Internal change

PiperOrigin-RevId: 897682871

Author: protobuf-github-bot

csharp/Google.Protobuf.Tools.nuspec

@@ -23,8 +23,8 @@
     <file src="protoc/linux_aarch64/protoc" target="tools/linux_aarch64/protoc"/>
     <file src="protoc/macosx_x64/protoc" target="tools/macosx_x64/protoc"/>
     <!--
-      - Include the protos for the well-known types in a directory where protoc will
-      - find them by default.
+      - Include the protos for the well-known types and language-specific editions features in a
+      - directory where protoc will find them by default.
       -->
     <file src="src/google/protobuf/any.proto" target="tools/include/google/protobuf"/>
     <file src="src/google/protobuf/api.proto" target="tools/include/google/protobuf"/>
@@ -37,9 +37,11 @@
     <file src="src/google/protobuf/timestamp.proto" target="tools/include/google/protobuf"/>
     <file src="src/google/protobuf/type.proto" target="tools/include/google/protobuf"/>
     <file src="src/google/protobuf/wrappers.proto" target="tools/include/google/protobuf"/>
+    <file src="csharp/google/protobuf/c_sharp_features.proto" target="tools/include/google/protobuf"/>
     <!--
       - Include the protos for the well-known types again in their old location,
-      - for backward compatibility.
+      - for backward compatibility. This does not include features files, as those have never been
+      - in tools/google/protobuf directory.
       -->
     <file src="src/google/protobuf/any.proto" target="tools/google/protobuf"/>
     <file src="src/google/protobuf/api.proto" target="tools/google/protobuf"/>

csharp/generate_protos.sh

@@ -67,6 +67,7 @@ $PROTOC -Isrc -I. -Ijava/core/src/main/resources/ \
     conformance/test_protos/test_messages_edition2023.proto \
     conformance/test_protos/test_messages_edition_unstable.proto \
     csharp/protos/map_unittest_proto3.proto \
+    csharp/protos/nrt.proto \
     csharp/protos/unittest_issues.proto \
     csharp/protos/unittest_custom_options_proto3.proto \
     csharp/protos/unittest_proto3.proto \

csharp/google/protobuf/c_sharp_features.proto

@@ -20,4 +20,17 @@ extend google.protobuf.FeatureSet {
 }
 
 message CSharpFeatures {
+  // Whether the generated files should have nullable reference type annotations.
+  // When enabled, the generated C# code includes `#nullable enable annotations`
+  // and annotates message-typed properties and certain parameters with `?`.
+  optional bool nullable_reference_types = 1 [
+    retention = RETENTION_RUNTIME,
+    targets = TARGET_TYPE_FIELD,
+    targets = TARGET_TYPE_MESSAGE,
+    targets = TARGET_TYPE_FILE,
+    feature_support = {
+      edition_introduced: EDITION_UNSTABLE,
+    },
+    edition_defaults = { edition: EDITION_LEGACY, value: "false" }
+  ];
 }

csharp/protos/nrt.proto

@@ -0,0 +1,41 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2026 Google Inc.  All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file or at
+// https://developers.google.com/open-source/licenses/bsd
+
+edition = "UNSTABLE";
+
+package protobuf_editionstesting;
+
+import "csharp/protos/unittest_import_proto3.proto";
+
+import option "csharp/google/protobuf/c_sharp_features.proto";
+option features.(pb.csharp).nullable_reference_types = true;
+option csharp_namespace = "Google.Protobuf.TestProtos";
+
+// This file is used for testing NRT support in C#, both in terms of
+// manual inspection of the generated code, and checking that it compiles.
+// It exercises many aspects of protobuf, but does not attempt to be
+// comprehensive in checking (for example) all primitive numeric types.
+
+message NrtMessage {
+
+  protobuf_unittest_import.ImportMessage proto3_import_message = 1;
+  OtherNrtMessage other_message = 2;
+
+  message NestedMessage {
+    string text = 1;
+  }
+}
+
+message OtherNrtMessage {
+  string text = 1;
+}
+
+enum NrtEnum {
+  NRT_ENUM_UNSPECIFIED = 0;
+  FOO = 1;
+  BAR = 2;
+}

src/google/protobuf/compiler/csharp/csharp_field_base.cc

@@ -14,6 +14,7 @@
 
 #include "absl/log/absl_log.h"
 #include "google/protobuf/compiler/code_generator.h"
+#include "google/protobuf/compiler/csharp/csharp_generator.h"
 #include "google/protobuf/compiler/csharp/csharp_helpers.h"
 #include "google/protobuf/compiler/csharp/names.h"
 #include "google/protobuf/descriptor.h"
@@ -115,6 +116,9 @@ void FieldGeneratorBase::SetCommonFieldVariables(
                        absl::StrCat("other.", (*variables)["property_name"],
                                     " != ", (*variables)["default_value"])});
   }
+  // This isn't valid everywhere, but we assume that the code which uses
+  // the variable will only do so in a context where the annotation is valid.
+  (*variables)["nrt_annotation"] = nrt_enabled_ ? "?" : "";
 }
 
 void FieldGeneratorBase::SetCommonOneofFieldVariables(
@@ -129,13 +133,19 @@ void FieldGeneratorBase::SetCommonOneofFieldVariables(
   }
   (*variables)["oneof_case_name"] = oneof_case_name();
   (*variables)["oneof_property_name"] = oneof_property_name();
+  // This isn't valid everywhere, but we assume that the code which uses
+  // the variable will only do so in a context where the annotation is valid.
+  (*variables)["nrt_annotation"] = nrt_enabled_ ? "?" : "";
 }
 
 FieldGeneratorBase::FieldGeneratorBase(const FieldDescriptor* descriptor,
                                        int presenceIndex, const Options* options)
     : SourceGeneratorBase(options),
       descriptor_(descriptor),
       presenceIndex_(presenceIndex) {
+  nrt_enabled_ = Generator::GetResolvedSourceFeatures(*descriptor->file())
+                     .GetExtension(pb::csharp)
+                     .nullable_reference_types();
   SetCommonFieldVariables(&variables_);
 }
 
@@ -216,10 +226,12 @@ std::string FieldGeneratorBase::type_name(const FieldDescriptor* descriptor) {
         const FieldDescriptor* wrapped_field =
             descriptor->message_type()->field(0);
         std::string wrapped_field_type_name = type_name(wrapped_field);
-        // String and ByteString go to the same type; other wrapped types
-        // go to the nullable equivalent.
-        if (wrapped_field->type() == FieldDescriptor::TYPE_STRING ||
-            wrapped_field->type() == FieldDescriptor::TYPE_BYTES) {
+        // String and ByteString go to the same type (unless nullable reference
+        // type is supported for this field); other wrapped types go to the
+        // nullable equivalent.
+        if (!nrt_enabled_ &&
+            (wrapped_field->type() == FieldDescriptor::TYPE_STRING ||
+             wrapped_field->type() == FieldDescriptor::TYPE_BYTES)) {
           return wrapped_field_type_name;
         } else {
           return absl::StrCat(wrapped_field_type_name, "?");

src/google/protobuf/compiler/csharp/csharp_field_base.h

@@ -55,6 +55,8 @@ class FieldGeneratorBase : public SourceGeneratorBase {
  protected:
   const FieldDescriptor* descriptor_;
   const int presenceIndex_;
+  // NRT = Nullable Reference Types
+  bool nrt_enabled_;
   absl::flat_hash_map<absl::string_view, std::string> variables_;
 
   void AddDeprecatedFlag(io::Printer* printer);

src/google/protobuf/compiler/csharp/csharp_generator.h

@@ -11,8 +11,10 @@
 #define GOOGLE_PROTOBUF_COMPILER_CSHARP_CSHARP_GENERATOR_H__
 
 #include <string>
+#include <vector>
 
 #include "google/protobuf/compiler/code_generator.h"
+#include "google/protobuf/csharp/google/protobuf/c_sharp_features.pb.h"
 #include "google/protobuf/port_def.inc"
 
 namespace google {
@@ -37,6 +39,11 @@ class PROTOC_EXPORT Generator : public CodeGenerator {
   Edition GetMinimumEdition() const override { return Edition::EDITION_PROTO2; }
   Edition GetMaximumEdition() const override { return Edition::EDITION_2024; }
   using CodeGenerator::GetEdition;
+
+  std::vector<const FieldDescriptor*> GetFeatureExtensions() const override {
+    return {GetExtensionReflection(pb::csharp)};
+  }
+  using CodeGenerator::GetResolvedSourceFeatures;
 };
 
 }  // namespace csharp

src/google/protobuf/compiler/csharp/csharp_message.cc

@@ -18,6 +18,7 @@
 #include "google/protobuf/compiler/csharp/csharp_doc_comment.h"
 #include "google/protobuf/compiler/csharp/csharp_enum.h"
 #include "google/protobuf/compiler/csharp/csharp_field_base.h"
+#include "google/protobuf/compiler/csharp/csharp_generator.h"
 #include "google/protobuf/compiler/csharp/csharp_helpers.h"
 #include "google/protobuf/compiler/csharp/csharp_options.h"
 #include "google/protobuf/compiler/csharp/names.h"
@@ -60,6 +61,9 @@ MessageGenerator::MessageGenerator(const Descriptor* descriptor,
     }
   }
   has_bit_field_count_ = (presence_bit_count + 31) / 32;
+  nrt_enabled_ = Generator::GetResolvedSourceFeatures(*descriptor->file())
+                     .GetExtension(pb::csharp)
+                     .nullable_reference_types();
 }
 
 MessageGenerator::~MessageGenerator() = default;
@@ -93,6 +97,7 @@ void MessageGenerator::Generate(io::Printer* printer) {
   absl::flat_hash_map<absl::string_view, std::string> vars;
   vars["class_name"] = class_name();
   vars["access_level"] = class_access_level();
+  vars["nrt_annotation"] = nrt_enabled_ ? "?" : "";
 
   WriteMessageDocComment(printer, options(), descriptor_);
   AddDeprecatedFlag(printer);
@@ -120,7 +125,8 @@ void MessageGenerator::Generate(io::Printer* printer) {
       "private static readonly pb::MessageParser<$class_name$> _parser = new "
       "pb::MessageParser<$class_name$>(() => new $class_name$());\n");
 
-  printer->Print("private pb::UnknownFieldSet _unknownFields;\n");
+  printer->Print(
+      vars, "private pb::UnknownFieldSet$nrt_annotation$ _unknownFields;\n");
 
   if (has_extension_ranges_) {
     if (IsDescriptorProto(descriptor_->file())) {
@@ -256,7 +262,7 @@ void MessageGenerator::Generate(io::Printer* printer) {
         "TValue> extension) {\n"
         "  return pb::ExtensionSet.Get(ref _extensions, extension);\n"
         "}\n"
-        "public pbc::RepeatedField<TValue> "
+        "public pbc::RepeatedField<TValue>$nrt_annotation$ "
         "GetExtension<TValue>(pb::RepeatedExtension<$class_name$, TValue> "
         "extension) {\n"
         "  return pb::ExtensionSet.Get(ref _extensions, extension);\n"
@@ -314,6 +320,7 @@ void MessageGenerator::Generate(io::Printer* printer) {
         "\n");
   }
 
+  // FIXME
   if (descriptor_->extension_count() > 0) {
     printer->Print(vars,
                    "#region Extensions\n"
@@ -417,16 +424,17 @@ void MessageGenerator::GenerateFreezingCode(io::Printer* printer) {}
 void MessageGenerator::GenerateFrameworkMethods(io::Printer* printer) {
   absl::flat_hash_map<absl::string_view, std::string> vars;
   vars["class_name"] = class_name();
+  vars["nrt_annotation"] = nrt_enabled_ ? "?" : "";
 
   // Equality
   WriteGeneratedCodeAttributes(printer);
   printer->Print(vars,
-                 "public override bool Equals(object other) {\n"
+                 "public override bool Equals(object$nrt_annotation$ other) {\n"
                  "  return Equals(other as $class_name$);\n"
                  "}\n\n");
   WriteGeneratedCodeAttributes(printer);
   printer->Print(vars,
-                 "public bool Equals($class_name$ other) {\n"
+                 "public bool Equals($class_name$$nrt_annotation$ other) {\n"
                  "  if (ReferenceEquals(other, null)) {\n"
                  "    return false;\n"
                  "  }\n"

src/google/protobuf/compiler/csharp/csharp_message.h

@@ -40,6 +40,8 @@ class MessageGenerator : public SourceGeneratorBase {
   std::vector<const FieldDescriptor*> fields_by_number_;
   int has_bit_field_count_;
   bool has_extension_ranges_;
+  // NRT = Nullable Reference Types
+  bool nrt_enabled_;
 
   void GenerateMessageSerializationMethods(io::Printer* printer);
   void GenerateWriteToBody(io::Printer* printer, bool use_write_context);

src/google/protobuf/compiler/csharp/csharp_message_field.cc

@@ -35,19 +35,17 @@ MessageFieldGenerator::MessageFieldGenerator(const FieldDescriptor* descriptor,
 MessageFieldGenerator::~MessageFieldGenerator() = default;
 
 void MessageFieldGenerator::GenerateMembers(io::Printer* printer) {
-  printer->Print(
-    variables_,
-    "private $type_name$ $name$_;\n");
+  printer->Print(variables_, "private $type_name$$nrt_annotation$ $name$_;\n");
   WritePropertyDocComment(printer, options(), descriptor_);
   AddPublicMemberAttributes(printer);
   printer->Print(
-    variables_,
-    "$access_level$ $type_name$ $property_name$ {\n"
-    "  get { return $name$_; }\n"
-    "  set {\n"
-    "    $name$_ = value;\n"
-    "  }\n"
-    "}\n");
+      variables_,
+      "$access_level$ $type_name$$nrt_annotation$ $property_name$ {\n"
+      "  get { return $name$_; }\n"
+      "  set {\n"
+      "    $name$_ = value;\n"
+      "  }\n"
+      "}\n");
   if (SupportsPresenceApi(descriptor_)) {
     printer->Print(
       variables_,
@@ -189,14 +187,17 @@ void MessageOneofFieldGenerator::GenerateMembers(io::Printer* printer) {
   WritePropertyDocComment(printer, options(), descriptor_);
   AddPublicMemberAttributes(printer);
   printer->Print(
-    variables_,
-    "$access_level$ $type_name$ $property_name$ {\n"
-    "  get { return $has_property_check$ ? ($type_name$) $oneof_name$_ : null; }\n"
-    "  set {\n"
-    "    $oneof_name$_ = value;\n"
-    "    $oneof_name$Case_ = value == null ? $oneof_property_name$OneofCase.None : $oneof_property_name$OneofCase.$oneof_case_name$;\n"
-    "  }\n"
-    "}\n");
+      variables_,
+      "$access_level$ $type_name$$nrt_annotation$ $property_name$ {\n"
+      "  get { return $has_property_check$ ? ($type_name$) $oneof_name$_ : "
+      "null; }\n"
+      "  set {\n"
+      "    $oneof_name$_ = value;\n"
+      "    $oneof_name$Case_ = value == null ? "
+      "$oneof_property_name$OneofCase.None : "
+      "$oneof_property_name$OneofCase.$oneof_case_name$;\n"
+      "  }\n"
+      "}\n");
   if (SupportsPresenceApi(descriptor_)) {
     printer->Print(
       variables_,