Merge pull request #17789 from protocolbuffers/cp-string-type

Introduce FieldDescriptor::cpp_string_type() API to replace direct ct…

Author: zhangskz

src/google/protobuf/descriptor.cc

@@ -3941,6 +3941,29 @@ bool FieldDescriptor::has_optional_keyword() const {
                               is_optional() && !containing_oneof());
 }
 
+FieldDescriptor::CppStringType FieldDescriptor::cpp_string_type() const {
+  ABSL_DCHECK(cpp_type() == FieldDescriptor::CPPTYPE_STRING);
+  switch (features().GetExtension(pb::cpp).string_type()) {
+    case pb::CppFeatures::VIEW:
+      return CppStringType::kView;
+    case pb::CppFeatures::CORD:
+      // In open-source, protobuf CORD is only supported for singular bytes
+      // fields.
+      if (type() != FieldDescriptor::TYPE_BYTES || is_repeated() ||
+          is_extension()) {
+        return CppStringType::kString;
+      }
+      return CppStringType::kCord;
+    case pb::CppFeatures::STRING:
+      return CppStringType::kString;
+    default:
+      // If features haven't been resolved, this is a dynamic build not for C++
+      // codegen.  Just use string type.
+      ABSL_DCHECK(!features().GetExtension(pb::cpp).has_string_type());
+      return CppStringType::kString;
+  }
+}
+
 // Location methods ===============================================
 
 bool FileDescriptor::GetSourceLocation(const std::vector<int>& path,

src/google/protobuf/descriptor.h

@@ -859,6 +859,10 @@ class PROTOBUF_EXPORT FieldDescriptor : private internal::SymbolBase,
   const char* cpp_type_name() const;  // Name of the C++ type.
   Label label() const;                // optional/required/repeated
 
+#ifndef SWIG
+  CppStringType cpp_string_type() const;  // The C++ string type of this field.
+#endif
+
   bool is_required() const;  // shorthand for label() == LABEL_REQUIRED
   bool is_optional() const;  // shorthand for label() == LABEL_OPTIONAL
   bool is_repeated() const;  // shorthand for label() == LABEL_REPEATED
@@ -2892,22 +2896,21 @@ PROTOBUF_EXPORT bool HasPreservingUnknownEnumSemantics(
 
 PROTOBUF_EXPORT bool HasHasbit(const FieldDescriptor* field);
 
+#ifndef SWIG
 // For a string field, returns the effective ctype.  If the actual ctype is
 // not supported, returns the default of STRING.
 template <typename FieldDesc = FieldDescriptor,
           typename FieldOpts = FieldOptions>
 typename FieldOpts::CType EffectiveStringCType(const FieldDesc* field) {
-  ABSL_DCHECK(field->cpp_type() == FieldDescriptor::CPPTYPE_STRING);
-  // Open-source protobuf release only supports STRING ctype and CORD for
-  // sinuglar bytes.
-  if (field->type() == FieldDescriptor::TYPE_BYTES && !field->is_repeated() &&
-      field->options().ctype() == FieldOpts::CORD && !field->is_extension()) {
-    return FieldOpts::CORD;
+  // TODO Replace this function with FieldDescriptor::string_type;
+  switch (field->cpp_string_type()) {
+    case FieldDescriptor::CppStringType::kCord:
+      return FieldOpts::CORD;
+    default:
+      return FieldOpts::STRING;
   }
-  return FieldOpts::STRING;
 }
 
-#ifndef SWIG
 enum class Utf8CheckMode : uint8_t {
   kStrict = 0,  // Parsing will fail if non UTF-8 data is in string fields.
   kVerify = 1,  // Only log an error but parsing will succeed.

src/google/protobuf/descriptor_lite.h

@@ -78,6 +78,17 @@ class FieldDescriptorLite {
     MAX_LABEL = 3,  // Constant useful for defining lookup tables
                     // indexed by Label.
   };
+
+  // Identifies the storage type of a C++ string field.  This corresponds to
+  // pb.CppFeatures.StringType, but is compatible with ctype prior to Edition
+  // 2024.  0 is reserved for errors.
+#ifndef SWIG
+  enum class CppStringType {
+    kView = 1,
+    kCord = 2,
+    kString = 3,
+  };
+#endif
 };
 
 }  // namespace internal

src/google/protobuf/descriptor_unittest.cc

@@ -7593,6 +7593,9 @@ TEST_F(FeaturesTest, Proto2Features) {
   EXPECT_TRUE(message->FindFieldByName("req")->is_required());
   EXPECT_TRUE(file->enum_type(0)->is_closed());
 
+  EXPECT_EQ(message->FindFieldByName("str")->cpp_string_type(),
+            FieldDescriptor::CppStringType::kString);
+
   // Check round-trip consistency.
   FileDescriptorProto proto;
   file->CopyTo(&proto);
@@ -9709,6 +9712,73 @@ TEST_F(FeaturesTest, EnumFeatureHelpers) {
   EXPECT_FALSE(HasPreservingUnknownEnumSemantics(field_legacy_closed));
 }
 
+TEST_F(FeaturesTest, FieldCppStringType) {
+  BuildDescriptorMessagesInTestPool();
+  const std::string file_contents = absl::Substitute(
+      R"pb(
+        name: "foo.proto"
+        syntax: "editions"
+        edition: EDITION_2024
+        message_type {
+          name: "Foo"
+          field {
+            name: "view"
+            number: 1
+            label: LABEL_OPTIONAL
+            type: TYPE_STRING
+          }
+          field {
+            name: "str"
+            number: 2
+            label: LABEL_OPTIONAL
+            type: TYPE_STRING
+            options {
+              features {
+                [pb.cpp] { string_type: STRING }
+              }
+            }
+          }
+          field {
+            name: "cord"
+            number: 3
+            label: LABEL_OPTIONAL
+            type: TYPE_STRING
+            options {
+              features {
+                [pb.cpp] { string_type: CORD }
+              }
+            }
+          }
+          field {
+            name: "cord_bytes"
+            number: 4
+            label: LABEL_OPTIONAL
+            type: TYPE_BYTES
+            options {
+              features {
+                [pb.cpp] { string_type: CORD }
+              }
+            }
+          } $0
+        }
+      )pb",
+      ""
+  );
+  const FileDescriptor* file = BuildFile(file_contents);
+  const Descriptor* message = file->message_type(0);
+  const FieldDescriptor* view = message->field(0);
+  const FieldDescriptor* str = message->field(1);
+  const FieldDescriptor* cord = message->field(2);
+  const FieldDescriptor* cord_bytes = message->field(3);
+
+  EXPECT_EQ(view->cpp_string_type(), FieldDescriptor::CppStringType::kView);
+  EXPECT_EQ(str->cpp_string_type(), FieldDescriptor::CppStringType::kString);
+  EXPECT_EQ(cord_bytes->cpp_string_type(),
+            FieldDescriptor::CppStringType::kCord);
+  EXPECT_EQ(cord->cpp_string_type(), FieldDescriptor::CppStringType::kString);
+
+}
+
 TEST_F(FeaturesTest, MergeFeatureValidationFailed) {
   BuildDescriptorMessagesInTestPool();
   BuildFileInTestPool(pb::TestFeatures::descriptor()->file());