Support optimizing AutoValue-generated code that comes in from J2KT

On the J2KT side we'll be leaving marker annotation on the original `@AutoValue`
annotated classes to denote that it was an AutoValue type. In the Kotlin
frontend we'll then honor that annotation as being equivalent to `@AutoValue`.

In the optimization pass we primarily just need to remove the companion class
that exists for the generated subtype. The only reason it exists is due to the
static `serialVersionUID` field (which we normally expect), but the fact that
it was on the companion object means we'll have a companion class, the companion
instance field on the enclosing type, and the initialization of the companion
field. All of these need to be removed if the enclosing type is eligible for
optimization.

PiperOrigin-RevId: 718994922

transpiler/java/com/google/j2cl/transpiler/ast/DeclaredTypeDescriptor.java

@@ -135,13 +135,8 @@ public boolean isNoopCast() {
     return getTypeDeclaration().isNoopCast();
   }
 
-  /**
-   * Returns true if the given type descriptor is a Kotlin companion object class that can be
-   * optimized. In order to be optimizable, the companion object should not extend any class nor
-   * implement any interface.
-   */
   @Override
-  public boolean isOptimizableKotlinCompanion() {
+  public boolean isKotlinCompanionClass() {
     // TODO(b/337362819): Uncomment this when the Java frontend is correctly settings SourceLanguage
     // for Kotlin deps.
     // if (getTypeDeclaration().getSourceLanguage() != KOTLIN) {
@@ -152,20 +147,26 @@ public boolean isOptimizableKotlinCompanion() {
     // - The type should be a static nested final class named `Companion`
     // - The enclosing class should have a static field named `Companion` of the same type.
     // TODO(b/335000000): Add the ability to mark class as Kotlin companion.
-    if (!isClass()
-        || !isFinal()
-        || !getSimpleSourceName().equals("Companion")
-        || getEnclosingTypeDescriptor() == null
-        || getEnclosingTypeDescriptor().getDeclaredFieldDescriptors().stream()
-            .noneMatch(
-                f ->
-                    f.getName().equals("Companion")
-                        && f.getTypeDescriptor().isSameBaseType(this))) {
-      return false;
-    }
+    return isClass()
+        && isFinal()
+        && getSimpleSourceName().equals("Companion")
+        && getEnclosingTypeDescriptor() != null
+        && getEnclosingTypeDescriptor().getDeclaredFieldDescriptors().stream()
+            .anyMatch(
+                f -> f.getName().equals("Companion") && f.getTypeDescriptor().isSameBaseType(this));
+  }
+
+  /**
+   * Returns true if the given type descriptor is a Kotlin companion object class that can be
+   * optimized. In order to be optimizable, the companion object should not extend any class nor
+   * implement any interface.
+   */
+  @Override
+  public boolean isOptimizableKotlinCompanion() {
     // In order to be able to optimize the companion object, it should not extend any class nor
     // implement any interface.
-    return TypeDescriptors.isJavaLangObject(getSuperTypeDescriptor())
+    return isKotlinCompanionClass()
+        && TypeDescriptors.isJavaLangObject(getSuperTypeDescriptor())
         && getInterfaceTypeDescriptors().isEmpty();
   }
 

transpiler/java/com/google/j2cl/transpiler/ast/TypeDescriptor.java

@@ -343,6 +343,11 @@ public boolean isNoopCast() {
     return false;
   }
 
+  /** Returns true if the given type descriptor is a Kotlin companion object class. */
+  public boolean isKotlinCompanionClass() {
+    return false;
+  }
+
   /**
    * Returns true if the given type descriptor is a Kotlin companion object class that can be
    * optimized.

transpiler/java/com/google/j2cl/transpiler/backend/Backend.java

@@ -256,8 +256,8 @@ public ImmutableList<Supplier<NormalizationPass>> getPassFactories(BackendOption
           // Compute bridge methods before optimizing autovalue, since inlining the autovalue
           // classes requires inlining the bridges as well.
           AddBridgeMethods::new,
-          () -> new OptimizeAutoValue(options.getOptimizeAutoValue()),
           OptimizeKotlinCompanions::new,
+          () -> new OptimizeAutoValue(options.getOptimizeAutoValue()),
 
           // Default constructors and explicit super calls should be synthesized first.
           CreateImplicitConstructors::new,

transpiler/java/com/google/j2cl/transpiler/backend/kotlin/TypeRenderer.kt

@@ -22,6 +22,7 @@ import com.google.j2cl.transpiler.ast.TypeDeclaration
 import com.google.j2cl.transpiler.ast.TypeDescriptor
 import com.google.j2cl.transpiler.ast.TypeDescriptors.isJavaLangEnum
 import com.google.j2cl.transpiler.ast.TypeDescriptors.isJavaLangObject
+import com.google.j2cl.transpiler.backend.kotlin.KotlinSource.annotation
 import com.google.j2cl.transpiler.backend.kotlin.objc.comment
 import com.google.j2cl.transpiler.backend.kotlin.source.Source
 import com.google.j2cl.transpiler.backend.kotlin.source.Source.Companion.block
@@ -65,6 +66,7 @@ internal data class TypeRenderer(val nameRenderer: NameRenderer) {
           newLineSeparated(
             objCNameRenderer.objCAnnotationSource(typeDeclaration),
             jsInteropAnnotationRenderer.jsInteropAnnotationsSource(typeDeclaration),
+            autoValueAnnotationsSource(typeDeclaration),
             spaceSeparated(
               inheritanceModifierSource(typeDeclaration),
               classModifiersSource(typeDeclaration),
@@ -156,6 +158,19 @@ internal data class TypeRenderer(val nameRenderer: NameRenderer) {
     getConstructorInvocation(method)?.let { expressionRenderer(type).invocationSource(it) }
       ?: inParentheses(Source.EMPTY)
 
+  private fun autoValueAnnotationsSource(typeDeclaration: TypeDeclaration): Source =
+    when {
+      typeDeclaration.isAnnotatedWithAutoValue ->
+        annotation(
+          nameRenderer.topLevelQualifiedNameSource("javaemul.lang.annotations.WasAutoValue")
+        )
+      typeDeclaration.isAnnotatedWithAutoValueBuilder ->
+        annotation(
+          nameRenderer.topLevelQualifiedNameSource("javaemul.lang.annotations.WasAutoValue.Builder")
+        )
+      else -> Source.EMPTY
+    }
+
   private companion object {
     fun classModifiersSource(typeDeclaration: TypeDeclaration): Source =
       Source.emptyUnless(typeDeclaration.isKtInner) { KotlinSource.INNER_KEYWORD }

transpiler/java/com/google/j2cl/transpiler/frontend/kotlin/KotlinEnvironment.kt

@@ -49,6 +49,8 @@ import com.google.j2cl.transpiler.frontend.kotlin.ir.getWasmInfo
 import com.google.j2cl.transpiler.frontend.kotlin.ir.hasVoidReturn
 import com.google.j2cl.transpiler.frontend.kotlin.ir.isAbstract
 import com.google.j2cl.transpiler.frontend.kotlin.ir.isArrayType
+import com.google.j2cl.transpiler.frontend.kotlin.ir.isAutoValue
+import com.google.j2cl.transpiler.frontend.kotlin.ir.isAutoValueBuilder
 import com.google.j2cl.transpiler.frontend.kotlin.ir.isCapturingEnclosingInstance
 import com.google.j2cl.transpiler.frontend.kotlin.ir.isClassType
 import com.google.j2cl.transpiler.frontend.kotlin.ir.isDeprecated
@@ -250,6 +252,8 @@ class KotlinEnvironment(
         .setJsFunctionInterface(irClass.isJsFunction)
         .setJsEnumInfo(irClass.getJsEnumInfo())
         .setWasmInfo(irClass.getWasmInfo())
+        .setAnnotatedWithAutoValue(irClass.isAutoValue)
+        .setAnnotatedWithAutoValueBuilder(irClass.isAutoValueBuilder)
         .apply {
           val jsMemberAnnotation = irClass.getJsMemberAnnotationInfo()
           setCustomizedJsNamespace(jsMemberAnnotation?.namespace)

transpiler/java/com/google/j2cl/transpiler/frontend/kotlin/ir/IrUtils.kt

@@ -441,6 +441,16 @@ val IrClass.isFinal: Boolean
 val IrClass.isFromSource: Boolean
   get() = source.containingFile != SourceFile.NO_SOURCE_FILE
 
+val IrClass.isAutoValue: Boolean
+  get() =
+    hasAnnotation(FqName("com.google.auto.value.AutoValue")) ||
+      hasAnnotation(FqName("javaemul.lang.annotations.WasAutoValue"))
+
+val IrClass.isAutoValueBuilder: Boolean
+  get() =
+    hasAnnotation(FqName("com.google.auto.value.AutoValue.Builder")) ||
+      hasAnnotation(FqName("javaemul.lang.annotations.WasAutoValue.Builder"))
+
 fun IrDeclaration.getTopLevelEnclosingClass(): IrClass {
   if (this is IrClass && isTopLevel) {
     return this

transpiler/java/com/google/j2cl/transpiler/passes/JsInteropRestrictionsChecker.java

@@ -219,10 +219,11 @@ private boolean checkAutoValue(TypeDeclaration typeDeclaration) {
   }
 
   private boolean checkAutoValueTypeName(TypeDeclaration typeDeclaration) {
-    // TODO(goktug): Replace with checking the generator name passed via @Generated when J2CL starts
-    // modeling annotations in the AST.
+    // TODO(b/221280581): Replace with checking the generator name passed via @Generated when J2CL
+    //  starts modeling annotations in the AST.
     return typeDeclaration != null
-        && typeDeclaration.getSimpleSourceName().matches("\\$*AutoValue_.+");
+        // Note: We normally expect the name to start with a $, but J2KT will replace that with __.
+        && typeDeclaration.getSimpleSourceName().matches("(\\$|_)*AutoValue_.+");
   }
 
   private void checkSystemProperties(Type type) {

transpiler/java/com/google/j2cl/transpiler/passes/OptimizeKotlinCompanions.java

@@ -31,6 +31,7 @@
 import com.google.j2cl.transpiler.ast.Field;
 import com.google.j2cl.transpiler.ast.FieldAccess;
 import com.google.j2cl.transpiler.ast.FieldDescriptor;
+import com.google.j2cl.transpiler.ast.InitializerBlock;
 import com.google.j2cl.transpiler.ast.JsInfo;
 import com.google.j2cl.transpiler.ast.JsMemberType;
 import com.google.j2cl.transpiler.ast.Method;
@@ -377,8 +378,18 @@ private static void moveCompanionInstanceFieldToCompanionClass(
                         return null;
                       }
                     }));
-    Statement initializer = Iterables.getOnlyElement(initializers);
 
+    // We may have emptied out an initializer block so we should clean those up. This doesn't
+    // guarantee that we're only cleaning up ones we actually touched, but if it's empty it
+    // shouldn't matter anyway.
+    enclosingType
+        .getMembers()
+        .removeIf(
+            m ->
+                m.isInitializerBlock()
+                    && ((InitializerBlock) m).getBody().getStatements().isEmpty());
+
+    Statement initializer = Iterables.getOnlyElement(initializers);
     companion.addStaticInitializerBlock(
         0,
         Block.newBuilder()

transpiler/javatests/com/google/j2cl/integration/java/autovalue/AutoValueDependency.java

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2025 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not
+ * use this file except in compliance with the License. You may obtain a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations under
+ * the License.
+ */
+package autovalue;
+
+import com.google.auto.value.AutoValue;
+
+@AutoValue
+public abstract class AutoValueDependency {
+  abstract int value();
+
+  public static Builder builder() {
+    return new AutoValue_AutoValueDependency.Builder();
+  }
+
+  @AutoValue.Builder
+  public abstract static class Builder {
+    public abstract Builder value(int value);
+
+    public abstract AutoValueDependency build();
+  }
+}

transpiler/javatests/com/google/j2cl/integration/java/autovalue/BUILD

@@ -1,6 +1,7 @@
 load("//build_defs:rules.bzl", "j2wasm_library")
 load(
     "//transpiler/javatests/com/google/j2cl/integration:integration_test.bzl",
+    "integration_library",
     "integration_test",
 )
 
@@ -10,13 +11,25 @@ package(
     licenses = ["notice"],
 )
 
+integration_library(
+    name = "dependency",
+    srcs = ["AutoValueDependency.java"],
+    deps = [
+        "//third_party:auto_value",
+    ],
+)
+
 j2wasm_library(
     name = "autovalue-j2wasm",
     srcs = glob(
         ["*.java"],
-        exclude = ["JsArray.java"],
+        exclude = [
+            "AutoValueDependency.java",
+            "JsArray.java",
+        ],
     ) + glob(["super-wasm/*.java"]),
     deps = [
+        ":dependency-j2wasm",
         "//jre/java:javaemul_internal_annotations-j2wasm",
         "//third_party:auto_value-j2wasm",
         "//third_party:jsinterop-annotations-j2wasm",
@@ -27,9 +40,13 @@ j2wasm_library(
 # TODO(b/264934554): Port this test to Kotlin when AutoValue is supported.
 integration_test(
     name = "autovalue",
-    srcs = glob(["*.java"]),
+    srcs = glob(
+        ["*.java"],
+        exclude = ["AutoValueDependency.java"],
+    ),
     closure_defines = {"jre.classMetadata": "'STRIPPED'"},
     deps = [
+        ":dependency",
         "//third_party:auto_value",
     ],
 )

transpiler/javatests/com/google/j2cl/integration/java/autovalue/Main.java

@@ -41,6 +41,7 @@ public static void main(String... args) {
     testUnusedTypeExtending();
     testClinit();
     testJsInterop();
+    testCrossLibrary();
   }
 
   private static void testComposite() {
@@ -241,6 +242,10 @@ private int getField() {
       return field;
     }
 
+    public static int getStaticField() {
+      return field;
+    }
+
     static {
       field = 1;
     }
@@ -268,6 +273,7 @@ static AutoValueWithBuilderAndClinit create() {
   private static void testClinit() {
     AutoValueWithBuilderAndClinit o = AutoValueWithBuilderAndClinit.Builder.create();
     assertEquals(1, o.getField());
+    assertEquals(1, AutoValueWithBuilderAndClinit.getStaticField());
   }
 
   @AutoValue
@@ -300,4 +306,9 @@ private static void testJsInterop() {
     assertEquals(0, autoValueJsType.getField());
     assertEquals(1, autoValueJsType.getField2());
   }
+
+  private static void testCrossLibrary() {
+    AutoValueDependency dependency = AutoValueDependency.builder().value(1).build();
+    assertEquals(1, dependency.value());
+  }
 }

transpiler/javatests/com/google/j2cl/readable/java/autovalue/output_j2kt_web/AutoValueJsType.impl.java.js.txt

@@ -1,29 +1,55 @@
 goog.module('autovalue.AutoValueJsType$impl');
 
-const j_l_Object = goog.require('java.lang.Object$impl');
+const ValueType = goog.require('javaemul.internal.ValueType$impl');
 const $Util = goog.require('nativebootstrap.Util$impl');
 
-/**
- * @abstract
- */
-class AutoValueJsType extends j_l_Object {
+class AutoValueJsType extends ValueType {
  /** @protected @nodts */
  constructor() {
   super();
+  /**@type {number} @nodts*/
+  this.f_field__autovalue_AutoValue_AutoValueJsType_ = 0;
+  /**@type {number} @nodts*/
+  this.f_withJsMethod__autovalue_AutoValue_AutoValueJsType_ = 0;
+ }
+ /** @nodts @return {!AutoValueJsType} */
+ static $create__() {
+  AutoValueJsType.$clinit();
+  let $instance = new AutoValueJsType();
+  $instance.$ctor__autovalue_AutoValueJsType__void();
+  return $instance;
  }
  /** @nodts */
  $ctor__autovalue_AutoValueJsType__void() {
-  this.$ctor__java_lang_Object__void();
+  this.$ctor__javaemul_internal_ValueType__void();
+ }
+ /** @nodts @return {!AutoValueJsType} */
+ static $create__int__int(/** number */ field, /** number */ withJsMethod) {
+  AutoValueJsType.$clinit();
+  let $instance = new AutoValueJsType();
+  $instance.$ctor__autovalue_AutoValueJsType__int__int__void(field, withJsMethod);
+  return $instance;
+ }
+ /** @nodts */
+ $ctor__autovalue_AutoValueJsType__int__int__void(/** number */ field, /** number */ withJsMethod) {
+  this.$ctor__autovalue_AutoValueJsType__void();
+  this.f_field__autovalue_AutoValue_AutoValueJsType_ = field;
+  this.f_withJsMethod__autovalue_AutoValue_AutoValueJsType_ = withJsMethod;
+  $J2CL_PRESERVE$(this.f_field__autovalue_AutoValue_AutoValueJsType_, this.f_withJsMethod__autovalue_AutoValue_AutoValueJsType_);
+ }
+ /** @return {number} */
+ getField() {
+  return this.f_field__autovalue_AutoValue_AutoValueJsType_;
+ }
+ /** @return {number} */
+ getField2() {
+  return this.f_withJsMethod__autovalue_AutoValue_AutoValueJsType_;
  }
- /** @abstract @return {number} */
- getField() {}
- /** @abstract @return {number} */
- getField2() {}
  /** @nodts */
  static $clinit() {
   AutoValueJsType.$clinit = () =>{};
   AutoValueJsType.$loadModules();
-  j_l_Object.$clinit();
+  ValueType.$clinit();
  }
  /** @nodts @return {boolean} */
  static $isInstance(/** ? */ instance) {

transpiler/javatests/com/google/j2cl/readable/java/autovalue/output_j2kt_web/AutoValueJsType.java.js.txt

@@ -1,6 +1,6 @@
 goog.module('autovalue.AutoValueJsType');
 
-goog.require('java.lang.Object');
+goog.require('javaemul.internal.ValueType');
 goog.require('nativebootstrap.Util');
 
 const AutoValueJsType = goog.require('autovalue.AutoValueJsType$impl');