[J2KT] Add -objCNamePrefix option to the transpiler, which defaults…

… to `"J2kt"` to preserve compatibility with existing clients. When ObjC name prefix is empty, ObjC compatibility aliases won't be rendered.

PiperOrigin-RevId: 734100724

transpiler/java/com/google/j2cl/transpiler/BazelJ2clBuilder.java

@@ -143,6 +143,9 @@ final class BazelJ2clBuilder extends BazelWorker {
   @Option(name = "-experimentalDefineForWasm", handler = MapOptionHandler.class, hidden = true)
   Map<String, String> definesForWasm = new HashMap<>();
 
+  @Option(name = "-objCNamePrefix", hidden = true)
+  String objCNamePrefix = "J2kt";
+
   @Override
   protected void run() {
     problems.abortIfCancelled();
@@ -225,6 +228,7 @@ private J2clTranspilerOptions createOptions(Output output) {
         .setNullMarkedSupported(this.enableJSpecifySupport)
         .setKotlincOptions(kotlincOptions)
         .setForbiddenAnnotations(forbiddenAnnotations)
+        .setObjCNamePrefix(objCNamePrefix)
         .build(problems);
   }
 

transpiler/java/com/google/j2cl/transpiler/J2clCommandLineRunner.java

@@ -128,6 +128,9 @@ public final class J2clCommandLineRunner extends CommandLineTool {
   @Option(name = "-defineForWasm", handler = MapOptionHandler.class, hidden = true)
   Map<String, String> definesForWasm = new HashMap<>();
 
+  @Option(name = "-objCNamePrefix", hidden = true)
+  String objCNamePrefix = "J2kt";
+
   private J2clCommandLineRunner() {
     super("j2cl");
   }
@@ -201,6 +204,7 @@ private J2clTranspilerOptions createOptions(Output output) {
         .setNullMarkedSupported(this.enableJSpecifySupport)
         .setKotlincOptions(kotlincOptions)
         .setForbiddenAnnotations(forbiddenAnnotations)
+        .setObjCNamePrefix("J2kt")
         .build(problems);
   }
 

transpiler/java/com/google/j2cl/transpiler/J2clTranspilerOptions.java

@@ -104,6 +104,8 @@ public Builder setWasmEntryPointStrings(List<String> wasmEntryPoints) {
 
     public abstract Builder setForbiddenAnnotations(List<String> forbiddenAnnotations);
 
+    public abstract Builder setObjCNamePrefix(String objCNamePrefix);
+
     abstract J2clTranspilerOptions autoBuild();
 
     public J2clTranspilerOptions build(Problems problems) {

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

@@ -694,7 +694,7 @@ public boolean isWasm() {
   KOTLIN {
     @Override
     public void generateOutputs(BackendOptions options, Library library, Problems problems) {
-      new KotlinGeneratorStage(options.getOutput(), problems, /* withJ2ktPrefix= */ true)
+      new KotlinGeneratorStage(options.getOutput(), problems, options.getObjCNamePrefix())
           .generateOutputs(library);
     }
 

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

@@ -50,4 +50,6 @@ public interface BackendOptions {
   boolean getGenerateKytheIndexingMetadata();
 
   boolean isNullMarkedSupported();
+
+  String getObjCNamePrefix();
 }

transpiler/java/com/google/j2cl/transpiler/backend/kotlin/J2ObjCCompatRenderer.kt

@@ -86,7 +86,7 @@ import com.google.j2cl.transpiler.backend.kotlin.source.Source.Companion.join
 import com.google.j2cl.transpiler.backend.kotlin.source.Source.Companion.source
 import com.google.j2cl.transpiler.backend.kotlin.source.Source.Companion.spaceSeparated
 
-internal class J2ObjCCompatRenderer(private val withJ2ktPrefix: Boolean) {
+internal class J2ObjCCompatRenderer(private val objCNamePrefix: String) {
   internal fun source(compilationUnit: CompilationUnit): Source =
     dependenciesAndDeclarationsSource(compilationUnit).ifNotEmpty {
       emptyLineSeparated(fileCommentSource(compilationUnit), it) + Source.NEW_LINE
@@ -113,9 +113,11 @@ internal class J2ObjCCompatRenderer(private val withJ2ktPrefix: Boolean) {
   private fun shouldRender(type: Type): Boolean = shouldRender(type.declaration)
 
   private fun declarationsRenderers(type: Type): List<Renderer<Source>> = buildList {
-    add(aliasDeclarationRenderer(type.declaration))
-
-    type.toCompanionObjectOrNull()?.let { add(aliasDeclarationRenderer(it.declaration)) }
+    // Don't render compatibility aliases if ObjC name prefix is empty.
+    if (objCNamePrefix.isNotEmpty()) {
+      add(aliasDeclarationRenderer(type.declaration))
+      type.toCompanionObjectOrNull()?.let { add(aliasDeclarationRenderer(it.declaration)) }
+    }
 
     if (type.isEnum) {
       add(nsEnumTypedefRenderer(type))
@@ -388,7 +390,7 @@ internal class J2ObjCCompatRenderer(private val withJ2ktPrefix: Boolean) {
     rendererOf(source(variable.name.objCName.escapeObjCKeyword))
 
   private fun objCNameRenderer(companionDeclaration: CompanionDeclaration): Renderer<Source> =
-    className(companionDeclaration.objCName(withJ2ktPrefix))
+    className(companionDeclaration.objCName(objCNamePrefix))
 
   private fun sharedRenderer(companionDeclaration: CompanionDeclaration): Renderer<Source> =
     getProperty(objCNameRenderer(companionDeclaration), "shared")
@@ -412,7 +414,7 @@ internal class J2ObjCCompatRenderer(private val withJ2ktPrefix: Boolean) {
     }
 
   private fun nonMappedObjCNameRenderer(typeDeclaration: TypeDeclaration): Renderer<Source> =
-    objCNameRenderer(typeDeclaration.kind, typeDeclaration.objCName(withPrefix = withJ2ktPrefix))
+    objCNameRenderer(typeDeclaration.kind, typeDeclaration.objCName(prefix = objCNamePrefix))
 
   private fun objCNameRenderer(kind: TypeDeclaration.Kind, name: String): Renderer<Source> =
     when (kind) {

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

@@ -34,11 +34,12 @@ import com.google.j2cl.transpiler.backend.kotlin.source.Source
  *
  * @property output output for generated sources
  * @property problems problems collected during generation
+ * @property objCNamePrefix ObjCName prefix for types
  */
 class KotlinGeneratorStage(
   private val output: OutputUtils.Output,
   private val problems: Problems,
-  private val withJ2ktPrefix: Boolean,
+  private val objCNamePrefix: String,
 ) {
   /** Generate outputs for a library. */
   fun generateOutputs(library: Library) {
@@ -61,7 +62,7 @@ class KotlinGeneratorStage(
 
   /** Generate ObjC outputs for a compilation unit. */
   private fun generateObjCOutputs(compilationUnit: CompilationUnit) {
-    val source = J2ObjCCompatRenderer(withJ2ktPrefix).source(compilationUnit)
+    val source = J2ObjCCompatRenderer(objCNamePrefix).source(compilationUnit)
     if (source.isNotEmpty()) {
       val path = compilationUnit.packageRelativePath.replace(".java", "+J2ObjCCompat.h")
       output.write(path, source.buildString())
@@ -81,7 +82,7 @@ class KotlinGeneratorStage(
       )
 
     val nameRenderer =
-      NameRenderer(environment, withJ2ktPrefix).plusLocalTypeNameMap(compilationUnit.localTypeNames)
+      NameRenderer(environment, objCNamePrefix).plusLocalTypeNameMap(compilationUnit.localTypeNames)
 
     val compilationUnitRenderer = CompilationUnitRenderer(nameRenderer)
 

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

@@ -32,16 +32,16 @@ import com.google.j2cl.transpiler.backend.kotlin.source.Source
 internal data class NameRenderer
 private constructor(
   val environment: Environment,
-  val withJ2ktPrefix: Boolean,
+  val objCNamePrefix: String,
   private val localTypeNameMap: Map<String, String>,
   private val localFieldNames: Set<String>,
 ) {
   constructor(
     environment: Environment,
-    withJ2ktPrefix: Boolean,
+    objCNamePrefix: String,
   ) : this(
     environment,
-    withJ2ktPrefix = withJ2ktPrefix,
+    objCNamePrefix = objCNamePrefix,
     localTypeNameMap = mapOf(),
     localFieldNames = setOf(),
   )

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

@@ -55,7 +55,7 @@ internal class ObjCNameRenderer(val nameRenderer: NameRenderer) {
   fun objCAnnotationSource(typeDeclaration: TypeDeclaration): Source =
     Source.emptyUnless(needsObjCNameAnnotation(typeDeclaration)) {
       objCNameAnnotationSource(
-        typeDeclaration.objCName(nameRenderer.withJ2ktPrefix),
+        typeDeclaration.objCName(nameRenderer.objCNamePrefix),
         swiftName = typeDeclaration.objCNameWithoutPrefix,
         exact = true,
       )
@@ -64,7 +64,7 @@ internal class ObjCNameRenderer(val nameRenderer: NameRenderer) {
   fun objCAnnotationSource(companionObject: CompanionObject): Source =
     Source.emptyUnless(needsObjCNameAnnotation(companionObject)) {
       objCNameAnnotationSource(
-        companionObject.declaration.objCName(nameRenderer.withJ2ktPrefix),
+        companionObject.declaration.objCName(nameRenderer.objCNamePrefix),
         swiftName = companionObject.declaration.objCNameWithoutPrefix,
         exact = true,
       )

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

@@ -113,19 +113,16 @@ internal fun Method.toNonConstructorObjCNames(): MethodObjCNames =
 private val String.objCMethodParameterNames: List<String>
   get() = letIf(lastOrNull() == ':') { dropLast(1) }.split(":")
 
-private const val OBJC_TYPE_NAME_PREFIX: String = "J2kt"
-
-internal fun TypeDeclaration.objCName(withPrefix: Boolean): String =
-  objCNameWithoutPrefix.letIf(withPrefix) { OBJC_TYPE_NAME_PREFIX + it }
+internal fun TypeDeclaration.objCName(prefix: String): String = prefix + objCNameWithoutPrefix
 
 internal val TypeDeclaration.objCNameWithoutPrefix: String
   get() = mappedObjCName ?: nonMappedObjCName
 
 private val String.objCCompanionTypeName: String
   get() = this + "Companion"
 
-internal fun CompanionDeclaration.objCName(withPrefix: Boolean) =
-  enclosingTypeDeclaration.objCName(withPrefix).objCCompanionTypeName
+internal fun CompanionDeclaration.objCName(prefix: String) =
+  enclosingTypeDeclaration.objCName(prefix).objCCompanionTypeName
 
 internal val CompanionDeclaration.objCNameWithoutPrefix
   get() = enclosingTypeDeclaration.objCNameWithoutPrefix.objCCompanionTypeName