Implement AbslStringify for MessageLite

PiperOrigin-RevId: 499547257

src/google/protobuf/lite_unittest.cc

@@ -39,6 +39,7 @@
 #include <gtest/gtest.h>
 #include "google/protobuf/stubs/logging.h"
 #include "absl/strings/match.h"
+#include "absl/strings/str_cat.h"
 #include "absl/strings/string_view.h"
 #include "google/protobuf/arena_test_util.h"
 #include "google/protobuf/io/coded_stream.h"
@@ -1171,6 +1172,7 @@ TYPED_TEST(LiteTest, DebugString) {
   EXPECT_NE(message1.DebugString(), message2.DebugString());
 }
 
+
 TYPED_TEST(LiteTest, EnumValueToName) {
   EXPECT_EQ("FOREIGN_LITE_FOO", protobuf_unittest::ForeignEnumLite_Name(
                                     protobuf_unittest::FOREIGN_LITE_FOO));

src/google/protobuf/message_lite.h

@@ -222,6 +222,13 @@ class PROTOBUF_EXPORT MessageLite {
   // with Message.
   std::string Utf8DebugString() const { return DebugString(); }
 
+  // Implementation of the `AbslStringify` interface. This adds `DebugString()`
+  // to the sink. Do not rely on exact format.
+  template <typename Sink>
+  friend void AbslStringify(Sink& sink, const google::protobuf::MessageLite& msg) {
+    sink.Append(msg.DebugString());
+  }
+
   // Parsing ---------------------------------------------------------
   // Methods for parsing in protocol buffer format.  Most of these are
   // just simple wrappers around MergeFromCodedStream().  Clear() will be