Fix Issue 136: the memoized serialized size for packed fields may not

be properly set. writeTo() may be invoked without a call to
getSerializedSize(), so the generated serialization methods would
write a length of 0 for non-empty packed fields. Just call
getSerializedSize() at the beginning of writeTo(): although this
means that we may compute the byte size needlessly when there
are no packed fields, in practice, getSerializedSize() will
already have been called - all of the writeTo() wrappers in
AbstractMessageLite invoke it.

Tested: new unittest case in WireFormatTest.java now passes

java/src/test/java/com/google/protobuf/WireFormatTest.java

@@ -102,6 +102,28 @@ public class WireFormatTest extends TestCase {
     assertEquals(rawBytes, rawBytes2);
   }
 
+  public void testSerializationPackedWithoutGetSerializedSize()
+      throws Exception {
+    // Write directly to an OutputStream, without invoking getSerializedSize()
+    // This used to be a bug where the size of a packed field was incorrect,
+    // since getSerializedSize() was never invoked.
+    TestPackedTypes message = TestUtil.getPackedSet();
+
+    // Directly construct a CodedOutputStream around the actual OutputStream,
+    // in case writeTo(OutputStream output) invokes getSerializedSize();
+    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+    CodedOutputStream codedOutput = CodedOutputStream.newInstance(outputStream);
+
+    message.writeTo(codedOutput);
+
+    codedOutput.flush();
+
+    TestPackedTypes message2 = TestPackedTypes.parseFrom(
+        outputStream.toByteArray());
+
+    TestUtil.assertPackedFieldsSet(message2);
+  }
+
   public void testSerializeExtensionsLite() throws Exception {
     // TestAllTypes and TestAllExtensions should have compatible wire formats,
     // so if we serialize a TestAllExtensions then parse it as TestAllTypes

src/google/protobuf/compiler/java/java_message.cc

@@ -394,6 +394,14 @@ GenerateMessageSerializationMethods(io::Printer* printer) {
     "public void writeTo(com.google.protobuf.CodedOutputStream output)\n"
     "                    throws java.io.IOException {\n");
   printer->Indent();
+  // writeTo(CodedOutputStream output) might be invoked without
+  // getSerializedSize() ever being called, but we need the memoized
+  // sizes in case this message has packed fields. Rather than emit checks for
+  // each packed field, just call getSerializedSize() up front for all messages.
+  // In most cases, getSerializedSize() will have already been called anyway by
+  // one of the wrapper writeTo() methods, making this call cheap.
+  printer->Print(
+    "getSerializedSize();\n");
 
   if (descriptor_->extension_range_count() > 0) {
     if (descriptor_->options().message_set_wire_format()) {

src/google/protobuf/compiler/java/java_primitive_field.cc

@@ -298,7 +298,7 @@ GenerateMembers(io::Printer* printer) const {
   if (descriptor_->options().packed() &&
       HasGeneratedMethods(descriptor_->containing_type())) {
     printer->Print(variables_,
-      "private int $name$MemoizedSerializedSize;\n");
+      "private int $name$MemoizedSerializedSize = -1;\n");
   }
 }