[clangd] Fix remote index build for macOS with Homebrew-installed gRPC and Protobuf

[sammccall]

llvm/cmake/modules/FindGRPC.cmake

26

how does the conditional logic/recovery around this work?
e.g. what if it's installed in the system, but not via homebrew? What if homebrew is available, but grpc or protobuf are not installed?

[kbobyrev]

llvm/cmake/modules/FindGRPC.cmake

26

For now, there is no recovery or workaround. The only way to have system-installed install grpc + protobuf other than Homebrew would probably be compiling and doing make install but I don't think people are happy with doing that (and if they are already building it then it'd be better to use GRPC_INSTALL_PATH). Homebrew is de-facto the standard package manager for macOS and while I could check if Homebrew is found and if the packages are install and fall back to the "default" case when if they aren't we assume gRPC headers, libraries and binaries are all in the search paths I think that would be optimising for weird setups nobody is likely to use.

WDYT?

[kbobyrev]

Recover when Homebrew is not a available or gRPC + Protobuf are not installed through Homebrew.

[kbobyrev]

Rebase on top of master.

[sammccall]

llvm/cmake/modules/FindGRPC.cmake

26

This could use some comments, "fall back to homebrew-installed libraries, which typically aren't on the system path."

26

this block should only run if we didn't already find the proto tools, right?

57

at this point it would be nice to have have a cmake check that protoc and grpc_cpp_plugin both exist, and that we can include the proto and grpc headers.
This would ensure we get errors at configure time instead of build time.

(unrelated though, separate change if you want to do this)

[kbobyrev]

Resolve review comments.

llvm/cmake/modules/FindGRPC.cmake

26

Not really, the proto tools are in $PATH, but include directories and libraries aren't in default search paths.

57

Good point! I've added a check for protoc and grpc_cpp_plugin and a FIXME regarding the ability to include headers. I'll do that in a separate patch.

[kbobyrev]

systtem -> system

llvm/cmake/modules/FindGRPC.cmake

 # This setup requires gRPC to be built from sources using CMake and installed to
 # ${GRPC_INSTALL_PATH} via -DCMAKE_INSTALL_PREFIX=${GRPC_INSTALL_PATH}.
+# FIXME(kirillbobyrev): Check if gRPC and Protobuf headers can be included at
+# configure time.
 if (GRPC_INSTALL_PATH)
   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})
 
   # 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)
   add_library(protobuf ALIAS protobuf::libprotobuf)
   set_target_properties(gRPC::grpc++ PROPERTIES IMPORTED_GLOBAL TRUE)
   add_library(grpc++ ALIAS gRPC::grpc++)
 
   set(GRPC_CPP_PLUGIN $<TARGET_FILE:gRPC::grpc_cpp_plugin>)
   set(PROTOC ${Protobuf_PROTOC_EXECUTABLE})
 else()
   find_program(GRPC_CPP_PLUGIN grpc_cpp_plugin)
   find_program(PROTOC protoc)
+  if (GRPC_CPP_PLUGIN-NOTFOUND OR PROTOC-NOTFOUND)
+    message(FATAL_ERROR "gRPC C++ Plugin and Protoc must be on $PATH for Clangd remote index build")
+  endif()
+  # On macOS the libraries are typically installed via Homebrew and are not on
+  # the system path.
+  if (${APPLE})
+    find_program(HOMEBREW brew)
+    # If Homebrew is not found, the user might have installed libraries
+    # manually. Fall back to the system path.
+    if (NOT HOMEBREW-NOTFOUND)
+      execute_process(COMMAND ${HOMEBREW} --prefix grpc
+        OUTPUT_VARIABLE GRPC_HOMEBREW_PATH
+        RESULT_VARIABLE GRPC_HOMEBREW_RETURN_CODE
+        OUTPUT_STRIP_TRAILING_WHITESPACE)
+      execute_process(COMMAND ${HOMEBREW} --prefix protobuf
+        OUTPUT_VARIABLE PROTOBUF_HOMEBREW_PATH
+        RESULT_VARIABLE PROTOBUF_HOMEBREW_RETURN_CODE
+        OUTPUT_STRIP_TRAILING_WHITESPACE)
+      # If either library is not installed via Homebrew, fall back to the
+      # system path.
+      if (GRPC_HOMEBREW_RETURN_CODE EQUAL "0")
+        include_directories(${GRPC_HOMEBREW_PATH}/include)
+        link_directories(${GRPC_HOMEBREW_PATH}/lib)
+      endif()
+      if (PROTOBUF_HOMEBREW_RETURN_CODE EQUAL "0")
+        include_directories(${PROTOBUF_HOMEBREW_PATH}/include)
+        link_directories(${PROTOBUF_HOMEBREW_PATH}/lib)
+      endif()
+    endif()
+  endif()
 endif()
 
 # Proto headers are generated in ${CMAKE_CURRENT_BINARY_DIR}.
 # Libraries that use these headers should adjust the include path.
 # FIXME(kirillbobyrev): Allow optional generation of gRPC code and give callers
 # control over it via additional parameters.
 function(generate_grpc_protos LibraryName ProtoFile)
   get_filename_component(ProtoSourceAbsolutePath "${CMAKE_CURRENT_SOURCE_DIR}/${ProtoFile}" ABSOLUTE)
   get_filename_component(ProtoSourcePath ${ProtoSourceAbsolutePath} PATH)