proto: distinguish between invalid and empty messages in Equal

The v1 proto.Equal function treats (*Message)(nil) and new(Message)
as being different, while v2 proto.Equal treated them as equal since
a typed nil pointer is functionally an empty message since the
protobuf data model has no concept of presence as a first-class
property of messages.

Unfortunately, a significant amount of code depends on this distinction
that it would be difficult to migrate users from v1 to v2 unless we
preserved similar semantics in the v2 proto.Equal.

Also, double down on these semantics for protocmp.Transform.

Fixes #965

Change-Id: I21e78ba6251401a0ac0ccf495188093973cd7f3f
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/213238
Reviewed-by: Damien Neil <dneil@google.com>
6 files changed
tree: 662eb878aee5eddc4f0ef2dfc1aea7cca432abf4
  1. benchmarks/
  2. cmd/
  3. compiler/
  4. encoding/
  5. internal/
  6. proto/
  7. reflect/
  8. runtime/
  9. testing/
  10. types/
  11. .gitignore
  12. .travis.yml
  13. AUTHORS
  14. CONTRIBUTING.md
  15. CONTRIBUTORS
  16. go.mod
  17. go.sum
  18. integration_test.go
  19. LICENSE
  20. PATENTS
  21. README.md
  22. regenerate.bash
  23. release.bash
  24. test.bash
README.md

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:

Contributing

We appreciate community contributions. See CONTRIBUTING.md.

Reporting Issues

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