[ARROW-10011] [C++] Make FindRE2.cmake re-entrant

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.0.0, 1.0.1
• Fix Version/s: 2.0.0
• Component/s: C++, FlightRPC
• Labels: pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/26035
• Assignee: Uwe Korn
• Reporter: Uwe Korn
• Created: 15/Sep/20 07:48
• Updated: 11/Jan/23 08:10
• Resolved: 15/Sep/20 10:17

Description

Repeated calls to FindRE2.cmake try to recreate the exisiting target RE2::re2 which is prohibited by CMake and fails with the following error:

CMake Warning (dev) at C:/Miniconda37-x64/envs/arrow/Library/share/cmake-3.17/Modules/FindPackageHandleStandardArgs.cmake:272 (message):
  The package name passed to `find_package_handle_standard_args` (RE2) does
  not match the name of the calling package (re2).  This can lead to problems
  in calling code that expects `find_package` result variables (e.g.,
  `_FOUND`) to follow a certain pattern.
Call Stack (most recent call first):
  cmake_modules/FindRE2.cmake:63 (find_package_handle_standard_args)
  C:/Miniconda37-x64/envs/arrow/Library/lib/cmake/grpc/gRPCConfig.cmake:21 (find_package)
  cmake_modules/ThirdpartyToolchain.cmake:2472 (find_package)
  CMakeLists.txt:495 (include)
This warning is for project developers.  Use -Wno-dev to suppress it.
CMake Error at cmake_modules/FindRE2.cmake:66 (add_library):
  add_library cannot create imported target "RE2::re2" because another target
  with the same name already exists.
Call Stack (most recent call first):
  C:/Miniconda37-x64/envs/arrow/Library/lib/cmake/grpc/gRPCConfig.cmake:21 (find_package)
  cmake_modules/ThirdpartyToolchain.cmake:2472 (find_package)
  CMakeLists.txt:495 (include)

Note that this issue only occurs currently on case-insensitive file systems when ARROW_FLIGHT=ON is set.

Issue Links

• links to: GitHub Pull Request #8192