merging protos with Any fields generates a fictional, invalid proto field

[vchudnov-g]

So far I've only seen this in generated proto messages that have a field of type protobuf.Any. If one merges such a proto file with another one, a new fictional field is created in the message containing the Any. The fictional field is is listed inside the .proto file as null google = XXX, where XXX is a field number. What's even stranger is that this happens even if the "previous" .proto being merged with came from the exact same source as the current proto being generated.

Reproduction steps:

1. Disable the check in copyField() introduced in fix(merge): disable merging proto fields when both old and new versions have type==null #112:

    if (valueType == null && keyType == null) {      
      // return null;    <-- disable this line
   

2. Generate the proto file /tmp/compute.examine.0.proto without merging with any previous proto (no --previous_proto_file_path):

   java -jar target/disco-to-proto3-converter-0.0.1-SNAPSHOT-jar-with-dependencies.jar "--discovery_doc_path=${DIREGAPIC_GOOGLEAPIS}/google/cloud/compute/v1/compute.v1.json" '--service_ignorelist=HttpHealthChecks,HttpsHealthChecks' '--message_ignorelist=HttpHealthCheck,HttpsHealthCheck,HttpHealthCheckList,HttpsHealthCheckList,GetHttpHealthCheckRequest,GetHttpsHealthCheckRequest,PatchHttpHealthCheckRequest,PatchHttpsHealthCheckRequest,UpdateHttpHealthCheckRequest,UpdateHttpsHealthCheckRequest,InsertHttpHealthCheckRequest,InsertHttpsHealthCheckRequest,ListHttpHealthChecksRequest,ListHttpsHealthChecksRequest,DeleteHttpHealthCheckRequest,DeleteHttpsHealthCheckRequest' '--enums_as_strings=True' '--output_file_path=/tmp/compute.examine.0.proto'
   

3. Generate the proto file /tmp/compute.examine.1.proto from the same source, but merging with the previous /tmp/compute.examine.0.proto (with the --previous_proto_file_path):

   java -jar target/disco-to-proto3-converter-0.0.1-SNAPSHOT-jar-with-dependencies.jar "--discovery_doc_path=${DIREGAPIC_GOOGLEAPIS}/google/cloud/compute/v1/compute.v1.json" "--previous_proto_file_path=/tmp/compute.examine.0.proto" '--service_ignorelist=HttpHealthChecks,HttpsHealthChecks' '--message_ignorelist=HttpHealthCheck,HttpsHealthCheck,HttpHealthCheckList,HttpsHealthCheckList,GetHttpHealthCheckRequest,GetHttpsHealthCheckRequest,PatchHttpHealthCheckRequest,PatchHttpsHealthCheckRequest,UpdateHttpHealthCheckRequest,UpdateHttpsHealthCheckRequest,InsertHttpHealthCheckRequest,InsertHttpsHealthCheckRequest,ListHttpHealthChecksRequest,ListHttpsHealthChecksRequest,DeleteHttpHealthCheckRequest,DeleteHttpsHealthCheckRequest' '--enums_as_strings=True' '--output_file_path=/tmp/compute.examine.1.proto'
   

4. Diff /tmp/compute.examine.0.proto and /tmp/compute.examine.0.proto

[vchudnov-g]

This is related, or possibly the same issue, as #114.