Missing find_dependency() when OTel plugin is enabled

[coryan]

What version of gRPC and what language are you using?

1.63.0, C++.

What operating system (Linux, Windows,...) and version?

Linux

What runtime / compiler are you using (e.g. python version or version of gcc)

Many, but let's say Clang 18 and GCC 14.

What did you do?

Compiled gRPC with:

curl -fsSL https://github.com/grpc/grpc/archive/v1.63.0.tar.gz | \
    tar -xzf - --strip-components=1 && \
    cmake \
      -DCMAKE_BUILD_TYPE=Release \
      -DBUILD_SHARED_LIBS=ON \
      -DgRPC_INSTALL=ON \
      -DgRPC_BUILD_TESTS=OFF \
      -DgRPC_ABSL_PROVIDER=package \
      -DgRPC_CARES_PROVIDER=package \
      -DgRPC_PROTOBUF_PROVIDER=package \
      -DgRPC_PROTOBUF_PACKAGE_TYPE=CONFIG \
      -DgRPC_RE2_PROVIDER=package \
      -DgRPC_SSL_PROVIDER=package \
      -DgRPC_ZLIB_PROVIDER=package \
      -DgRPC_OPENTELEMETRY_PROVIDER=package \
      -DgRPC_BUILD_GRPCPP_OTEL_PLUGIN=ON \
      -GNinja -S . -B cmake-out && \
    cmake --build cmake-out --target install && \
    ldconfig && cd /var/tmp && rm -fr build

Then try to use find_package(gRPC CONFIG REQUIRED)

What did you expect to see?

The gRPC package successfully found.

What did you see instead?

CMake Error at /usr/local/lib/cmake/grpc/gRPCTargets.cmake:223 (set_target_properties):
  The link interface of target "gRPC::grpcpp_otel_plugin" contains:

    opentelemetry-cpp::api

  but the target was not found.  Possible reasons include:

    * There is a typo in the target name.
    * A find_package call is missing for an IMPORTED target.
    * An ALIAS target is missing.

Call Stack (most recent call first):
  /usr/local/lib/cmake/grpc/gRPCConfig.cmake:24 (include)
  cmake/FindgRPC.cmake:116 (find_package)
  CMakeLists.txt:205 (find_package)

I think the grpCConfig.cmake file is missing a find_dependency(opentelemetry-cpp) when gRPC is compiled with the OTel plugin enabled.

Anything else we should know about your project / environment?

You know where to find me.

[yashykt]

Hmm, I don't understand. It's present at

grpc/cmake/opentelemetry-cpp.cmake

Line 42 in fb6a57b

find_package(opentelemetry-cpp CONFIG REQUIRED)

and our example builds as well

[coryan]

When somebody is trying to use an installed version gRPC the grpc/cmake/opentelemetry-cpp.cmake file has no effect. That file is not even installed. As part of make install (or cmake --install) gRPC creates a CMake configuration file:

ls -l /usr/local/lib/cmake/grpc/gRPCConfig.cmake 

That file should list all the dependencies for all the targets, but it does not:

$ cat /usr/local/lib/cmake/grpc/gRPCConfig.cmake 
# Module path
list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR}/modules)

# Depend packages
if(NOT ZLIB_FOUND)
  find_package(ZLIB)
endif()
include(CMakeFindDependencyMacro)
find_dependency(Protobuf CONFIG)
if(NOT OPENSSL_FOUND)
  find_package(OpenSSL)
endif()
if(NOT c-ares_FOUND)
  find_package(c-ares)
endif()
if(NOT TARGET absl::strings)
  find_package(absl CONFIG)
endif()
if(NOT re2_FOUND)
  find_package(re2)
endif()

# Targets
include(${CMAKE_CURRENT_LIST_DIR}/gRPCTargets.cmake)
if(NOT CMAKE_CROSSCOMPILING)
  include(${CMAKE_CURRENT_LIST_DIR}/gRPCPluginTargets.cmake)
endif()

[yashykt]

Thanks for the details! @coryan