Specifying // +protobuf.nullable=true on a Go type that is an alias of a
map or slice will generate a synthetic protobuf message with the type
name that will serialize to the wire in a way that allows the difference
between empty and nil to be recorded.
For instance:
// +protobuf.nullable=true
types OptionalMap map[string]string
will create the following message:
message OptionalMap {
map<string, string> Items = 1
}
and generate marshallers that use the presence of OptionalMap to
determine whether the map is nil (rather than Items, which protobuf
provides no way to delineate between empty and nil).
The protobuf tags contain the assigned tag id, which then ensures
subsequent generation is consistently tagging (tags don't change across
generations unless someone deletes the protobuf tag).
In addition, generate final proto IDL that is free of gogoproto
extensions for ease of generation into other languages.
Add a flag --keep-gogoproto which preserves the gogoproto extensions in
the final IDL.
