[CodeGen][CPP] Added support for service "deprecated" option (#38493)

In proto we can add deprecated option in service definition
example:
```
service Greeter {
   option deprecated = true;
```
This PR help in translating this to marking generated service class as deprecated (which enables warning while using)

`class [[deprecated]] Greeter final {`

Sample warning

```
/usr/local/google/home/bpawan/workspace/code/grpc/examples/cpp/helloworld/greeter_async_client.cc:104:28: warning: 'Greeter' is deprecated [-Wdeprecated-declarations]
  104 |   std::unique_ptr<Greeter::Stub> stub_;
```

Encapsulated support with compiler flag "allow_deprecated" which will be by default false . Hence will not be impacted existing users

Closes #38493

COPYBARA_INTEGRATE_REVIEW=https://github.com/grpc/grpc/pull/38493 from pawbhard:deprecated-support bd143e37ac
PiperOrigin-RevId: 723134226

bazel/cc_grpc_library.bzl

@@ -25,6 +25,7 @@ def cc_grpc_library(
         proto_only = False,
         well_known_protos = False,
         generate_mocks = False,
+        allow_deprecated = False,
         use_external = False,  # @unused
         grpc_only = False,
         **kwargs):
@@ -56,6 +57,8 @@ def cc_grpc_library(
           (passed in srcs parameter) instead. False by default.
         generate_mocks (bool): when True, Google Mock code for client stub is
           generated. False by default.
+        allow_deprecated (bool): when True, Generated class will marked
+          deprecated if deprecated option is set in proto.
         use_external (bool): Not used.
         grpc_only (bool): if True, generate only grpc library, expecting
           protobuf messages library (cc_proto_library target) to be passed as
@@ -105,6 +108,7 @@ def cc_grpc_library(
             plugin = Label("//src/compiler:grpc_cpp_plugin"),
             well_known_protos = well_known_protos,
             generate_mocks = generate_mocks,
+            allow_deprecated = allow_deprecated,
             **kwargs
         )
 

bazel/generate_cc.bzl

@@ -121,6 +121,7 @@ def generate_cc_impl(ctx):
             ctx.attr.flags,
             dir_out,
             ctx.attr.generate_mocks,
+            ctx.attr.allow_deprecated,
         )
         tools = [ctx.executable.plugin]
     else:
@@ -186,6 +187,10 @@ _generate_cc = rule(
             default = False,
             mandatory = False,
         ),
+        "allow_deprecated": attr.bool(
+            default = False,
+            mandatory = False,
+        ),
         "_protoc": attr.label(
             default = Label("@com_google_protobuf//:protoc"),
             executable = True,

bazel/grpc_build_system.bzl

@@ -302,7 +302,8 @@ def grpc_cc_grpc_library(
         srcs = [],
         deps = [],
         visibility = None,
-        generate_mocks = False):
+        generate_mocks = False,
+        allow_deprecated = False):
     """A wrapper around cc_grpc_library that forces grpc_only=True.
 
     Callers are expected to have their own proto_library() and
@@ -315,6 +316,7 @@ def grpc_cc_grpc_library(
         deps = deps,
         visibility = visibility,
         generate_mocks = generate_mocks,
+        allow_deprecated = allow_deprecated,
         grpc_only = True,
     )
 

bazel/protobuf.bzl

@@ -125,6 +125,7 @@ def get_plugin_args(
         flags,
         dir_out,
         generate_mocks,
+        allow_deprecated = False,
         plugin_name = "PLUGIN"):
     """Returns arguments configuring protoc to use a plugin for a language.
 
@@ -133,6 +134,8 @@ def get_plugin_args(
       flags: The plugin flags to be passed to protoc.
       dir_out: The output directory for the plugin.
       generate_mocks: A bool indicating whether to generate mocks.
+      allow_deprecated: A bool indicating whether to mark generated class deprecated
+      based on deprecated proto option in service file.
       plugin_name: A name of the plugin, it is required to be unique when there
       are more than one plugin used in a single protoc command.
     Returns:
@@ -141,6 +144,8 @@ def get_plugin_args(
     augmented_flags = list(flags)
     if generate_mocks:
         augmented_flags.append("generate_mock_code=true")
+    if allow_deprecated:
+        augmented_flags.append("allow_deprecated=true")
 
     augmented_dir_out = dir_out
     if augmented_flags:

src/compiler/cpp_generator.cc

@@ -1404,9 +1404,15 @@ void PrintHeaderService(grpc_generator::Printer* printer,
   (*vars)["Service"] = service->name();
 
   printer->Print(service->GetLeadingComments("//").c_str());
-  printer->Print(*vars,
-                 "class $Service$ final {\n"
-                 " public:\n");
+  if (params.allow_deprecated && service->is_deprecated()) {
+    printer->Print(*vars,
+                   "class [[deprecated]] $Service$ final {\n"
+                   " public:\n");
+  } else {
+    printer->Print(*vars,
+                   "class $Service$ final {\n"
+                   " public:\n");
+  }
   printer->Indent();
 
   // Service metadata

src/compiler/cpp_generator.h

@@ -68,6 +68,8 @@ struct Parameters {
   bool allow_sync_server_api;
   // Whether to generate completion queue API.
   bool allow_cq_api;
+  // whether to add deprecated warning for services
+  bool allow_deprecated;
 };
 
 // Return the prologue of the generated header file.

src/compiler/cpp_plugin.h

@@ -67,6 +67,7 @@ class CppGrpcGenerator : public grpc::protobuf::compiler::CodeGenerator {
     generator_parameters.include_import_headers = false;
     generator_parameters.allow_sync_server_api = true;
     generator_parameters.allow_cq_api = true;
+    generator_parameters.allow_deprecated = false;
 
     ProtoBufFile pbfile(file);
 
@@ -129,6 +130,15 @@ class CppGrpcGenerator : public grpc::protobuf::compiler::CodeGenerator {
             *error = std::string("Invalid parameter: ") + *parameter_string;
             return false;
           }
+        } else if (param[0] == "allow_deprecated") {
+          if (param[1] == "true") {
+            generator_parameters.allow_deprecated = true;
+          } else if (param[1] == "false") {
+            generator_parameters.allow_deprecated = false;
+          } else {
+            *error = std::string("Invalid parameter: ") + *parameter_string;
+            return false;
+          }
         } else {
           *error = std::string("Unknown parameter: ") + *parameter_string;
           return false;

src/compiler/protobuf_plugin.h

@@ -108,6 +108,7 @@ class ProtoBufService : public grpc_generator::Service {
       : service_(service) {}
 
   std::string name() const { return std::string(service_->name()); }
+  bool is_deprecated() const { return service_->options().deprecated(); }
 
   int method_count() const { return service_->method_count(); }
   std::unique_ptr<const grpc_generator::Method> method(int i) const {

src/compiler/schema_interface.h

@@ -81,6 +81,7 @@ struct Service : public CommentHolder {
   virtual ~Service() {}
 
   virtual std::string name() const = 0;
+  virtual bool is_deprecated() const = 0;
 
   virtual int method_count() const = 0;
   virtual std::unique_ptr<const Method> method(int i) const = 0;

src/proto/grpc/testing/BUILD

@@ -52,6 +52,7 @@ grpc_cc_proto_library(
 grpc_cc_grpc_library(
     name = "compiler_test_cc_grpc",
     srcs = ["compiler_test_proto"],
+    allow_deprecated = True,
     generate_mocks = True,
     deps = ["compiler_test_cc_proto"],
 )

src/proto/grpc/testing/compiler_test.proto

@@ -64,6 +64,8 @@ service ServiceA {
 service ServiceB {
   // ServiceB trailing comment 1
 
+  option deprecated = true;
+
   // MethodB1 leading comment 1
   rpc MethodB1(Request) returns (Response);
   // MethodB1 trailing comment 1

test/cpp/codegen/compiler_test_golden

@@ -712,7 +712,7 @@ class ServiceA final {
 };
 
 // ServiceB leading comment 1
-class ServiceB final {
+class [[deprecated]] ServiceB final {
  public:
   static constexpr char const* service_full_name() {
     return "grpc.testing.ServiceB";