Add support for moving lazy fields in static reflection message movers.

PiperOrigin-RevId: 844643215

Author: protobuf-github-bot

src/google/protobuf/extension_set.h

@@ -639,6 +639,14 @@ class PROTOBUF_EXPORT ExtensionSet {
     return extension != nullptr && extension->is_lazy;
   }
 
+  // Returns a pointer to the LazyField for the given extension number, or
+  // nullptr if the extension is not lazy.
+  // If the extension does not exist, it is created as a lazy extension.
+  // This function returns nullptr if lazy parsing is not supported, if the
+  // extension exists but is not lazy, or if the extension is not a message
+  // type.
+  LazyField* TryGetLazyField(Arena* arena, int number, FieldType type);
+
  private:
   template <typename Type>
   friend class PrimitiveTypeTraits;
@@ -742,6 +750,8 @@ class PROTOBUF_EXPORT ExtensionSet {
         io::EpsCopyOutputStream* stream) const = 0;
 
 
+    virtual LazyField* GetUnderlyingField() = 0;
+
    private:
     virtual void UnusedKeyMethod();  // Dummy key method to avoid weak vtable.
   };
@@ -1868,6 +1878,19 @@ class ExtensionIdentifier {
   typename TypeTraits::InitType default_value_;
 };
 
+template <typename ExtendeeType, typename TypeTraitsType,
+          internal::FieldType field_type, bool is_packed>
+auto TryGetLazyMessageFromExtensionSet(
+    Arena* arena,
+    const google::protobuf::internal::ExtensionIdentifier<
+        ExtendeeType, TypeTraitsType, field_type, is_packed>& extension,
+    ExtensionSet& set) {
+  static_assert(std::is_base_of_v<
+                MessageLite,
+                std::decay_t<typename TypeTraitsType::Singular::ConstType>>);
+  return set.TryGetLazyField(arena, extension.number(), field_type);
+}
+
 // -------------------------------------------------------------------
 // Generated accessors
 

src/google/protobuf/extension_set_unittest.cc

@@ -1808,6 +1808,7 @@ TEST(ExtensionSetTest, MoveExtensionWithDynamicDescriptor) {
 }
 
 
+
 TEST_P(FindExtensionTest,
        FindExtensionInfoFromFieldNumber_FindExistingExtension) {
   ExtensionInfo extension_info;

src/google/protobuf/generated_message_util.h

@@ -401,6 +401,19 @@ constexpr absl::optional<uintptr_t> EncodePlacementArenaOffsets(
 // message classes without making them public. This is useful for highly
 // optimized code paths that need to access internals.
 struct PrivateAccess {
+  template <typename T, int number>
+  static constexpr bool IsLazyField() {
+    constexpr auto l =
+        [](auto& msg) -> decltype(msg._lazy_internal_mutable(
+                          std::integral_constant<int, number>{})) {};
+    return std::is_invocable_v<decltype(l), T&>;
+  }
+
+  template <int number, typename T>
+  static auto& MutableLazy(T& msg) {
+    return msg._lazy_internal_mutable(std::integral_constant<int, number>{});
+  }
+
   template <typename T>
   static auto& GetExtensionSet(T& msg) {
     return msg._impl_._extensions_;