Let's assume we have the following structure:
message Alpha {
message Beta {
optional int32 mercury = 1;
optional int32 venus = 2;
}
optional int32 earth = 1;
optional Beta mars = 2;
}
The Java generated code allows to get a sub-builder for "mars" field from a builder for an Alpha message by calling Alpha.newBuilder().getMarsBuilder(). This is nice because I can keep builders for structured messages and update them as needed and build the Alpha message as needed, but still hold on to the big builder which I plan to update further.
But I do not think there is a way to do this in a generic way, using Message.Builder interface. Is there any plan for something like this?