From 12453371e173736190110434227b6ebe88881efa Mon Sep 17 00:00:00 2001
From: Mike Kruskal <mkruskal@google.com>
Date: Wed, 28 Sep 2022 13:22:55 -0700
Subject: [PATCH] Fixing merge issues

---
 .../com/google/protobuf/DynamicMessage.java   |  3 +-
 .../google/protobuf/MessageReflection.java    | 40 ++++++++++++++++---
 .../compiler/java/java_message_builder.cc     |  4 +-
 3 files changed, 38 insertions(+), 9 deletions(-)

diff --git a/java/core/src/main/java/com/google/protobuf/DynamicMessage.java b/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
index 76d444e61148..51e6b0c27c1f 100644
--- a/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
+++ b/java/core/src/main/java/com/google/protobuf/DynamicMessage.java
@@ -418,10 +418,11 @@ public DynamicMessage buildPartial() {
         }
       }
 
+      fields.makeImmutable();
       DynamicMessage result =
           new DynamicMessage(
               type,
-              fields.buildPartial(),
+              fields,
               java.util.Arrays.copyOf(oneofCases, oneofCases.length),
               unknownFields);
       return result;
diff --git a/java/core/src/main/java/com/google/protobuf/MessageReflection.java b/java/core/src/main/java/com/google/protobuf/MessageReflection.java
index 99615b3056e8..7cae5727afbf 100644
--- a/java/core/src/main/java/com/google/protobuf/MessageReflection.java
+++ b/java/core/src/main/java/com/google/protobuf/MessageReflection.java
@@ -378,6 +378,7 @@ MergeTarget newEmptyTargetForField(
   static class BuilderAdapter implements MergeTarget {
 
     private final Message.Builder builder;
+    private boolean hasNestedBuilders = true;
 
     @Override
     public Descriptors.Descriptor getDescriptorForType() {
@@ -393,6 +394,17 @@ public Object getField(Descriptors.FieldDescriptor field) {
       return builder.getField(field);
     }
 
+    private Message.Builder getFieldBuilder(Descriptors.FieldDescriptor field) {
+      if (hasNestedBuilders) {
+        try {
+          return builder.getFieldBuilder(field);
+        } catch (UnsupportedOperationException e) {
+          hasNestedBuilders = false;
+        }
+      }
+      return null;
+    }
+
     @Override
     public boolean hasField(Descriptors.FieldDescriptor field) {
       return builder.hasField(field);
@@ -536,11 +548,19 @@ public void mergeGroup(
         Message defaultInstance)
         throws IOException {
       if (!field.isRepeated()) {
+        Message.Builder subBuilder;
         if (hasField(field)) {
-          input.readGroup(field.getNumber(), builder.getFieldBuilder(field), extensionRegistry);
-          return;
+          subBuilder = getFieldBuilder(field);
+          if (subBuilder != null) {
+            input.readGroup(field.getNumber(), subBuilder, extensionRegistry);
+            return;
+          } else {
+            subBuilder = newMessageFieldInstance(field, defaultInstance);
+            subBuilder.mergeFrom((Message) getField(field));
+          }
+        } else {
+          subBuilder = newMessageFieldInstance(field, defaultInstance);
         }
-        Message.Builder subBuilder = newMessageFieldInstance(field, defaultInstance);
         input.readGroup(field.getNumber(), subBuilder, extensionRegistry);
         Object unused = setField(field, subBuilder.buildPartial());
       } else {
@@ -558,11 +578,19 @@ public void mergeMessage(
         Message defaultInstance)
         throws IOException {
       if (!field.isRepeated()) {
+        Message.Builder subBuilder;
         if (hasField(field)) {
-          input.readMessage(builder.getFieldBuilder(field), extensionRegistry);
-          return;
+          subBuilder = getFieldBuilder(field);
+          if (subBuilder != null) {
+            input.readMessage(subBuilder, extensionRegistry);
+            return;
+          } else {
+            subBuilder = newMessageFieldInstance(field, defaultInstance);
+            subBuilder.mergeFrom((Message) getField(field));
+          }
+        } else {
+          subBuilder = newMessageFieldInstance(field, defaultInstance);
         }
-        Message.Builder subBuilder = newMessageFieldInstance(field, defaultInstance);
         input.readMessage(subBuilder, extensionRegistry);
         Object unused = setField(field, subBuilder.buildPartial());
       } else {
diff --git a/src/google/protobuf/compiler/java/java_message_builder.cc b/src/google/protobuf/compiler/java/java_message_builder.cc
index 72adc52d75ed..24ea648c79f3 100644
--- a/src/google/protobuf/compiler/java/java_message_builder.cc
+++ b/src/google/protobuf/compiler/java/java_message_builder.cc
@@ -673,7 +673,7 @@ void MessageBuilderGenerator::GenerateBuilderFieldParsingCase(
     io::Printer* printer, const FieldDescriptor* field) {
   uint32_t tag = WireFormatLite::MakeTag(
       field->number(), WireFormat::WireTypeForFieldType(field->type()));
-  std::string tagString = absl::StrCat(static_cast<int32_t>(tag));
+  std::string tagString = StrCat(static_cast<int32_t>(tag));
   printer->Print("case $tag$: {\n", "tag", tagString);
   printer->Indent();
 
@@ -692,7 +692,7 @@ void MessageBuilderGenerator::GenerateBuilderPackedFieldParsingCase(
   // packed version of this field regardless of field->options().packed().
   uint32_t tag = WireFormatLite::MakeTag(
       field->number(), WireFormatLite::WIRETYPE_LENGTH_DELIMITED);
-  std::string tagString = absl::StrCat(static_cast<int32_t>(tag));
+  std::string tagString = StrCat(static_cast<int32_t>(tag));
   printer->Print("case $tag$: {\n", "tag", tagString);
   printer->Indent();