Merge pull request #1409 from eeight/fix_enum_corruption

Fix bug with silent message corruption in LITE_RUNTIME.

src/google/protobuf/compiler/cpp/cpp_enum_field.cc

@@ -36,6 +36,7 @@
 #include <google/protobuf/compiler/cpp/cpp_helpers.h>
 #include <google/protobuf/io/printer.h>
 #include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/wire_format.h>
 
 namespace google {
 namespace protobuf {
@@ -141,8 +142,9 @@ GenerateMergeFromCodedStream(io::Printer* printer) const {
     } else {
       printer->Print(
         "} else {\n"
-        "  unknown_fields_stream.WriteVarint32(tag);\n"
-        "  unknown_fields_stream.WriteVarint32(value);\n");
+        "  unknown_fields_stream.WriteVarint32($tag$);\n"
+        "  unknown_fields_stream.WriteVarint32(value);\n",
+        "tag", SimpleItoa(internal::WireFormat::MakeTag(descriptor_)));
     }
     printer->Print(variables_,
       "}\n");

src/google/protobuf/lite_unittest.cc

@@ -686,6 +686,33 @@ int main(int argc, char* argv[]) {
     EXPECT_TRUE(map_message.IsInitialized());
   }
 
+  {
+      // Check that adding more values to enum does not corrupt message
+      // when passed through an old client.
+      protobuf_unittest::V2MessageLite v2_message;
+      v2_message.set_int_field(800);
+      // Set enum field to the value not understood by the old client.
+      v2_message.set_enum_field(protobuf_unittest::V2_SECOND);
+      string v2_bytes = v2_message.SerializeAsString();
+
+      protobuf_unittest::V1MessageLite v1_message;
+      v1_message.ParseFromString(v2_bytes);
+      EXPECT_TRUE(v1_message.IsInitialized());
+      EXPECT_EQ(v1_message.int_field(), v2_message.int_field());
+      // V1 client does not understand V2_SECOND value, so it discards it and
+      // uses default value instead.
+      EXPECT_EQ(v1_message.enum_field(), protobuf_unittest::V1_FIRST);
+
+      // However, when re-serialized, it should preserve enum value.
+      string v1_bytes = v1_message.SerializeAsString();
+
+      protobuf_unittest::V2MessageLite same_v2_message;
+      same_v2_message.ParseFromString(v1_bytes);
+
+      EXPECT_EQ(v2_message.int_field(), same_v2_message.int_field());
+      EXPECT_EQ(v2_message.enum_field(), same_v2_message.enum_field());
+  }
+
   std::cout << "PASS" << std::endl;
   return 0;
 }

src/google/protobuf/unittest_lite.proto

@@ -386,3 +386,22 @@ message TestEmptyMessageLite{
 message TestEmptyMessageWithExtensionsLite {
   extensions 1 to max;
 }
+
+enum V1EnumLite {
+    V1_FIRST = 1;
+}
+
+enum V2EnumLite {
+    V2_FIRST = 1;
+    V2_SECOND = 2;
+}
+
+message V1MessageLite {
+    required int32 int_field = 1;
+    optional V1EnumLite enum_field = 2 [ default = V1_FIRST ];
+}
+
+message V2MessageLite {
+    required int32 int_field = 1;
+    optional V2EnumLite enum_field = 2 [ default = V2_FIRST ];
+}