[protobuf-go] How to access field extensions.

[marwan-at-work]

Hi there, I have the following protobuf file:

syntax = "proto3";
package example;
option go_package = "...";
import "options.proto";

message MyMessage {
  string ID = 1 [(optionspkg.name) = "id"];
}

And I am writing a plugin in protobuf-go using protogen.

My question is: how can I access options.pkg.name and its value "id" from *protogen.Field?

It seems that I can call field.Desc.Options() which does return *descriptorpb.FieldOptions which has the options in an unexported field : extensionFields protoimpl.ExtensionFields so I'm unable to access it.

Thanks!

[marwan-at-work]

Ah, it looks like I can use this function: https://pkg.go.dev/google.golang.org/protobuf/proto#GetExtension

It might be worth documenting it here?: https://github.com/protocolbuffers/protobuf-go/blob/eba8b0975f4efc219baabc1e0e13df28a6e1ad28/reflect/protoreflect/type.go#L109

[emicklei]

One hint that could have helped me is that the protoreflect.ExtensionType argument instance can be found in the generated proto definition of your extension.

For example in my protocheck package, I have this code line:

ext, ok := proto.GetExtension(fops, protocheck.E_Field).(*protocheck.Check)