1 files changed, 17 insertions, 0 deletions
diff --git a/java/core/src/test/java/com/google/protobuf/LazyMessageLiteTest.java b/java/core/src/test/java/com/google/protobuf/LazyMessageLiteTest.java
index afe0fffd..e5b11cf1 100644
--- a/java/core/src/test/java/com/google/protobuf/LazyMessageLiteTest.java
+++ b/java/core/src/test/java/com/google/protobuf/LazyMessageLiteTest.java
@@ -251,6 +251,23 @@ public class LazyMessageLiteTest extends TestCase {
     assertEquals(42, merged.getOneofInner().getNumWithDefault());
   }
 
+  // Regression test for b/28198805.
+  public void testMergeOneofMessages() throws Exception {
+    LazyInnerMessageLite inner = LazyInnerMessageLite.newBuilder().build();
+    LazyMessageLite outer = LazyMessageLite.newBuilder().setOneofInner(inner).build();
+    ByteString data1 = outer.toByteString();
+
+    // The following should not alter the content of the 'outer' message.
+    LazyMessageLite.Builder merged = LazyMessageLite.newBuilder().mergeFrom(outer);
+    LazyInnerMessageLite anotherInner = LazyInnerMessageLite.newBuilder().setNum(12345).build();
+    merged.setOneofInner(anotherInner);
+
+    // Check that the 'outer' stays the same.
+    ByteString data2 = outer.toByteString();
+    assertEquals(data1, data2);
+    assertEquals(0, outer.getOneofInner().getNum());
+  }
+
   public void testSerialize() throws InvalidProtocolBufferException {
     LazyNestedInnerMessageLite nested = LazyNestedInnerMessageLite.newBuilder()
         .setNum(3)