[Edit: this comment is outdated.] I have a concern about this approach - this will change too much of the generated code and added these ::Google::Protobuf::DescriptorPool.generated_pool.lookup(<class>).msgclass calls to the runtime. I am hoping that we can fix the logic in the RubyTypeOf function to preserve the current generated code.

[Edit: this comment is outdated.] Looks like we should revert part of #23501 - in particular, we do need to pass the package parameter from PrintMethod() to RubyTypeOf. Inside RubyTypeOf, if the passed in object (the descriptor parameter) is in the same package as the package parameter (i.e. the package of the whole file itself), then we should remove the package part from descriptor->full_name() first, before the rest of the consideration with the optional ruby package name stuff.

So effectively, we need to add back these 3 lines https://github.com/grpc/grpc/pull/23501/files#diff-79b87df87999171e709bcdf2ea5a6d82L122-L124, I think.

@HannahShiSFB Thanks for passing all the tests. I think there's one more final step: please run the ./pb/generate_proto_ruby.sh script from the src/ruby directory with your new grpc_ruby_plugin. This should re-generate a few .rb files that's being used by the tests. (My count is 8 more.) Please check those in and then we can re-run these PR one more time.

In order to run generate_proto_ruby.sh, you will first need to run these first:

$ ./tools/bazel build @com_google_protobuf//:protoc
$ ./tools/bazel build src/compiler:grpc_ruby_plugin

Thanks!

@apolcyn Some notes for your review:

• The main fix is to add this "." in front of the fully qualified proto message class name, so that it will be converted into an absolute path starting with :: as the Ruby package name. See this comment and this comment for the rationale for the fix. You may probably want to review the logic of this.

• There are new tests added, and a test updated, in the PR.

• Backport for v1.31.x is in Backport of #23765 to v1.31.x branch #23830. Backport for v1.30.x is in Backport of #23765 to v1.30.x branch #23831.

• We also ran the src/ruby/pb/generate_proto_ruby.sh script to re-generate some generated files that will be updated by this protoc plugin change.

• NOTE that, by running this generate_proto_ruby.sh script, 8 files were being updated in the master branch and the v1.31.x branch, while 6 files were being updated in the v1.30.x branch, likely due to some additional changes to the relevant .proto files after v1.30.

• Updating the generated *_pb.rb files will benefit PHP & Ruby xds interop tests: add support for xds splitting and routing #23763, which is the PR to update the xDS tests according to the latest spec.

All tests passed!