update(build): fallback to manually find libraries when grpc config c…

…make module is not found on system.

Ubuntu focal is not shipping the module. Avoid breaking CI and builds on it.

Signed-off-by: Federico Di Pierro <nierro92@gmail.com>

cmake/modules/grpc.cmake

@@ -4,24 +4,54 @@ if(GRPC_INCLUDE)
 	# we already have grpc
 elseif(NOT USE_BUNDLED_GRPC)
 	# gRPC
-	find_package(gRPC CONFIG REQUIRED)
-	message(STATUS "Using gRPC ${gRPC_VERSION}")
-	set(GPR_LIB gRPC::gpr)
-	set(GRPC_LIB gRPC::grpc)
-	set(GRPCPP_LIB gRPC::grpc++)
+	find_package(gRPC CONFIG)
+	if(gRPC_FOUND)
+		message(STATUS "Using gRPC ${gRPC_VERSION}")
+		set(GPR_LIB gRPC::gpr)
+		set(GRPC_LIB gRPC::grpc)
+		set(GRPCPP_LIB gRPC::grpc++)
 
-	# # gRPC C++ plugin
-	get_target_property(GRPC_CPP_PLUGIN gRPC::grpc_cpp_plugin LOCATION)
-	if(NOT GRPC_CPP_PLUGIN)
-		message(FATAL_ERROR "System grpc_cpp_plugin not found")
-	endif()
+		# # gRPC C++ plugin
+		get_target_property(GRPC_CPP_PLUGIN gRPC::grpc_cpp_plugin LOCATION)
+		if(NOT GRPC_CPP_PLUGIN)
+			message(FATAL_ERROR "System grpc_cpp_plugin not found")
+		endif()
 
-	# gRPC include dir + properly handle grpc{++,pp}
-	get_target_property(GRPC_INCLUDE gRPC::grpc++ INTERFACE_INCLUDE_DIRECTORIES)
-	find_path(GRPCXX_INCLUDE NAMES grpc++/grpc++.h)
-	if(NOT GRPCXX_INCLUDE)
-		find_path(GRPCPP_INCLUDE NAMES grpcpp/grpcpp.h)
-		add_definitions(-DGRPC_INCLUDE_IS_GRPCPP=1)
+		# gRPC include dir + properly handle grpc{++,pp}
+		get_target_property(GRPC_INCLUDE gRPC::grpc++ INTERFACE_INCLUDE_DIRECTORIES)
+		find_path(GRPCXX_INCLUDE NAMES grpc++/grpc++.h)
+		if(NOT GRPCXX_INCLUDE)
+			find_path(GRPCPP_INCLUDE NAMES grpcpp/grpcpp.h)
+			add_definitions(-DGRPC_INCLUDE_IS_GRPCPP=1)
+		endif()
+	else()
+		# Fallback to manually find libraries;
+		# Some distro, namely Ubuntu focal, do not install gRPC config cmake module
+		find_library(GPR_LIB NAMES gpr)
+		if(GPR_LIB)
+			message(STATUS "Found gpr lib: ${GPR_LIB}")
+		else()
+			message(FATAL_ERROR "Couldn't find system gpr")
+		endif()
+		find_path(GRPCXX_INCLUDE NAMES grpc++/grpc++.h)
+		if(GRPCXX_INCLUDE)
+			set(GRPC_INCLUDE ${GRPCXX_INCLUDE})
+		else()
+			find_path(GRPCPP_INCLUDE NAMES grpcpp/grpcpp.h)
+			set(GRPC_INCLUDE ${GRPCPP_INCLUDE})
+			add_definitions(-DGRPC_INCLUDE_IS_GRPCPP=1)
+		endif()
+		find_library(GRPC_LIB NAMES grpc)
+		find_library(GRPCPP_LIB NAMES grpc++)
+		if(GRPC_INCLUDE AND GRPC_LIB AND GRPCPP_LIB)
+			message(STATUS "Found grpc: include: ${GRPC_INCLUDE}, C lib: ${GRPC_LIB}, C++ lib: ${GRPCPP_LIB}")
+		else()
+			message(FATAL_ERROR "Couldn't find system grpc")
+		endif()
+		find_program(GRPC_CPP_PLUGIN grpc_cpp_plugin)
+		if(NOT GRPC_CPP_PLUGIN)
+			message(FATAL_ERROR "System grpc_cpp_plugin not found")
+		endif()
 	endif()
 else()
 	include(cares)