Would it be worth mentioning on the Google documentation pages that Self-Describing messages are not supported in Proto3?
https://developers.google.com/protocol-buffers/docs/techniques jh On Thursday, December 3, 2015 at 4:46:29 AM UTC-8, Jon Skeet wrote: > > I agree it's a limitation - but it just comes naturally with the territory > of only supporting proto3. > > Now there's nothing to say that we'll *never* support proto2 - but the > extra complexity of supporting extensions and different models of field > presence would have significantly delayed the whole effort. (It would also > have made the code base harder to maintain - I'm much happier with the new > code base than the old proto2-only one...) > > Jon > > On Wednesday, 2 December 2015 16:56:12 UTC, James Hugard wrote: >> >> Hi Jon: >> >> Pity that there will be no official support. That means I shall be >> unable to have fully self-describing messages. Further, I believe that >> will also preclude writing proto compiler plugins in C# (F#, VB, etc.). >> >> As an interim solution (or a permanent one?), I have hand-edited >> Descriptor.proto to remove everything incompatible with proto3, compiled it >> with proto3 syntax, thus generating C# code. The main issue is support for >> extension ranges - without those, it is impossible to declare custom >> options (which we also use). Therefore, I simply compiled all other proto >> files using the original (proto2) descriptor.proto file then hand edited >> the generated code to reference >> Google.ProtocolBuffers.DescriptorProtos.FileDescriptorProto. >> >> Less than ideal, and certainly not acceptable for production use. >> >> I'm eyeing the Froto <https://github.com/ctaggart/froto> project as a >> possible long-term solution, but with a need to support many languages >> that's also less than ideal and would take .NET out of the primary >> ecosystem. >> >> Thanks for the reply! >> >> jh >> >> >> On Wednesday, December 2, 2015 at 6:46:52 AM UTC-8, Jon Skeet wrote: >>> >>> On Wednesday, 2 December 2015 04:45:30 UTC, James Hugard wrote: >>>> >>>> Trying to use a FileDescriptorSet in my own proto3 message definition >>>> with C# 3.0.0-alpha4 generated code, but running into compilation issues. >>>> >>>> The code generates just fine using protoc.exe, but the generated code >>>> won't compile due to a missing reference to "global >>>> ::Google.Protobuf.FileDescriptorSet". >>>> >>>> Attempting to generate code from the protobuf definition fails, because >>>> the Descriptor.proto file uses proto2 syntax and hence is not supported by >>>> the C# code generator. >>>> >>>> A C# object for FileDescriptorSet does not appear to be in >>>> Google.Protobuf assembly. Nor could I figure out how to modify the >>>> generated code to compile properly. Attempting to manually edit the >>>> generated code to use >>>> >>>> Google.Protobuf.Collections.RepeatedField< >>>> Google.Protobuf.Reflection.FileDescriptor > failed with a "no >>>> conversion to IMessage<>", or something similar. >>>> >>>> >>>> Please, what is the right way to use a FileDescriptorSet in my own >>>> proto? >>>> >>> >>> I'm afraid you can't. We generate the code for descriptor.proto so that >>> we can use it within the protobuf runtime, but it's all internal - we don't >>> have any codegen to support proto2 semantics, and we've carefully looked at >>> what we need from descriptor.proto to check that it's okay with what we >>> need to use it for internally, but that's all. It would be a bad idea to >>> expose it separately. >>> >>> If we ever retroactively fit proto2 support, that would be fine, of >>> course - but until then, I'm afraid there's no way of doing this. You could >>> create your own proto3 copy of descriptor.proto, taking only the bits you >>> care about, and if you're very careful you *may* then be able to >>> interoperate with code that actually expects a FileDescriptorSet... but you >>> would definitely need to be careful. >>> >>> Jon >>> >>> >> -- You received this message because you are subscribed to the Google Groups "Protocol Buffers" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/protobuf. For more options, visit https://groups.google.com/d/optout.
