From d23edcee9fd78eecd0f1e538d844c679ea380246 Mon Sep 17 00:00:00 2001
From: J2ObjC Team <j2objc-copybara@google.com>
Date: Mon, 18 May 2026 01:25:21 -0700
Subject: [PATCH] Use `id<MyJavaInterface>` instead of `MyJavaInterface *` in
 ObjectiveCKmpMethod

Map java interfaces (translated to ObjC protocols) to `id<MyJavaInterface>` rather than `MyJavaInterface *`, which is incorrect in ObjC. Types that are specifically mapped, such as `java.util.List`, are not affected.

PiperOrigin-RevId: 917081023
---
 .../ObjectiveCKmpMethodTranslator.java        | 31 ++++++--
 .../ObjectiveCKmpMethodTranslatorTest.java    | 78 +++++++++++++++++++
 2 files changed, 104 insertions(+), 5 deletions(-)

diff --git a/translator/src/main/java/com/google/devtools/j2objc/translate/ObjectiveCKmpMethodTranslator.java b/translator/src/main/java/com/google/devtools/j2objc/translate/ObjectiveCKmpMethodTranslator.java
index 79c896bdc8..a05e5fef21 100644
--- a/translator/src/main/java/com/google/devtools/j2objc/translate/ObjectiveCKmpMethodTranslator.java
+++ b/translator/src/main/java/com/google/devtools/j2objc/translate/ObjectiveCKmpMethodTranslator.java
@@ -787,17 +787,18 @@ private NativeType calculateNativeType(
     return new NativeType(builder.toString(), null, null, referencedTypes);
   }
 
-  private String toNativeType(
+  private PrintableNativeType toNativeType(
       TypeMirror typeMirror, ExecutableElement methodExecutable, List<TypeMirror> referencedTypes) {
     String fullyQualifiedNameJavaName = TypeUtil.getQualifiedName(typeMirror);
     String nativeType = JAVA_TO_NATIVE_TYPE_MAP.get(fullyQualifiedNameJavaName);
     if (nativeType != null) {
-      return nativeType;
+      return new PrintableNativeType(nativeType, false);
     }
     TypeElement typeElement = TypeUtil.asTypeElement(typeMirror);
     if (typeElement != null) {
       referencedTypes.add(typeMirror);
-      return nameTable.getFullName(typeElement);
+      return new PrintableNativeType(
+          nameTable.getFullName(typeElement), TypeUtil.isInterface(typeMirror));
     }
     throw new IllegalArgumentException(
         "Unsupported type: " + fullyQualifiedNameJavaName + " in method: " + methodExecutable);
@@ -820,6 +821,8 @@ private boolean isTypeSupported(TypeMirror typeMirror) {
    *   <li>{@code List<String>} becomes {@code NSArray<NSString *> *}
    *   <li>{@code Map<Integer, String>} becomes {@code NSDictionary<NSNumber *, NSString *> *}
    *   <li>{@code Set<List<String>>} becomes {@code NSSet<NSArray<NSString *> *> *}
+   *   <li>{@code JavaInterface} becomes {@code id<JavaInterface>}
+   *   <li>{@code List<JavaInterface>} becomes {@code NSArray<id<JavaInterface>> *}
    * </ul>
    */
   private class NativeTypeVisitor extends SimpleTypeVisitor9<Void, StringBuilder> {
@@ -835,13 +838,21 @@ private NativeTypeVisitor(
 
     @Override
     public Void visitDeclared(DeclaredType type, StringBuilder builder) {
-      builder.append(toNativeType(type, methodExecutable, referencedTypes));
+      PrintableNativeType nativeType = toNativeType(type, methodExecutable, referencedTypes);
+      if (nativeType.isUntranslatedInterface) {
+        builder.append("id<");
+      }
+      builder.append(nativeType.nativeTypeName);
       List<? extends TypeMirror> typeArguments = type.getTypeArguments();
       if (options.asObjCGenericDecl() && !typeArguments.isEmpty()) {
         String typeArgsString = buildTypeArgumentString(typeArguments);
         builder.append("<").append(typeArgsString).append(">");
       }
-      builder.append(" *");
+      if (nativeType.isUntranslatedInterface) {
+        builder.append(">");
+      } else {
+        builder.append(" *");
+      }
       return null;
     }
 
@@ -937,4 +948,14 @@ abstract AdapterLookup.ConverterMatch findParamConverter(
     abstract TypeMirror getReturnCastType(
         TypeMirror originalMethodReturnType, TypeMirror adapterReturnType);
   }
+
+  private static final class PrintableNativeType {
+    private final String nativeTypeName;
+    private final boolean isUntranslatedInterface;
+
+    PrintableNativeType(String nativeTypeName, boolean isUntranslatedInterface) {
+      this.nativeTypeName = nativeTypeName;
+      this.isUntranslatedInterface = isUntranslatedInterface;
+    }
+  }
 }
diff --git a/translator/src/test/java/com/google/devtools/j2objc/translate/ObjectiveCKmpMethodTranslatorTest.java b/translator/src/test/java/com/google/devtools/j2objc/translate/ObjectiveCKmpMethodTranslatorTest.java
index 412d3397ae..54b44a4fe0 100644
--- a/translator/src/test/java/com/google/devtools/j2objc/translate/ObjectiveCKmpMethodTranslatorTest.java
+++ b/translator/src/test/java/com/google/devtools/j2objc/translate/ObjectiveCKmpMethodTranslatorTest.java
@@ -1595,4 +1595,82 @@ public void setListSet(Set<List<String>> set) {}
         assertThrows(Throwable.class, () -> translateSourceFile("FailList", "FailList.m"));
     assertTrue(e.getMessage().contains("Exact converter required for mapped type"));
   }
+
+  public void testInterfaceTypes() throws IOException {
+    addSourceFile(
+        """
+        public interface TestInterface {
+        }
+        """,
+        "TestInterface.java");
+    addSourceFile(
+        """
+        import com.google.j2objc.annotations.ObjectiveCKmpMethod;
+        import java.util.Set;
+        import java.util.List;
+        public class InterfaceUsage {
+          @ObjectiveCKmpMethod(selector="getInterface", adapter=Adapter.class)
+          public TestInterface getInterface() {
+            return null;
+          }
+
+          @ObjectiveCKmpMethod(selector="setInterface:", adapter=Adapter.class)
+          public void setInterface(TestInterface value) {
+            return;
+          }
+        }
+        """,
+        "InterfaceUsage.java");
+
+    String header = translateSourceFile("InterfaceUsage", "InterfaceUsage.h");
+    assertInTranslation(
+        header,
+        """
+        - (id<TestInterface>)getInterface;
+        """);
+    assertInTranslation(
+        header,
+        """
+        - (void)setInterface:(id<TestInterface>)value;
+        """);
+  }
+
+  public void testListOfInterface() throws IOException {
+    addSourceFile(
+        """
+        public interface TestInterface {
+        }
+        """,
+        "TestInterface.java");
+    addSourceFile(
+        """
+        import com.google.j2objc.annotations.ObjectiveCKmpMethod;
+        import java.util.Set;
+        import java.util.List;
+        public class ListOfInterface {
+          @ObjectiveCKmpMethod(selector="getListOfInterface", adapter=Adapter.class)
+          public List<TestInterface> getListOfInterface() {
+            return null;
+          }
+
+          @ObjectiveCKmpMethod(selector="setListOfInterface:", adapter=Adapter.class)
+          public void setListOfInterface(List<TestInterface> list) {
+            return;
+          }
+        }
+        """,
+        "ListOfInterface.java");
+
+    String header = translateSourceFile("ListOfInterface", "ListOfInterface.h");
+    assertInTranslation(
+        header,
+        """
+        - (NSArray<id<TestInterface>> *)getListOfInterface;
+        """);
+    assertInTranslation(
+        header,
+        """
+        - (void)setListOfInterface:(NSArray<id<TestInterface>> *)list;
+        """);
+  }
 }