[c++] Add CMake support for pre-installed gRPC

Some systems have a pre-installed gRPC library that they would like to use,
but Bond always builds gRPC from its submodule.

Add the CMake variable `BOND_FIND_GRPC` so that an external gRPC
installation can be used.

Co-authored-by: Christopher Warrington <chwarr@microsoft.com>

Author: bhardwajs

CHANGELOG.md

@@ -20,6 +20,9 @@ different versioning scheme, following the Haskell community's
 
 ### C++/Python ###
 
+* Added CMake variable `BOND_FIND_GRPC` to allow for external gRPC
+  installations. The search for external GRPC installations is only done
+  when `BOND_ENABLE_GRPC` is `TRUE`.
 * Removed use of deprecated `std::ptr_fun` in the Python library. ([Issue
   \#1080](https://github.com/microsoft/bond/issues/1080))
 

CMakeLists.txt

@@ -16,9 +16,12 @@ set (CMAKE_MODULE_PATH
 set (BOND_ENABLE_GRPC
     "TRUE"
     CACHE BOOL "If FALSE, then do not build gRPC integration")
+set (BOND_FIND_GRPC
+    "FALSE"
+    CACHE BOOL "If TRUE, search for an installed gRPC library; if FALSE, then build and use gRPC from the /thirdparty subdirectory")
 set (BOND_FIND_RAPIDJSON
     "FALSE"
-    CACHE BOOL "If FALSE, then use and install rapidjson from thirdparty subdirectory")
+    CACHE BOOL "If FALSE, then use and install rapidjson from the /thirdparty subdirectory")
 # We need to include third-party CMake modules before we configure our own
 # settings so that we don't apply our settings to third-party code.
 add_subdirectory (thirdparty)

examples/cpp/grpc/async-server/CMakeLists.txt

@@ -2,4 +2,9 @@ add_bond_test (grpc-async-server async-server.bond async-server.cpp GRPC)
 
 cxx_target_compile_definitions (MSVC grpc-async-server PRIVATE -D_WIN32_WINNT=0x0600)
 
-target_link_libraries(grpc-async-server PRIVATE grpc++)
+if (BOND_FIND_GRPC)
+    find_package(grpc CONFIG REQUIRED)
+    target_link_libraries(grpc-async-server PRIVATE gRPC::grpc++)
+else ()
+    target_link_libraries(grpc-async-server PRIVATE grpc++)
+endif ()

examples/cpp/grpc/grpc_dll/CMakeLists.txt

@@ -14,8 +14,16 @@ target_compile_definitions (grpc_dll_example_lib PRIVATE -DBUILDING_DLLEXAMPLE_D
 
 add_target_to_folder (grpc_dll_example_lib)
 
+if (BOND_FIND_GRPC)
+    find_package(grpc CONFIG REQUIRED)
+    target_link_libraries(grpc_dll_example_lib PUBLIC
+        gRPC::grpc++)
+else ()
+    target_link_libraries(grpc_dll_example_lib PUBLIC
+        grpc++)
+endif ()
+
 target_link_libraries (grpc_dll_example_lib PUBLIC
-    grpc++
     bond)
 
 cxx_target_compile_definitions (MSVC grpc_dll_example_lib PRIVATE

examples/cpp/grpc/grpc_static_library/CMakeLists.txt

@@ -10,8 +10,16 @@ add_library (grpc_static_library_lib EXCLUDE_FROM_ALL
 
 add_target_to_folder (grpc_static_library_lib)
 
+if (BOND_FIND_GRPC)
+    find_package(grpc CONFIG REQUIRED)
+    target_link_libraries (grpc_static_library_lib PUBLIC
+        gRPC::grpc++)
+else ()
+    target_link_libraries (grpc_static_library_lib PUBLIC
+        grpc++)
+endif ()
+
 target_link_libraries (grpc_static_library_lib PUBLIC
-    grpc++
     bond)
 
 add_bond_test (grpc_static_library_server

examples/cpp/grpc/helloworld/CMakeLists.txt

@@ -2,4 +2,9 @@ add_bond_test (grpc-helloworld helloworld.bond helloworld.cpp GRPC)
 
 cxx_target_compile_definitions (MSVC grpc-helloworld PRIVATE -D_WIN32_WINNT=0x0600)
 
-target_link_libraries(grpc-helloworld PRIVATE grpc++)
+if (BOND_FIND_GRPC)
+    find_package(grpc CONFIG REQUIRED)
+    target_link_libraries(grpc-helloworld PRIVATE gRPC::grpc++)
+else ()
+    target_link_libraries(grpc-helloworld PRIVATE grpc++)
+endif ()

examples/cpp/grpc/pingpong/CMakeLists.txt

@@ -2,4 +2,9 @@ add_bond_test (grpc-pingpong pingpong.bond pingpong.cpp GRPC)
 
 cxx_target_compile_definitions (MSVC grpc-pingpong PRIVATE -D_WIN32_WINNT=0x0600)
 
-target_link_libraries(grpc-pingpong PRIVATE grpc++)
+if (BOND_FIND_GRPC)
+    find_package(grpc CONFIG REQUIRED)
+    target_link_libraries(grpc-pingpong PRIVATE gRPC::grpc++)
+else ()
+    target_link_libraries(grpc-pingpong PRIVATE grpc++)
+endif ()

examples/cpp/grpc/scalar/CMakeLists.txt

@@ -2,4 +2,9 @@ add_bond_test (grpc-scalar scalar.bond scalar.cpp GRPC)
 
 cxx_target_compile_definitions (MSVC grpc-scalar PRIVATE -D_WIN32_WINNT=0x0600)
 
-target_link_libraries(grpc-scalar PRIVATE grpc++)
+if (BOND_FIND_GRPC)
+    find_package(grpc CONFIG REQUIRED)
+    target_link_libraries(grpc-scalar PRIVATE gRPC::grpc++)
+else ()
+    target_link_libraries(grpc-scalar PRIVATE grpc++)
+endif ()

thirdparty/CMakeLists.txt

@@ -1,6 +1,10 @@
 include (Compiler)
 
 if (BOND_ENABLE_GRPC)
-    cxx_add_compile_options (Clang -Wno-unused-value)
-    add_subdirectory(grpc)
-endif()
+    if (BOND_FIND_GRPC)
+        find_package(grpc CONFIG REQUIRED)
+    else ()
+        cxx_add_compile_options(Clang -Wno-unused-value)
+        add_subdirectory(grpc)
+    endif ()
+endif ()