protogen: fix oneof name mangling regression

The generator currently uses an unintuitive and stateful algorithm
for name generation where it "fixes" name conflicts by appending "_"
to the end of the new name.

PR#657 refactored the generator code and noticed that the above
algorithm was not properly taking into account that a Get method is
generated for parent oneofs, fixing it in the same PR. While this is
more correct, this breaks users (see #780) since it means that the
generation of names can change.

This PR changes the name mangling logic to be as it was previously.
This does mean that some new proto files may be unbuildable,
but that is arguably better than breaking existing proto files

Change-Id: I2e354f4bb5d9c2b562fa2faa9149e949e2d86a0f
Reviewed-by: Damien Neil <>
3 files changed
tree: 7e75b6d7ea7fc1477dcc27ccc3c3c6e472b754d4
  1. .gitignore
  2. .travis.yml
  9. cmd/
  10. encoding/
  11. go.mod
  12. go.sum
  13. internal/
  14. proto/
  15. protogen/
  16. reflect/
  17. regenerate.bash
  18. runtime/
  19. test.bash
  20. types/

Next Generation Go Protocol Buffers

WARNING: This repository is in active development. There are no guarantees about API stability. Breaking changes will occur until a stable release is made and announced.

This repository is for the development of the next major Go implementation of protocol buffers. This library makes breaking API changes relative to the existing Go protobuf library. Of particular note, this API aims to make protobuf reflection a first-class feature of the API and implements the protobuf ecosystem in terms of reflection.

Design Documents

List of relevant design documents:


We appreciate community contributions. See

Reporting Issues

Issues regarding the new API can be filed at Please use a APIv2: prefix in the title to make it clear that the issue is regarding the new API work.