Add missing test to verify that LookupMapValue sync's the repeated field data

before doing the lookup in the map.

PiperOrigin-RevId: 704714248

src/google/protobuf/map_test.inc

@@ -1387,6 +1387,45 @@ TEST_P(MapTestWithParams, SwapMapsFieldsViaReflection) {
   reflection_tester.ExpectMapFieldsSetViaReflectionIterator(rhs);
 }
 
+class MapTestCodegenOrDynamic : public testing::TestWithParam<bool> {};
+
+INSTANTIATE_TEST_SUITE_P(MapTestCodegenOrDynamicSuite, MapTestCodegenOrDynamic,
+                         testing::Bool());
+
+TEST_P(MapTestCodegenOrDynamic, LookupMapValueSyncsRepeatedFieldRep) {
+  auto* descriptor = UNITTEST::TestMap::descriptor();
+  bool use_dynamic = GetParam();
+
+  DynamicMessageFactory factory;
+  std::unique_ptr<Message> dyn_message(
+      factory.GetPrototype(descriptor)->New());
+  TestMap gen_message;
+  Message* msg = use_dynamic ? dyn_message.get() : &gen_message;
+
+  const auto* reflection = msg->GetReflection();
+  const auto* field = msg->GetDescriptor()->FindFieldByName("map_int32_int32");
+
+  MapKey map_key;
+  map_key.SetInt32Value(10);
+  auto res =
+      MapReflectionTester::LookupMapValue(*reflection, *msg, *field, map_key);
+  // Check that we don't have it yet.
+  ASSERT_FALSE(res.has_value());
+
+  {
+    auto* sub = reflection->AddMessage(msg, field);
+    sub->GetReflection()->SetInt32(sub, sub->GetDescriptor()->map_key(), 10);
+    sub->GetReflection()->SetInt32(sub, sub->GetDescriptor()->map_value(), 100);
+  }
+
+
+  res = MapReflectionTester::LookupMapValue(*reflection, *msg, *field, map_key);
+  // If this fails, LookupMapValue might have failed to sync from the repeated
+  // field.
+  ASSERT_TRUE(res.has_value());
+  EXPECT_EQ(res->GetInt32Value(), 100);
+}
+
 TEST_F(MapImplTest, SpaceUsed) {
   constexpr size_t kMinCap = 16 / sizeof(void*);
 

src/google/protobuf/reflection_tester.h

@@ -8,6 +8,8 @@
 #ifndef GOOGLE_PROTOBUF_REFLECTION_TESTER_H__
 #define GOOGLE_PROTOBUF_REFLECTION_TESTER_H__
 
+#include <optional>
+
 #include "google/protobuf/map_field.h"
 #include "google/protobuf/message.h"
 
@@ -49,13 +51,15 @@ class MapReflectionTester {
   MapIterator MapEnd(Message* message, const std::string& field_name);
   int MapSize(const Message& message, const std::string& field_name);
 
-  static MapValueConstRef LookupMapValue(const Reflection& reflection,
-                                         const Message& message,
-                                         const FieldDescriptor& descriptor,
-                                         const MapKey& map_key) {
+  static std::optional<MapValueConstRef> LookupMapValue(
+      const Reflection& reflection, const Message& message,
+      const FieldDescriptor& descriptor, const MapKey& map_key) {
     MapValueConstRef map_val_const;
-    reflection.LookupMapValue(message, &descriptor, map_key, &map_val_const);
-    return map_val_const;
+    if (reflection.LookupMapValue(message, &descriptor, map_key,
+                                  &map_val_const)) {
+      return map_val_const;
+    }
+    return std::nullopt;
   }
 
   static std::string long_string() {