Inverse of ToDescriptorProto?

[Bob Glickstein]

In Go, using google.golang.org/prot...@v1.25.0, I can turn a proto.Message m into a serialized description of its type like this:

ref := m.ProtoReflect()
desc := ref.Descriptor()
descProto := protodesc.ToDescriptorProto(desc)
proto.Marshal(descProto)

I would like to take a serialized type t like this and turn it back into a (blank) proto.Message of the appropriate type. (Error checks etc. omitted for clarity.)

var descProto descriptorpb.DescriptorProto
err := proto.Unmarshal(t, &descProto)
desc := ThisOperationDoesNotExist(&descProto) // The problem.
m := dynamicpb.NewMessage(desc)

I've been able to make ThisOperationDoesNotExist work by faking up a FileDescriptorSet, like this:

descProtos := []*descriptorpb.DescriptorProto{&descProto}
name := "x"
fdProtos := []*descriptorpb.FileDescriptorProto{{Name: &name, MessageType: descProtos}}
fdSet := &descriptorpb.FileDescriptorSet{File: fdProtos}
f, err := protodesc.NewFiles(fdSet)
&descriptorpb.FileDescriptorSet{File: []*descriptorpb.FileDescriptorProto{{Name: &name, MessageType: []*descriptorpb.DescriptorProto{&dp}}}})

var desc protoreflect.MessageDescriptor
f.RangeFiles(func(fileDesc protoreflect.FileDescriptor) bool {
  msgDescs := fileDesc.Messages()
  desc = msgDescs.Get(0)
})

but that's pretty ugly, and probably brittle. Is there another way? And if there isn't, can one be added?

Thanks,

- Bob

[Bob Glickstein]

On Wed, Jul 8, 2020 at 9:37 AM Bob Glickstein <bob.gli...@gmail.com> wrote:

I've been able to make ThisOperationDoesNotExist work by faking up a FileDescriptorSet, like this:

Copy-paste error in my original message, sorry. It should be:

 

descProtos := []*descriptorpb.DescriptorProto{&descProto}
name := "x"
fdProtos := []*descriptorpb.FileDescriptorProto{{Name: &name, MessageType: descProtos}}
fdSet := &descriptorpb.FileDescriptorSet{File: fdProtos}
f, err := protodesc.NewFiles(fdSet)

var desc protoreflect.MessageDescriptor
f.RangeFiles(func(fileDesc protoreflect.FileDescriptor) bool {
  msgDescs := fileDesc.Messages()
  desc = msgDescs.Get(0)
})

Cheers,

- Bob