Add the Rust codegen to protoc

After this change, the Rust codegen can be enabled via the protoc flag '--rust_out'. Due to its experimental nature we require a magic value to be provided '--rust_out=experimental-codegen=enabled:<out>'.

Make the 'RustGenerator' create an empty *.pb.rs file.

PiperOrigin-RevId: 512644570

pkg/BUILD.bazel

@@ -386,6 +386,7 @@ cc_dist_library(
         "//src/google/protobuf/compiler/php",
         "//src/google/protobuf/compiler/python",
         "//src/google/protobuf/compiler/ruby",
+        "//src/google/protobuf/compiler/rust",
     ],
     dist_deps = [
         ":protobuf",

src/google/protobuf/compiler/BUILD.bazel

@@ -115,6 +115,7 @@ cc_library(
         "//src/google/protobuf/compiler/php",
         "//src/google/protobuf/compiler/python",
         "//src/google/protobuf/compiler/ruby",
+        "//src/google/protobuf/compiler/rust",
         "@com_google_absl//absl/log:initialize",
     ],
 )

src/google/protobuf/compiler/main.cc

@@ -39,6 +39,7 @@
 #include "google/protobuf/compiler/python/generator.h"
 #include "google/protobuf/compiler/python/pyi_generator.h"
 #include "google/protobuf/compiler/ruby/ruby_generator.h"
+#include "google/protobuf/compiler/rust/generator.h"
 
 // Must be included last.
 #include "google/protobuf/port_def.inc"
@@ -112,6 +113,10 @@ int ProtobufMain(int argc, char* argv[]) {
   cli.RegisterGenerator("--objc_out", "--objc_opt", &objc_generator,
                         "Generate Objective-C header and source.");
 
+  // Rust
+  rust::RustGenerator rust_generator;
+  cli.RegisterGenerator("--rust_out", &rust_generator,
+                        "Generate Rust sources.");
   return cli.Run(argc, argv);
 }
 

src/google/protobuf/compiler/rust/BUILD.bazel

@@ -7,6 +7,7 @@ load("//build_defs:cpp_opts.bzl", "COPTS")
 
 cc_library(
     name = "rust",
+    srcs = ["generator.cc"],
     hdrs = ["generator.h"],
     copts = COPTS,
     include_prefix = "google/protobuf/compiler/rust",

src/google/protobuf/compiler/rust/generator.cc

@@ -0,0 +1,87 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include "google/protobuf/compiler/rust/generator.h"
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "absl/algorithm/container.h"
+#include "absl/strings/str_cat.h"
+#include "absl/strings/string_view.h"
+#include "google/protobuf/descriptor.h"
+#include "google/protobuf/io/printer.h"
+
+namespace google {
+namespace protobuf {
+namespace compiler {
+namespace rust {
+
+bool ExperimentalRustGeneratorEnabled(
+    const std::vector<std::pair<std::string, std::string>>& options) {
+  static constexpr std::pair<absl::string_view, absl::string_view> kMagicValue =
+      {"experimental-codegen", "enabled"};
+
+  return absl::c_any_of(
+      options, [](std::pair<absl::string_view, absl::string_view> pair) {
+        return pair == kMagicValue;
+      });
+}
+
+bool RustGenerator::Generate(const FileDescriptor* file,
+                             const std::string& parameter,
+                             GeneratorContext* generator_context,
+                             std::string* error) const {
+  std::vector<std::pair<std::string, std::string>> options;
+  ParseGeneratorParameter(parameter, &options);
+
+  if (!ExperimentalRustGeneratorEnabled(options)) {
+    *error =
+        "The Rust codegen is highly experimental. Future versions will break "
+        "existing code. Use at your own risk. You can opt-in by passing "
+        "'experimental-codegen=enabled' to '--rust_out'.";
+    return false;
+  }
+
+  auto basename = StripProto(file->name());
+  auto outfile = absl::WrapUnique(
+      generator_context->Open(absl::StrCat(basename, ".pb.rs")));
+
+  google::protobuf::io::Printer(outfile.get()).Emit(R"cc(
+    // TODO: Generate Bindings
+  )cc");
+  return true;
+}
+
+}  // namespace rust
+}  // namespace compiler
+}  // namespace protobuf
+}  // namespace google

src/google/protobuf/compiler/rust/generator.h

@@ -33,7 +33,6 @@
 
 #include <string>
 
-#include "absl/log/absl_check.h"
 #include "google/protobuf/compiler/code_generator.h"
 
 // Must be included last.
@@ -53,10 +52,7 @@ class RustGenerator final : public google::protobuf::compiler::CodeGenerator {
 
   bool Generate(const FileDescriptor* file, const std::string& parameter,
                 GeneratorContext* generator_context,
-                std::string* error) const override {
-    ABSL_CHECK(false) << "not yet implemented";
-    return false;
-  }
+                std::string* error) const override;
 
   uint64_t GetSupportedFeatures() const override {
     return FEATURE_PROTO3_OPTIONAL;