Added support for Protobuf Extensions in Rust This CL introduces support for [Protobuf Extensions](https://engdoc.corp.google.com/eng/doc/devguide/proto/programming-guides/proto2.html#extensions) to the Rust Protobuf library, a key feature for full Proto2 API parity. Key changes include: 1. **Code Generation:** * Added `compiler/rust/extension.cc` and `extension.h` to handle the generation of Rust code for extension definitions. * Updated `generator.cc` and `message.cc` to invoke extension generation for both top-level and nested extensions. * Generates `ExtensionId` constants for each extension. 2. **Runtime API (`rust/extension.rs`):** * Introduced the generic `ExtensionId<Extendee, T>` type to identify and type-check extensions. * Defined traits for extension operations: `ExtHas`, `ExtGet`, `ExtSet`, `ExtClear`, and `ExtGetMut`. * Implemented methods on `ExtensionId` that dispatch to the trait implementations provided by the active kernel. 3. **Kernel Implementations:** * **C++ Kernel (`rust/cpp_kernel/extension.rs`):** Implemented extension traits by calling into new C++ FFI functions (defined in `rust/cpp_kernel/extension.cc`) that interact with the C++ `ExtensionSet`. * **UPB Kernel (`rust/upb_kernel/extension.rs`):** Implemented extension traits using UPB's MiniTable-based extension API. Extension MiniTables are registered at static initialization time using the `linkme` crate. 4. **Build System:** * Updated `protobuf/rust/BUILD` and `protobuf/compiler/rust/BUILD` to include new files. * Added a dependency on `//third_party/rust/linkme/v0_3` for the UPB kernel's extension registration. 5. **Testing:** * Added `test/extensions.proto` and `test/extensions_separate_file.proto` to define various extension types. * Added `test/shared/extensions_test.rs` with comprehensive tests covering presence, getters, setters, defaults, nested extensions, submessage extensions, repeated extensions, serialization, and `MergeFrom`. This change enables Rust users to define and interact with Protobuf extensions in a type-safe manner, compatible with both the C++ and UPB runtimes. PiperOrigin-RevId: 803898684
Copyright 2008 Google LLC
Protocol Buffers (a.k.a., protobuf) are Google's language-neutral, platform-neutral, extensible mechanism for serializing structured data. You can learn more about it in protobuf's documentation.
This README file contains protobuf installation instructions. To install protobuf, you need to install the protocol compiler (used to compile .proto files) and the protobuf runtime for your chosen programming language.
Most users will find working from supported releases to be the easiest path.
If you choose to work from the head revision of the main branch your build will occasionally be broken by source-incompatible changes and insufficiently-tested (and therefore broken) behavior.
If you are using C++ or otherwise need to build protobuf from source as a part of your project, you should pin to a release commit on a release branch.
This is because even release branches can experience some instability in between release commits.
Protobuf supports Bzlmod with Bazel 8 +. Users should specify a dependency on protobuf in their MODULE.bazel file as follows.
bazel_dep(name = "protobuf", version = <VERSION>)
Users can optionally override the repo name, such as for compatibility with WORKSPACE.
bazel_dep(name = "protobuf", version = <VERSION>, repo_name = "com_google_protobuf")
Users can also add the following to their legacy WORKSPACE file.
Note that with the release of 30.x there are a few more load statements to properly set up rules_java and rules_python.
http_archive(
name = "com_google_protobuf",
strip_prefix = "protobuf-VERSION",
sha256 = ...,
url = ...,
)
load("@com_google_protobuf//:protobuf_deps.bzl", "protobuf_deps")
protobuf_deps()
load("@rules_java//java:rules_java_deps.bzl", "rules_java_dependencies")
rules_java_dependencies()
load("@rules_java//java:repositories.bzl", "rules_java_toolchains")
rules_java_toolchains()
load("@rules_python//python:repositories.bzl", "py_repositories")
py_repositories()
The protobuf compiler is written in C++. If you are using C++, please follow the C++ Installation Instructions to install protoc along with the C++ runtime.
For non-C++ users, the simplest way to install the protocol compiler is to download a pre-built binary from our GitHub release page.
In the downloads section of each release, you can find pre-built binaries in zip packages: protoc-$VERSION-$PLATFORM.zip. It contains the protoc binary as well as a set of standard .proto files distributed along with protobuf.
If you are looking for an old version that is not available in the release page, check out the Maven repository.
These pre-built binaries are only provided for released versions. If you want to use the github main version at HEAD, or you need to modify protobuf code, or you are using C++, it's recommended to build your own protoc binary from source.
If you would like to build protoc binary from source, see the C++ Installation Instructions.
Protobuf supports several different programming languages. For each programming language, you can find instructions in the corresponding source directory about how to install protobuf runtime for that specific language:
| Language | Source |
|---|---|
| C++ (include C++ runtime and protoc) | src |
| Java | java |
| Python | python |
| Objective-C | objectivec |
| C# | csharp |
| Ruby | ruby |
| Go | protocolbuffers/protobuf-go |
| PHP | php |
| Dart | dart-lang/protobuf |
| JavaScript | protocolbuffers/protobuf-javascript |
The best way to learn how to use protobuf is to follow the tutorials in our developer guide.
If you want to learn from code examples, take a look at the examples in the examples directory.
The complete documentation is available at the Protocol Buffers doc site.
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