From 1ed22ce30a91072565020c1826b01829edb25b9f Mon Sep 17 00:00:00 2001
From: Stephan Diederich <stephan.diederich@gmail.com>
Date: Fri, 19 Dec 2025 17:27:50 +0100
Subject: [PATCH] fix duplicated fields from superclass

in case of duplicated properties, e.g. from a base class it was
generating duplicate property definitions, e.g.:

```
extension JavaClass<PrivateKey> {
  @JavaStaticField(isFinal: true)
  public var serialVersionUID: Int64

  @JavaStaticField(isFinal: true)
  public var serialVersionUID: Int64
}

```
(see e.g. https://docs.oracle.com/javase/8/docs/api/java/security/PrivateKey.html)

which then fails the swift build.

Analog to methods, this now skips the property in case it wasn't directly from
the class itself.
---
 .../JavaClassTranslator.swift                 | 13 +++---
 .../WrapJavaTests/BasicWrapJavaTests.swift    | 41 +++++++++++++++++++
 2 files changed, 48 insertions(+), 6 deletions(-)

diff --git a/Sources/SwiftJavaToolLib/JavaClassTranslator.swift b/Sources/SwiftJavaToolLib/JavaClassTranslator.swift
index f5b0b890d..94140cf64 100644
--- a/Sources/SwiftJavaToolLib/JavaClassTranslator.swift
+++ b/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)
   }
 
diff --git a/Tests/SwiftJavaToolLibTests/WrapJavaTests/BasicWrapJavaTests.swift b/Tests/SwiftJavaToolLibTests/WrapJavaTests/BasicWrapJavaTests.swift
index 74ed3ce28..3738ebf4d 100644
--- a/Tests/SwiftJavaToolLibTests/WrapJavaTests/BasicWrapJavaTests.swift
+++ b/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
+        """,
+      ]
+    )
+  }
 }
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