ORC-2013: [C++][FOLLOWUP] Better CMake integration with Apache Arrow

Author: wgtmac

cmake_modules/ThirdpartyToolchain.cmake

@@ -172,6 +172,12 @@ elseif (ORC_PACKAGE_KIND STREQUAL "vcpkg")
   list (APPEND ORC_SYSTEM_DEPENDENCIES Protobuf)
   list (APPEND ORC_INSTALL_INTERFACE_TARGETS "$<INSTALL_INTERFACE:protobuf::libprotobuf>")
   set (PROTOBUF_EXECUTABLE protobuf::protoc)
+elseif (TARGET ${ARROW_PROTOBUF_LIBPROTOBUF})
+  # Used by Apache Arrow only, remove this once Arrow leverages FetchContent for Protobuf
+  add_library (orc_protobuf INTERFACE IMPORTED)
+  target_link_libraries(orc_protobuf INTERFACE ${ARROW_PROTOBUF_LIBPROTOBUF})
+  set (PROTOBUF_EXECUTABLE ${ARROW_PROTOBUF_PROTOC})
+  message(STATUS "Using existing ${ARROW_PROTOBUF_LIBPROTOBUF}")
 elseif (NOT "${PROTOBUF_HOME}" STREQUAL "")
   find_package (ProtobufAlt REQUIRED)
 
@@ -181,12 +187,6 @@ elseif (NOT "${PROTOBUF_HOME}" STREQUAL "")
     orc_add_resolved_library (orc_protobuf ${PROTOBUF_LIBRARY} ${PROTOBUF_INCLUDE_DIR})
   endif ()
 
-  if (ORC_PREFER_STATIC_PROTOBUF AND PROTOC_STATIC_LIB)
-    orc_add_resolved_library (orc_protoc ${PROTOC_STATIC_LIB} ${PROTOBUF_INCLUDE_DIR})
-  else ()
-    orc_add_resolved_library (orc_protoc ${PROTOC_LIBRARY} ${PROTOBUF_INCLUDE_DIR})
-  endif ()
-
   list (APPEND ORC_SYSTEM_DEPENDENCIES ProtobufAlt)
   list (APPEND ORC_INSTALL_INTERFACE_TARGETS "$<INSTALL_INTERFACE:protobuf::libprotobuf>")
   orc_provide_find_module (ProtobufAlt)
@@ -245,7 +245,10 @@ else ()
 
     add_library(orc_protobuf INTERFACE IMPORTED)
     target_link_libraries(orc_protobuf INTERFACE protobuf::libprotobuf)
-    set(PROTOBUF_EXECUTABLE protobuf::protoc)
+    # Sometimes downstream environments (e.g. conda) need to override PROTOBUF_EXECUTABLE
+    if(NOT PROTOBUF_EXECUTABLE)
+      set(PROTOBUF_EXECUTABLE protobuf::protoc)
+    endif()
   endblock()
 endif ()
 
@@ -275,6 +278,16 @@ elseif (NOT "${SNAPPY_HOME}" STREQUAL "")
   list (APPEND ORC_SYSTEM_DEPENDENCIES SnappyAlt)
   list (APPEND ORC_INSTALL_INTERFACE_TARGETS "$<INSTALL_INTERFACE:Snappy::snappy>")
   orc_provide_find_module (SnappyAlt)
+elseif (TARGET Snappy::snappy)
+  # Used by Apache Arrow only, remove this once Arrow leverages FetchContent for Snappy
+  add_library (orc_snappy INTERFACE IMPORTED)
+  target_link_libraries(orc_snappy INTERFACE Snappy::snappy)
+  message(STATUS "Using existing Snappy::snappy")
+elseif (TARGET Snappy::snappy-static)
+  # Used by Apache Arrow only, remove this once Arrow leverages FetchContent for Snappy
+  add_library (orc_snappy INTERFACE IMPORTED)
+  target_link_libraries(orc_snappy INTERFACE Snappy::snappy-static)
+  message(STATUS "Using existing Snappy::snappy-static")
 else ()
   block(PROPAGATE ORC_SYSTEM_DEPENDENCIES ORC_INSTALL_INTERFACE_TARGETS)
     prepare_fetchcontent()
@@ -357,6 +370,11 @@ elseif (NOT "${ZLIB_HOME}" STREQUAL "")
   list (APPEND ORC_SYSTEM_DEPENDENCIES ZLIBAlt)
   list (APPEND ORC_INSTALL_INTERFACE_TARGETS "$<INSTALL_INTERFACE:ZLIB::ZLIB>")
   orc_provide_find_module (ZLIBAlt)
+elseif (TARGET ZLIB::ZLIB)
+  # Used by Apache Arrow only, remove this once Arrow leverages FetchContent for ZLIB
+  add_library (orc_zlib INTERFACE IMPORTED)
+  target_link_libraries(orc_zlib INTERFACE ZLIB::ZLIB)
+  message(STATUS "Using existing ZLIB::ZLIB")
 else ()
   block(PROPAGATE ORC_SYSTEM_DEPENDENCIES ORC_INSTALL_INTERFACE_TARGETS ZLIB_LIBRARIES ZLIB_INCLUDE_DIRS)
     prepare_fetchcontent()
@@ -448,6 +466,16 @@ elseif (NOT "${ZSTD_HOME}" STREQUAL "")
   endif ()
   list (APPEND ORC_SYSTEM_DEPENDENCIES ZSTDAlt)
   orc_provide_find_module (ZSTDAlt)
+elseif (TARGET zstd::libzstd_shared)
+  # Used by Apache Arrow only, remove this once Arrow leverages FetchContent for zstd
+  add_library (orc_zstd INTERFACE IMPORTED)
+  target_link_libraries(orc_zstd INTERFACE zstd::libzstd_shared)
+  message(STATUS "Using existing zstd::libzstd_shared")
+elseif (TARGET zstd::libzstd_static)
+  # Used by Apache Arrow only, remove this once Arrow leverages FetchContent for zstd
+  add_library (orc_zstd INTERFACE IMPORTED)
+  target_link_libraries(orc_zstd INTERFACE zstd::libzstd_static)
+  message(STATUS "Using existing zstd::libzstd_static")
 else ()
   block(PROPAGATE ORC_SYSTEM_DEPENDENCIES ORC_INSTALL_INTERFACE_TARGETS)
     prepare_fetchcontent()