fix duplicated fields from superclass (#501)

Author: diederich

Sources/SwiftJavaToolLib/JavaClassTranslator.swift

@@ -270,6 +270,13 @@ extension JavaClassTranslator {
 
   /// Add a field to the appropriate lists(s) for later translation.
   private mutating func addField(_ field: Field) {
+    // Don't include inherited fields when translating to a class.
+    // This applies to both instance and static fields to avoid duplicates
+    if translateAsClass &&
+        !field.getDeclaringClass()!.equals(javaClass.as(JavaObject.self)!) {
+      return
+    }
+
     // Static fields go into a separate list.
     if field.isStatic {
       staticFields.append(field)
@@ -283,12 +290,6 @@ extension JavaClassTranslator {
       return
     }
 
-    // Don't include inherited fields when translating to a class.
-    if translateAsClass &&
-        !field.getDeclaringClass()!.equals(javaClass.as(JavaObject.self)!) {
-      return
-    }
-
     fields.append(field)
   }
 

Tests/SwiftJavaToolLibTests/WrapJavaTests/BasicWrapJavaTests.swift

@@ -88,4 +88,45 @@ final class BasicWrapJavaTests: XCTestCase {
     )
   }
 
+
+  // Test that static fields from superclasses are not duplicated in generated code.
+  // This prevents duplicate serialVersionUID declarations when both a class and its
+  // superclass declare the field. The subclass field "hides" the superclass field,
+  // similar to how static methods work in Java.
+  func test_wrapJava_noDuplicateStaticFieldsFromSuperclass() async throws {
+    let classpathURL = try await compileJava(
+      """
+      package com.example;
+
+      class SuperClass {
+        public static final long serialVersionUID = 1L;
+      }
+
+      class SubClass extends SuperClass {
+        public static final long serialVersionUID = 2L;
+      }
+      """)
+
+    try assertWrapJavaOutput(
+      javaClassNames: [
+        "com.example.SuperClass",
+        "com.example.SubClass"
+      ],
+      classpath: [classpathURL],
+      expectedChunks: [
+        // SuperClass should have its static field
+        """
+        extension JavaClass<SuperClass> {
+        @JavaStaticField(isFinal: true)
+        public var serialVersionUID: Int64
+        """,
+        // SubClass should only have its own static field, not the superclass one
+        """
+        extension JavaClass<SubClass> {
+        @JavaStaticField(isFinal: true)
+        public var serialVersionUID: Int64
+        """,
+      ]
+    )
+  }
 }