Suggestion for generating C++ files using FetchContent's grpc

[Hung Dang]

Hi all,

I use the below CMake script to automatically generate C++ files from a list of proto files using pre-installed gRPC libraries. My approach does not work if grpc is built using CMake's FetchContent, i.e as a sub-module, because CMake could not find the gRPCTargets.cmake file. 

How do you handle this issue in your CMake build?

Thanks,

Hung

f# Use local build gRPC and protobuf libraries

set(EXTERNAL_DIR "${ROOT_DIR}/3p")
if(UNIX AND NOT APPLE)
  set(protobuf_DIR "${EXTERNAL_DIR}/lib64/cmake/protobuf/")
elseif(APPLE)
  set(protobuf_DIR "${EXTERNAL_DIR}/lib/cmake/protobuf/")
elseif(MSVC)
  set(protobuf_DIR "${EXTERNAL_DIR}/cmake/")
else()
  message(FATAL_ERROR "This platform is unsupported. CMake will exit.")
endif()
set(gRPC_DIR "${EXTERNAL_DIR}/lib/cmake/grpc")

find_package(protobuf CONFIG REQUIRED NO_DEFAULT_PATH)
find_package(gRPC CONFIG REQUIRED NO_DEFAULT_PATH)
find_package(Threads)

set(PROTO_FILES address.proto addressbook.proto healthcheck.proto
                helloworld.proto keyvaluestore.proto)

# Add Library target with protobuf sources
add_library(address ${PROTO_FILES})
target_link_libraries(address PUBLIC protobuf::libprotobuf gRPC::grpc
                                     gRPC::grpc++)
target_include_directories(address PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})

# Generate protobuf and grpc C++ files
get_target_property(grpc_cpp_plugin_location gRPC::grpc_cpp_plugin LOCATION)
protobuf_generate(TARGET address LANGUAGE cpp)
protobuf_generate(
  TARGET
  address
  LANGUAGE
  grpc
  GENERATE_EXTENSIONS
  .grpc.pb.h
  .grpc.pb.cc
  PLUGIN
  "protoc-gen-grpc=${grpc_cpp_plugin_location}")