The following changes need to be made to become spec compliant.
Each instance of a method signature annotation is to be treated as a target signature
The fields to include in the signature are to be defined as a comma delimited string
The current implementation incorrectly assumes that there is only ever one target method signature to implement. It also collects all of the signature annotation entries on a method and treats them as the fields to output in the target signature.
The current implementation of support for method signature options is compliant with the specification defined in googleapis/api-common-protos/client.proto#L79
The following changes need to be made to become spec compliant.
The current implementation incorrectly assumes that there is only ever one target method signature to implement. It also collects all of the signature annotation entries on a method and treats them as the fields to output in the target signature.