compiler/protogen: deprecate certain ways to derive Go package information

There are currently at least 5 ways to derive Go package information:
* From the 'M' command-line flag.
* From the 'import_path' command-line flag.
* From the 'go_package' proto file option.
* From the proto package name in proto source file.
* From the path of the proto source file.
Technically, there are more than 5 ways since information can be derived
from a convoluted combination of all the methods.

We should move towards a sensible and consistent world where each
Go package information for each proto source file is:
* only derived from the command-line OR
* only derived from the proto source file itself.
It should never be derived from a mixture of methods.

In the future, all .proto source files will be required to have a
"go_package" option specified, unless the "M" command-line argument is
specified. If the "M" flag is given it takes precedence over 'go_package'.

This CL prints warnings if the user is generating proto files without
a "M" flag or "go_package" option specified. It suggests to the user
a "go_package" option that preserves the current semantics.

Change-Id: I5cf8d40a245146bb145b3b610d42f1bcd140b449
Reviewed-by: Damien Neil <>
1 file changed
tree: 31ab9518538c4c8aff66fe4dcf493cb6a9db4bae
  1. .gitignore
  2. .travis.yml
  9. benchmarks/
  10. cmd/
  11. compiler/
  12. encoding/
  13. go.mod
  14. go.sum
  15. integration_test.go
  16. internal/
  17. proto/
  18. reflect/
  19. regenerate.bash
  20. release.bash
  21. runtime/
  22. test.bash
  23. testing/
  24. 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.