[protobuf] How to resolve a custom option in a protocol buffer FileDescriptor

[Bill Smith]

I'm using protocol buffers 2.5 with Java. I have a proto file that defines 
a custom option. Another proto file uses that custom option. If I persist 
the corresponding FileDescriptorProto's and then read them and convert them 
to FileDescriptors, the reference to the custom option is manifested as 
unknown field. How do I cause that custom option to be resolved correctly?

Here's the code. I have two .proto files. protobuf-options.proto looks like 
this:

package options;
import "google/protobuf/descriptor.proto";

option java_package = "com.example.proto";
option java_outer_classname = "Options";

extend google.protobuf.FieldOptions {
optional bool scrub = 5;}

The imported google/protobuf/descriptor.proto is exactly the 
descriptor.proto that ships with Protocol Buffers 2.5.

example.proto looks like this:

package example;
option java_package = "com.example.protos";
option java_outer_classname = "ExampleProtos";
option optimize_for = SPEED;
option java_generic_services = false;
import "protobuf-options.proto";

message M {
optional int32 field1 = 1;
optional string field2 = 2 [(options.scrub) = true];}

As you can see, field2 references the custom option defined by 
protobuf-options.proto.

The following code writes a binary-encoded version of all three protos to 
/tmp:

package com.example;
import com.google.protobuf.ByteString;import 
com.google.protobuf.DescriptorProtos.FileDescriptorProto;import 
com.google.protobuf.Descriptors.FileDescriptor;import 
com.example.protos.ExampleProtos;
import java.io.FileOutputStream;import java.io.OutputStream;
/**
 *
 */public class PersistFDs {
public void persist(final FileDescriptor fileDescriptor) throws Exception {
System.out.println("persisting "+fileDescriptor.getName());
try (final OutputStream outputStream = new 
FileOutputStream("/tmp/"+fileDescriptor.getName())) {
final FileDescriptorProto fileDescriptorProto = 
fileDescriptor.toProto();
final ByteString byteString = fileDescriptorProto.toByteString();
byteString.writeTo(outputStream);
}
for (final FileDescriptor dependency : 
fileDescriptor.getDependencies()) {
persist(dependency);
}
}
public static void main(String[] args) throws Exception {
final PersistFDs self = new PersistFDs();
self.persist(ExampleProtos.getDescriptor());
}}

Finally, the following code loads those those protos from /tmp, converts 
them back into FileDescriptors, and then checks for the custom option on 
field2:

package com.example;
import com.google.protobuf.ByteString;import 
com.google.protobuf.DescriptorProtos.FileDescriptorProto;import 
com.google.protobuf.Descriptors.FieldDescriptor;import 
com.google.protobuf.Descriptors.FileDescriptor;import 
com.google.protobuf.UnknownFieldSet.Field;
import java.io.FileInputStream;import java.io.InputStream;
/**
 *
 */public class LoadFDs {
public FileDescriptorProto loadProto(final String filePath) throws 
Exception {
try (final InputStream inputStream = new FileInputStream(filePath)) {
final ByteString byteString = ByteString.readFrom(inputStream);
final FileDescriptorProto result = 
FileDescriptorProto.parseFrom(byteString);

return result;
}
}

public static void main(final String[] args) throws Exception {
final LoadFDs self = new LoadFDs();

final FileDescriptorProto descriptorFDProto = 
self.loadProto("/tmp/google/protobuf/descriptor.proto");
final FileDescriptorProto optionsFDProto = 
self.loadProto("/tmp/protobuf-options.proto");
final FileDescriptorProto fakeBoxcarFDProto = 
self.loadProto("/tmp/example.proto");

final FileDescriptor fD = FileDescriptor.buildFrom(descriptorFDProto, 
new FileDescriptor[0]);
final FileDescriptor optionsFD = 
FileDescriptor.buildFrom(optionsFDProto, new FileDescriptor[] { fD });
final FileDescriptor fakeBoxcarFD = 
FileDescriptor.buildFrom(fakeBoxcarFDProto, new FileDescriptor[] { optionsFD });

final FieldDescriptor optionsFieldDescriptor = 
optionsFD.findExtensionByName("scrub");
if (optionsFieldDescriptor == null) {
System.out.println("Did not find scrub's FieldDescriptor");
System.exit(1);
}
final FieldDescriptor sFieldDescriptor = 
fakeBoxcarFD.findMessageTypeByName("M").findFieldByName("field2");
System.out.println("unknown option fields 
"+sFieldDescriptor.getOptions().getUnknownFields());
final boolean hasScrubOption = 
sFieldDescriptor.getOptions().hasField(optionsFieldDescriptor);
System.out.println("hasScrubOption: "+hasScrubOption);

}}

When I run LoadFDs, it fails with this exception:

unknown option fields 5: 1

Exception in thread "main" java.lang.IllegalArgumentException: 
FieldDescriptor does not match message type. at 

Re: [protobuf] Re: Protobuf 3.2.0 + Qt 5.8 (Windows)

['Adam Cozzette' via Protocol Buffers]

My first guess would be that you are somehow mixing different protobuf
versions: using generated code from a new version of protoc with a protobuf
runtime library of an older version. Is that true for your Windows setup?

On Fri, Mar 3, 2017 at 3:19 AM, Mastic Cover  wrote:

> EDIT:
>
> Tested this:
>
>
>
> *# Google Protocol Buffers libraryINCLUDEPATH +=
> "C:\\protobuf\\install\\include"LIBS += -L"C:\\protobuf\\install\\lib"
> -llibprotobuf*
>
> And this one:
>
>
>
> *# Google Protocol Buffers libraryINCLUDEPATH +=
> "C:\\protobuf\\install\\include"LIBS += -L"C:\\protobuf\\install\\lib"
> -lprotobuf*
>
>
> Same result over and over again.
>
>
>
>
>
> El viernes, 3 de marzo de 2017, 12:16:14 (UTC+1), Mastic Cover escribió:
>>
>> Hi everyone,
>>
>> I'm trying to build Protobuf with Minwg from MSYS2 as specified in
>> documentation (C++ Installation - Windows). Everything goes perfect and all
>> libraries are created.
>>
>> The problem comes trying to compile and test the "addressbook" sample in
>> Qt/C++. After generating the .pb.cc and .pb.h, I add this to my .pro file
>> inside my Qt project:
>>
>>
>>
>>
>> *# Google Protocol Buffers libraryINCLUDEPATH +=
>> "C:\\protobuf\\install\\include"LIBS += -L"C:\\protobuf\\install\\lib"
>> -llibprotobuf*
>>
>>
>> A lot of "undefined reference" errors (almost 200 errors) are shown and I
>> am not able to make it work:
>>
>>
>>
>>
>>
>>
>>
>> *C:\Qt Developments\MyProject\protoFolder\addressbook.pb.cc:86
>> : error: undefined reference to
>> `google::protobuf::internal::AssignDescriptors(std::string const&,
>> google::protobuf::internal::MigrationSchema const*,
>> google::protobuf::Message const* const*, unsigned int const*,
>> google::protobuf::MessageFactory*, google::protobuf::Metadata*,
>> google::protobuf::EnumDescriptor const**,
>> google::protobuf::ServiceDescriptor const**)'C:\Qt
>> Developments\MyProject\protoFolder\addressbook.pb.cc:97
>> : error: undefined reference to
>> `google::protobuf::internal::RegisterAllTypes(google::protobuf::Metadata
>> const*, int)'C:\Qt Developments\MyProject\protoFolder\addressbook.pb.cc:112
>> : error: undefined reference to
>> `google::protobuf::internal::VerifyVersion(int, int, char const*)'And so
>> on...*
>>
>> Has anyone ever come across this error? Same proccess, same project,
>> tested in a Fedora machine... it works like a charm! But I have to make it
>> work on Windows :(
>>
>> Thanks in advance for your help.
>>
>> Mastic.
>>
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