[CMake][gRPC] Update FindGRPC.cmake to support newer gRPC versions (#162935)

Update the logic to find gRPC to always favor CMake `find_package`
implementation including for builds on macOS that uses homebrew, where
gRPCConfig.cmake is also installed to provide an accurate target
dependencies to link against.

This fixes the problem that newer gRPC version has broken up the
libraries into smaller pieces and the hard coded list of libraries in
the implementation can no longer work.

Fixes: #59844

Author: cachemeifyoucan

cmake/Modules/FindGRPC.cmake

@@ -3,21 +3,23 @@ option(ENABLE_GRPC_REFLECTION "Link to gRPC Reflection library" OFF)
 # FIXME(kirillbobyrev): Check if gRPC and Protobuf headers can be included at
 # configure time.
 find_package(Threads REQUIRED)
-if (GRPC_INSTALL_PATH)
-  # This setup requires gRPC to be built from sources using CMake and installed
-  # to ${GRPC_INSTALL_PATH} via -DCMAKE_INSTALL_PREFIX=${GRPC_INSTALL_PATH}.
-  # Libraries will be linked according to gRPC build policy which generates
-  # static libraries when BUILD_SHARED_LIBS is Off and dynamic libraries when
-  # it's On (NOTE: This is a variable passed to gRPC CMake build invocation,
-  # LLVM's BUILD_SHARED_LIBS has no effect).
-  set(protobuf_MODULE_COMPATIBLE TRUE)
-  find_package(Protobuf CONFIG REQUIRED HINTS ${GRPC_INSTALL_PATH})
-  message(STATUS "Using protobuf ${Protobuf_VERSION}")
-  find_package(gRPC CONFIG REQUIRED HINTS ${GRPC_INSTALL_PATH})
-  message(STATUS "Using gRPC ${gRPC_VERSION}")
 
-  include_directories(${Protobuf_INCLUDE_DIRS})
+# Prefer finding gPRC through CMakeConfig and a hint can be provided via
+# GRPC_INSTALL_PATH. This requires gRPC to be built and installed
+# to ${GRPC_INSTALL_PATH} via -DCMAKE_INSTALL_PREFIX=${GRPC_INSTALL_PATH}.
+# Libraries will be linked according to gRPC build policy which generates
+# static libraries when BUILD_SHARED_LIBS is Off and dynamic libraries when
+# it's On (NOTE: This is a variable passed to gRPC CMake build invocation,
+# LLVM's BUILD_SHARED_LIBS has no effect).
+# Package managers like Homebrew will also install Config.cmake and user can
+# specify GRPC_INSTALL_PATH or CMAKE_PREFIX_PATH to locate installed package.
+set(protobuf_MODULE_COMPATIBLE TRUE)
+find_package(Protobuf CONFIG HINTS ${GRPC_INSTALL_PATH})
+message(STATUS "Using protobuf ${Protobuf_VERSION}")
+find_package(gRPC CONFIG HINTS ${GRPC_INSTALL_PATH})
+message(STATUS "Using gRPC ${gRPC_VERSION}")
 
+if (Protobuf_FOUND AND gRPC_FOUND)
   # gRPC CMake CONFIG gives the libraries slightly odd names, make them match
   # the conventional system-installed names.
   set_target_properties(protobuf::libprotobuf PROPERTIES IMPORTED_GLOBAL TRUE)
@@ -32,10 +34,12 @@ if (GRPC_INSTALL_PATH)
   set(GRPC_CPP_PLUGIN $<TARGET_FILE:gRPC::grpc_cpp_plugin>)
   set(PROTOC ${Protobuf_PROTOC_EXECUTABLE})
 else()
-  # This setup requires system-installed gRPC and Protobuf.
+  # Now fallback to system-installed gRPC and ProtoBuf.
   # We always link dynamically in this mode. While the static libraries are
   # usually installed, the CMake files telling us *which* static libraries to
   # link are not.
+  # FIXME: this path should not work on newer grpc versions and should be
+  # removed in favor of `find_package` implementation.
   if (NOT BUILD_SHARED_LIBS)
     message(NOTICE "gRPC and Protobuf will be linked dynamically. If you want static linking, build gRPC from sources with -DBUILD_SHARED_LIBS=Off.")
   endif()
@@ -44,55 +48,17 @@ else()
   if (NOT GRPC_CPP_PLUGIN OR NOT PROTOC)
     message(FATAL_ERROR "gRPC C++ Plugin and Protoc must be on $PATH for gRPC-enabled build.")
   endif()
-  # On macOS the libraries are typically installed via Homebrew and are not on
-  # the system path.
-  set(GRPC_OPTS "")
-  set(PROTOBUF_OPTS "")
-  set(GRPC_INCLUDE_PATHS "")
-  if (${APPLE})
-    find_program(HOMEBREW brew)
-    # If Homebrew is not found, the user might have installed libraries
-    # manually. Fall back to the system path.
-    if (HOMEBREW)
-      execute_process(COMMAND ${HOMEBREW} --prefix grpc
-        OUTPUT_VARIABLE GRPC_HOMEBREW_PATH
-        RESULT_VARIABLE GRPC_HOMEBREW_RETURN_CODE
-        OUTPUT_STRIP_TRAILING_WHITESPACE)
-      execute_process(COMMAND ${HOMEBREW} --prefix protobuf
-        OUTPUT_VARIABLE PROTOBUF_HOMEBREW_PATH
-        RESULT_VARIABLE PROTOBUF_HOMEBREW_RETURN_CODE
-        OUTPUT_STRIP_TRAILING_WHITESPACE)
-      execute_process(COMMAND ${HOMEBREW} --prefix abseil
-        OUTPUT_VARIABLE ABSL_HOMEBREW_PATH
-        RESULT_VARIABLE ABSL_HOMEBREW_RETURN_CODE
-        OUTPUT_STRIP_TRAILING_WHITESPACE)
-      # If either library is not installed via Homebrew, fall back to the
-      # system path.
-      if (GRPC_HOMEBREW_RETURN_CODE EQUAL "0")
-        list(APPEND GRPC_INCLUDE_PATHS ${GRPC_HOMEBREW_PATH}/include)
-        list(APPEND GRPC_OPTS PATHS ${GRPC_HOMEBREW_PATH}/lib NO_DEFAULT_PATH)
-      endif()
-      if (PROTOBUF_HOMEBREW_RETURN_CODE EQUAL "0")
-        list(APPEND GRPC_INCLUDE_PATHS ${PROTOBUF_HOMEBREW_PATH}/include)
-        list(APPEND PROTOBUF_OPTS PATHS ${PROTOBUF_HOMEBREW_PATH}/lib NO_DEFAULT_PATH)
-      endif()
-      if (ABSL_HOMEBREW_RETURN_CODE EQUAL "0")
-        list(APPEND GRPC_INCLUDE_PATHS ${ABSL_HOMEBREW_PATH}/include)
-      endif()
-    endif()
-  endif()
   if(NOT TARGET grpc++)
-    find_library(GRPC_LIBRARY grpc++ ${GRPC_OPTS} REQUIRED)
+    find_library(GRPC_LIBRARY grpc++ REQUIRED)
     add_library(grpc++ UNKNOWN IMPORTED GLOBAL)
     message(STATUS "Using grpc++: " ${GRPC_LIBRARY})
     set_target_properties(grpc++ PROPERTIES IMPORTED_LOCATION ${GRPC_LIBRARY})
-    target_include_directories(grpc++ INTERFACE ${GRPC_INCLUDE_PATHS})
     if (ENABLE_GRPC_REFLECTION)
-      find_library(GRPC_REFLECTION_LIBRARY grpc++_reflection ${GRPC_OPTS} REQUIRED)
+      find_library(GRPC_REFLECTION_LIBRARY grpc++_reflection REQUIRED)
       add_library(grpc++_reflection UNKNOWN IMPORTED GLOBAL)
       set_target_properties(grpc++_reflection PROPERTIES IMPORTED_LOCATION ${GRPC_REFLECTION_LIBRARY})
     endif()
-    find_library(PROTOBUF_LIBRARY protobuf ${PROTOBUF_OPTS} REQUIRED)
+    find_library(PROTOBUF_LIBRARY protobuf REQUIRED)
     message(STATUS "Using protobuf: " ${PROTOBUF_LIBRARY})
     add_library(protobuf UNKNOWN IMPORTED GLOBAL)
     set_target_properties(protobuf PROPERTIES IMPORTED_LOCATION ${PROTOBUF_LIBRARY})