Generate grpc files for a library target in CMAKE - c++

Question

In the following project structure(from my previous question):
root/
├─ CMakeLists.txt
├─ protocol/
│ ├─ msg.proto
│ ├─ myrpc.proto
│ ├─ CMakeLists.txt
├─ app/
│ ├─ main.cpp
│ ├─ CMakeLists.txt
I could generate the protobuf files and add them as dependency into the app target. Now I am trying to generate grpc files inside the same library.
Something is not right with the grpc generation function, which is based on this answer and blog post;as the following error message is printed:
-- Configuring done
-- Generating done
-- Build files have been written to: /media/davids91/Work/rafko/src/main/cxx/build
[ 1%] Running grpc protocol buffer compiler on /usr/local/bin/grpc_cpp_plugin
/usr/local/bin/grpc_cpp_plugin: File does not reside within any path specified using --proto_path (or -I). You must specify a --proto_path which encompasses this file. Note that the proto_path must be an exact prefix of the .proto file names -- protoc is too dumb to figure out when two paths (e.g. absolute and relative) are equivalent (it's harder than you think).
make[2]: * [protocol/CMakeFiles/protocol.dir/build.make:138: /media/usr/local/bin/grpc_cpp_plugin.grpc.pb.h] Error 1
make[1]: * [CMakeFiles/Makefile2:276: protocol/CMakeFiles/protocol.dir/all] Error 2
make: * [Makefile:103: all] Error 2
I can see that the install folder looks correct, as that is where the grpc library was installed from source.
root CMakeLists.txt:
cmake_minimum_required(VERSION 3.18.4)
project(
root
VERSION 0.1
LANGUAGES CXX
)
add_subdirectory(protocol)
add_subdirectory(app)
protocol CMakeLists.txt:
add_library(protocol)
target_include_directories(protocol
PUBLIC
.
${CMAKE_CURRENT_BINARY_DIR}
${Protobuf_INCLUDE_DIRS}
)
find_package(Protobuf REQUIRED)
find_package(gRPC CONFIG REQUIRED)
target_link_libraries(protocol ${Protobuf_LIBRARIES})
get_target_property(grpc_cpp_plugin_location gRPC::grpc_cpp_plugin LOCATION)
protobuf_generate( TARGET protocol LANGUAGE CPP PROTOS msg.proto )
protobuf_generate(
TARGET
protocol
LANGUAGE
grpc
PROTOS
myrpc.proto
PLUGIN
"protoc-gen-grpc=${grpc_cpp_plugin_location}"
)
app CMakeLists.txt:
add_library(app)
target_link_libraries(app PUBLIC protocol)
target_include_directories(app PUBLIC .)
target_sources(app
PRIVATE
main.cpp
)
What might be missing from this solution to generate out the grpc files based on the plugins?

Answer 1

After some experimenting and closely looking at the example here I figured it out!
I updated protocol CMakeLists.txt:
changed
find_package(Protobuf REQUIRED)
to
find_package(Protobuf CONFIG REQUIRED)
I figure it tells CMake that the proto files are being procesed at configuration time, but any deeper explanation is welcome!