d 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
@@ -394,6 +394,20 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     )
     public boolean desugarJava8;
 
+    @Option(
+      name = "experimental_desugar_java8_libs",
+      defaultValue = "false",
+      documentationCategory = OptionDocumentationCategory.INPUT_STRICTNESS,
+      effectTags = {
+        OptionEffectTag.AFFECTS_OUTPUTS,
+        OptionEffectTag.LOADING_AND_ANALYSIS,
+        OptionEffectTag.LOSES_INCREMENTAL_STATE,
+      },
+      metadataTags = OptionMetadataTag.EXPERIMENTAL,
+      help = "Whether to include supported Java 8 libraries in apps for legacy devices."
+    )
+    public boolean desugarJava8Libs;
+
     // This flag is intended to be flipped globally.
     @Option(
       name = "experimental_check_desugar_deps",
@@ -769,6 +783,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
       host.fatApkCpus = ImmutableList.of(); // Fat APK archs don't apply to the host.
 
       host.desugarJava8 = desugarJava8;
+      host.desugarJava8Libs = desugarJava8Libs;
       host.checkDesugarDeps = checkDesugarDeps;
       host.incrementalDexing = incrementalDexing;
       host.incrementalDexingShardsAfterProguard = incrementalDexingShardsAfterProguard;
@@ -822,6 +837,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
   private final ImmutableList<String> dexoptsSupportedInDexMerger;
   private final boolean useWorkersWithDexbuilder;
   private final boolean desugarJava8;
+  private final boolean desugarJava8Libs;
   private final boolean checkDesugarDeps;
   private final boolean useRexToCompressDexFiles;
   private final boolean allowAndroidLibraryDepsWithoutSrcs;
@@ -856,6 +872,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     this.dexoptsSupportedInDexMerger = ImmutableList.copyOf(options.dexoptsSupportedInDexMerger);
     this.useWorkersWithDexbuilder = options.useWorkersWithDexbuilder;
     this.desugarJava8 = options.desugarJava8;
+    this.desugarJava8Libs = options.desugarJava8Libs;
     this.checkDesugarDeps = options.checkDesugarDeps;
     this.allowAndroidLibraryDepsWithoutSrcs = options.allowAndroidLibraryDepsWithoutSrcs;
     this.useAndroidResourceShrinking =
@@ -879,6 +896,10 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
       throw new InvalidConfigurationException(
           "--experimental_incremental_dexing_after_proguard must be a positive number");
     }
+    if (desugarJava8Libs && !desugarJava8) {
+      throw new InvalidConfigurationException(
+          "Java 8 library support requires --desugar_java8 to be enabled.");
+    }
   }
 
   @AutoCodec.Instantiator
@@ -896,6 +917,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
       ImmutableList<String> dexoptsSupportedInDexMerger,
       boolean useWorkersWithDexbuilder,
       boolean desugarJava8,
+      boolean desugarJava8Libs,
       boolean checkDesugarDeps,
       boolean useRexToCompressDexFiles,
       boolean allowAndroidLibraryDepsWithoutSrcs,
@@ -926,6 +948,7 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     this.dexoptsSupportedInDexMerger = dexoptsSupportedInDexMerger;
     this.useWorkersWithDexbuilder = useWorkersWithDexbuilder;
     this.desugarJava8 = desugarJava8;
+    this.desugarJava8Libs = desugarJava8Libs;
     this.checkDesugarDeps = checkDesugarDeps;
     this.useRexToCompressDexFiles = useRexToCompressDexFiles;
     this.allowAndroidLibraryDepsWithoutSrcs = allowAndroidLibraryDepsWithoutSrcs;
@@ -1013,6 +1036,10 @@ public class AndroidConfiguration extends BuildConfiguration.Fragment {
     return desugarJava8;
   }
 
+  public boolean desugarJava8Libs() {
+    return desugarJava8Libs;
+  }
+
   public boolean checkDesugarDeps() {
     return checkDesugarDeps;
   }
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidRuleClasses.java b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidRuleClasses.java
index 18685069c4..11c95ab531 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/AndroidRuleClasses.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/AndroidRuleClasses.java
@@ -832,6 +832,17 @@ public final class AndroidRuleClasses {
                   .cfg(HostTransition.INSTANCE)
                   .exec()
                   .value(env.getToolsLabel("//tools/android:desugar_java8")))
+          .add(
+              attr("$java8_legacy_dex", LABEL)
+                  .value(env.getToolsLabel("//tools/android:java8_legacy_dex")))
+          .add(
+              attr("$build_java8_legacy_dex", LABEL)
+                  .cfg(HostTransition.INSTANCE)
+                  .exec()
+                  .value(env.getToolsLabel("//tools/android:build_java8_legacy_dex")))
+          .add(
+              attr("$desugared_java8_legacy_apis", LABEL)
+                  .value(env.getToolsLabel("//tools/android:desugared_java8_legacy_apis")))
           /* <!-- #BLAZE_RULE($android_binary_base).ATTRIBUTE(dexopts) -->
           Additional command-line flags for the dx tool when generating classes.dex.
           Subject to <a href="${link make-variables}">"Make variable"</a> substitution and
diff --git a/src/main/java/com/google/devtools/build/lib/rules/android/DexArchiveAspect.java b/src/main/java/com/google/devtools/build/lib/rules/android/DexArchiveAspect.java
index fc938b1b6e..6677f09a67 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/android/DexArchiveAspect.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/android/DexArchiveAspect.java
@@ -399,6 +399,9 @@ public final class DexArchiveAspect extends NativeAspectClass implements Configu
     if (getAndroidConfig(ruleContext).checkDesugarDeps()) {
       args.add("--emit_dependency_metadata_as_needed");
     }
+    if (getAndroidConfig(ruleContext).desugarJava8Libs()) {
+      args.add("--desugar_supported_core_libs");
+    }
 
     ruleContext.registerAction(
         new SpawnAction.Builder()