gRPC callbackService support added (#8666)

* grpc callbackService support added

Signed-off-by: shankeleven <shashanksati11@gmail.com>

* tests: regenerate C++ gRPC golden with --grpc-callback-api (CallbackService & async_ reactor APIs); update formatting and method placement

---------

Signed-off-by: shankeleven <shashanksati11@gmail.com>
Co-authored-by: Wouter van Oortmerssen <aardappel@gmail.com>

grpc/tests/BUILD

@@ -17,3 +17,27 @@ cc_test(
         "@com_github_grpc_grpc//:grpc++",
     ],
 )
+
+cc_test(
+    name = "grpc_callback_compile_test",
+    srcs = ["grpctest_callback_compile.cpp"],
+    copts = ["-Itests"],
+    linkstatic = 1,
+    deps = [
+        "//tests:monster_test_cc_fbs",
+        "//tests:monster_test_grpc",
+        "@com_github_grpc_grpc//:grpc++",
+    ],
+)
+
+cc_test(
+    name = "grpc_callback_client_compile_test",
+    srcs = ["grpctest_callback_client_compile.cpp"],
+    copts = ["-Itests"],
+    linkstatic = 1,
+    deps = [
+        "//tests:monster_test_cc_fbs",
+        "//tests:monster_test_grpc",
+        "@com_github_grpc_grpc//:grpc++",
+    ],
+)

grpc/tests/grpctest_callback_client_compile.cpp

@@ -0,0 +1,61 @@
+// Verifies that the generated gRPC callback client stub methods are present.
+// This is a compile-time only test: it never performs an actual RPC.
+// It supplements grpctest_callback_compile.cpp (server side) by checking
+// client-side async_ / reactor entry points.
+
+#include <type_traits>
+
+#include "monster_test.grpc.fb.h"
+
+#if defined(FLATBUFFERS_GENERATED_GRPC_CALLBACK_API) && \
+    defined(GRPC_CALLBACK_API_NONEXPERIMENTAL)
+using Stub = MyGame::Example::MonsterStorage::Stub;
+using namespace MyGame::Example;  // NOLINT
+
+// Unary async overloads
+static_assert(std::is_member_function_pointer<
+                  decltype(static_cast<void (Stub::*)(
+                               ::grpc::ClientContext *,
+                               const flatbuffers::grpc::Message<Monster> &,
+                               flatbuffers::grpc::Message<Stat> *,
+                               std::function<void(::grpc::Status)>)>(
+                      &Stub::async_Store))>::value,
+              "Function-form unary async_Store missing");
+static_assert(std::is_member_function_pointer<
+                  decltype(static_cast<void (Stub::*)(
+                               ::grpc::ClientContext *,
+                               const flatbuffers::grpc::Message<Monster> &,
+                               flatbuffers::grpc::Message<Stat> *,
+                               ::grpc::ClientUnaryReactor *)>(
+                      &Stub::async_Store))>::value,
+              "Reactor-form unary async_Store missing");
+
+// Streaming reactor entry points
+static_assert(
+    std::is_member_function_pointer<
+        decltype(static_cast<void (Stub::*)(
+                     ::grpc::ClientContext *,
+                     const flatbuffers::grpc::Message<Stat> &,
+                     ::grpc::ClientReadReactor<flatbuffers::grpc::Message<
+                         Monster> > *)>(&Stub::async_Retrieve))>::value,
+    "Server streaming reactor async_Retrieve missing");
+static_assert(
+    std::is_member_function_pointer<
+        decltype(static_cast<void (Stub::*)(
+                     ::grpc::ClientContext *,
+                     flatbuffers::grpc::Message<Stat> *,
+                     ::grpc::ClientWriteReactor<flatbuffers::grpc::Message<
+                         Monster> > *)>(&Stub::async_GetMaxHitPoint))>::value,
+    "Client streaming reactor async_GetMaxHitPoint missing");
+static_assert(std::is_member_function_pointer<
+                  decltype(static_cast<void (Stub::*)(
+                               ::grpc::ClientContext *,
+                               ::grpc::ClientBidiReactor<
+                                   flatbuffers::grpc::Message<Monster>,
+                                   flatbuffers::grpc::Message<Stat> > *)>(
+                      &Stub::async_GetMinMaxHitPoints))>::value,
+              "Bidi streaming reactor async_GetMinMaxHitPoints missing");
+#endif  // FLATBUFFERS_GENERATED_GRPC_CALLBACK_API &&
+        // GRPC_CALLBACK_API_NONEXPERIMENTAL
+
+int main() { return 0; }

grpc/tests/grpctest_callback_compile.cpp

@@ -0,0 +1,22 @@
+#include "monster_test.grpc.fb.h"
+
+// This test only verifies that the generated CallbackService compiles when the
+// callback API is available. It does not run any RPCs.
+
+#if defined(FLATBUFFERS_GENERATED_GRPC_CALLBACK_API) && \
+    defined(GRPC_CALLBACK_API_NONEXPERIMENTAL)
+class CallbackServiceImpl
+    : public MyGame::Example::MonsterStorage::CallbackService {
+ public:
+  // For brevity we don't override methods; user code will provide reactors.
+};
+#endif
+
+int main() {
+#if defined(FLATBUFFERS_GENERATED_GRPC_CALLBACK_API) && \
+    defined(GRPC_CALLBACK_API_NONEXPERIMENTAL)
+  CallbackServiceImpl svc;
+  (void)svc;  // suppress unused
+#endif
+  return 0;
+}