Extract string and bytes default value creation to a helper function

PiperOrigin-RevId: 582949483

src/google/protobuf/compiler/rust/accessors/helpers.cc

@@ -12,6 +12,7 @@
 #include <string>
 
 #include "absl/log/absl_log.h"
+#include "absl/strings/escaping.h"
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_format.h"
 #include "google/protobuf/compiler/rust/context.h"
@@ -72,12 +73,13 @@ std::string DefaultValue(Context<FieldDescriptor> field) {
     case FieldDescriptor::TYPE_BOOL:
       return absl::StrFormat("%v", field.desc().default_value_bool());
     case FieldDescriptor::TYPE_STRING:
+    case FieldDescriptor::TYPE_BYTES:
+      return absl::StrFormat(
+          "b\"%s\"", absl::CHexEscape(field.desc().default_value_string()));
     case FieldDescriptor::TYPE_GROUP:
     case FieldDescriptor::TYPE_MESSAGE:
-    case FieldDescriptor::TYPE_BYTES:
     case FieldDescriptor::TYPE_ENUM:
-      ABSL_LOG(FATAL) << "Non-singular scalar field type passed: "
-                      << field.desc().type_name();
+      ABSL_LOG(FATAL) << "Unsupported field type: " << field.desc().type_name();
   }
   ABSL_LOG(FATAL) << "unreachable";
 }

src/google/protobuf/compiler/rust/accessors/helpers.h

@@ -19,6 +19,10 @@ namespace compiler {
 namespace rust {
 
 // Returns the field's default value as a Rust literal / identifier.
+//
+// Both strings and bytes are represented as a byte string literal, i.e. in the
+// format `b"default value here"`. It is the caller's responsibility to convert
+// the byte literal to an actual string, if needed.
 std::string DefaultValue(Context<FieldDescriptor> field);
 
 }  // namespace rust

src/google/protobuf/compiler/rust/accessors/singular_string.cc

@@ -7,10 +7,10 @@
 
 #include <string>
 
-#include "absl/strings/escaping.h"
 #include "absl/strings/string_view.h"
 #include "google/protobuf/compiler/cpp/helpers.h"
 #include "google/protobuf/compiler/rust/accessors/accessor_generator.h"
+#include "google/protobuf/compiler/rust/accessors/helpers.h"
 #include "google/protobuf/compiler/rust/context.h"
 #include "google/protobuf/compiler/rust/naming.h"
 #include "google/protobuf/descriptor.h"
@@ -69,8 +69,7 @@ void SingularString::InMsgImpl(Context<FieldDescriptor> field) const {
                    {
                        {"field", field.desc().name()},
                        {"proxied_type", proxied_type},
-                       {"default_val",
-                        absl::CHexEscape(field.desc().default_value_string())},
+                       {"default_val", DefaultValue(field)},
                        {"view_type", proxied_type},
                        {"transform_field_entry",
                         [&] {
@@ -98,7 +97,7 @@ void SingularString::InMsgImpl(Context<FieldDescriptor> field) const {
                   $getter_thunk$,
                   $setter_thunk$,
                   $clearer_thunk$,
-                  b"$default_val$",
+                  $default_val$,
                 )
               };
               let out = unsafe {