Changes announced April 11, 2023

Syntax Reflection Deprecation

v23 will deprecate the ability to check syntax version using reflection. The deprecation will be included as warnings at build time. The capability will be removed in a future release.

Adding support for ctype=CORD in C++

v23 will add ctype=CORD support for singular bytes fields, including oneof fields, to specify that data should be stored using absl::cord instead of string. Support may be added in future releases for singular string field types and for repeated string and byte fields if there is enough interest from the open source community.

ctype=CORD will have no effect on extensions.

You will be able to add the support using field options:

optional bytes foo = 25 [ctype=CORD];

Option Retention

Options now have a notion of retention, which controls whether an option is retained in the generated code. Options have always had runtime retention by default, meaning that they are retained in the generated code and are thus visible at runtime in the generated descriptor pool. However, you can now set retention = RETENTION_SOURCE to specify that an option (or field within an option) must not be retained at runtime. This is called source retention.

Setting retention looks like this:

extend google.protobuf.FileOptions {
  optional int32 source_retention_option = 1234
      [retention = RETENTION_SOURCE];
}

It can also be set on a plain field, in which case it takes effect only when that field appears inside an option:

message OptionsMessage {
  optional int32 source_retention_field = 1 [retention = RETENTION_SOURCE];
}

For more information, see Option Retention.

Dropping Support for Bazel <5.3

v23 will drop support for Bazel 4. Protobuf will continue to support the Bazel 5 LTS with Bazel 5.3 as the minimum required version. This is per the build support policy described in Foundational C++ Support Policy and as reflected in the versions in Foundational C++ Support.