Handle serialization of empty struct field value.

2 files changed, 16 insertions, 2 deletions

diff --git a/document/src/tests/serialization/vespadocumentserializer_test.cpp b/document/src/tests/serialization/vespadocumentserializer_test.cpp
index c12a4966bcb..f7d0cd4c3f6 100644
--- a/document/src/tests/serialization/vespadocumentserializer_test.cpp
+++ b/document/src/tests/serialization/vespadocumentserializer_test.cpp
@@ -514,6 +514,20 @@ void checkStructSerialization(const StructFieldValue &value,
     EXPECT_EQUAL(60u, element2_size);
 }
 
+TEST("requireThatEmptyStructCanBeSerialized") {
+    StructDataType structType(getStructDataType());
+    StructFieldValue value(structType);
+    nbostream stream;
+    value.reset(); // Simulate the result of deserializing empty struct
+    serializeAndDeserialize(value, stream);
+    uint32_t data_size;
+    uint8_t compression_type;
+    uint8_t field_count;
+    stream >> data_size >> compression_type >> field_count;
+    EXPECT_EQUAL(0u, data_size);
+    EXPECT_EQUAL(0u, field_count);
+}
+
 TEST("requireThatUncompressedStructFieldValueCanBeSerialized") {
     StructDataType structType(getStructDataType());
     StructFieldValue value = getStructFieldValue(structType);
diff --git a/document/src/vespa/document/serialization/vespadocumentserializer.cpp b/document/src/vespa/document/serialization/vespadocumentserializer.cpp
index a309fdd3500..28192cd6a4e 100644
--- a/document/src/vespa/document/serialization/vespadocumentserializer.cpp
+++ b/document/src/vespa/document/serialization/vespadocumentserializer.cpp
@@ -153,8 +153,8 @@ void VespaDocumentSerializer::write(const Document &value,
 
 void VespaDocumentSerializer::visit(const StructFieldValue &value)
 {
-    if (!structNeedsReserialization(value)) {
-        const StructFieldValue::Chunks & chunks = value.getChunks();
+    const StructFieldValue::Chunks & chunks = value.getChunks();
+    if (!structNeedsReserialization(value) && chunks.size() > 0) {
         assert(chunks.size() == 1);
         writeUnchanged(chunks[0]);
     } else {