[Ruby] Provide Ruby wrapper classes for ServiceDescriptor and MethodDescriptor #14891
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anandolee
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I think this makes sense to do. We would welcome a contribution. An easy start would be:
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I'm unassigning myself as I have no immediate plans to work on this, but we would welcome a contribution. |
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I had a need for this (for generating RPC stubs from the proto descriptors, without having to write a protoc plugin), so I implemented I think what you had in mind in #15817 |
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This PR implements lookup of service descriptor and method descriptor objects in Ruby as described in issue #14891. It contains three implementations - one for the CRuby extension API, one for JRuby, and one for FFI. With this patch, * `DescriptorPool#lookup('fully.qualified.service.name')` works and returns a `Google::Protobuf::ServiceDescriptor` object * You can call `#options` on that to get the service options * You can call `#methods` on that to get the services' methods as `Google::Protobuf::MethodDescriptor` objects, * You can call `MethodDescriptor#options` to get method options * You can also get the streaming flags & input/output types of the method with `#input_type`, `#output_type`, `#client_streaming`, and `#server_streaming`. In order to make the FFI implementation work, I had to mark some more methods in the UPB header as exported - I guess that's something which will have to be done on the UPB side, like this protocolbuffers/upb@01fed1c CC @dazuma & @haberman from the original issue, and @JasonLunn (since you work on protobuf it seems - small world!) I apologies for the large volume of copy-pasta'd code from the existing descriptor class implementations into the new ones - I felt this was probably better than designing new abstractions to reduce it off the bat though; this feels like it "fits in" with the existing implementation. Closes #15817 COPYBARA_INTEGRATE_REVIEW=#15817 from KJTsanaktsidis:ktsanaktsidis/add_service_method_descriptors 54d7218 PiperOrigin-RevId: 618221016
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What language does this apply to?
Ruby
Describe the problem you are trying to solve.
The Ruby runtime library provides several Ruby classes
Google::Protobuf::Descriptor,Google::Protobuf::FileDescriptor, etc. that wrap the underlying descriptor objects, along withGoogle::Protobuf::DescriptorPoolthat wraps the defpool and provides a way to look up needed descriptors. These objects are sometimes critical for understanding protobuf descriptors, especially when implementing protoc plugins.However, two objects have no corresponding Ruby class: the service and method descriptors. Hence, it is not possible to access service descriptor information from Ruby.
For example, this makes it extremely difficult to get option extensions for services and methods, as the computation of that information happens on the descriptors. This makes it difficult to write client library generators in Ruby. #1198 was recently closed as complete to address this, but it covered only the descriptor types already existing; there is still no way to get custom option info for services and methods.
Describe the solution you'd like
We propose creating the classes
Google::Protobuf::ServiceDescriptorandGoogle::Protobuf::MethodDescriptor, implemented similarly to the existing descriptor wrapper classes (i.e. a C implementation inruby/ext/google/protobuf_c/defs.[ch], FFI implementations inruby/lib/google/protobuf/ffi/, and JRuby implementations insrc/main/java/com/google/protobuf/jruby/.) Appropriate accessor methods on those classes would need to be determined and designed.Describe alternatives you've considered
We currently do not seem to have a good alternative for getting runtime descriptor information in Ruby. I currently maintain a client library generator, and we had to resort to directly decoding the encoded form of
ServiceOptionsandMethodOptionsdata, and hard-coding field numbers, in order to get the information we need.Additional context
Other languages do seem to have these classes. Example from Python
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