System-wide libedit not found on macOS

[Nicogene]

@claudiofantacci reported:

Describe the bug macOS comes with a system-wide libedit located in /usr/local that is usually found by CMake and used, e.g., to enhance the UX of YARP RPC ports (command line like input, tokenization, etc.). System-wide libedit is no longer found by CMake and the only way to get it trough is to install libedit with brew and to force link it brew install libedit && brew link --force libedit.

To Reproduce Configure YARP with Xcode version 9+. I'm not sure how Xcode actually as an impact on this, and in particular with CMake, but this correlation is also confirmed by our Travis builds:

• Master
  • Compiled with Xcode 8.3 - Found
  • Compiled with Xcode 9.4 - Not found
• Devel
  • Compiled with Xcode 8.3 - Found
  • Compiled with Xcode 9.4 - Not found

Expected behavior System-wide libedit found without the need to force link libedit under brew.

Configuration (please complete the following information):

• OS: 10.13.4
• yarp version: 3.1.100+20180802.3+git013120125
• compiler: Apple LLVM version 9.0.0 (clang-900.0.39.2)

Additional context My only guess so far is that by upgrading to Xcode 9+ the (possibly present, I can't check it) pkg-config libedit.pc has been removed and the standard_find_module (invoked here) is no longer able to find the library. As a matter of the fact, by force linking libedit with brew, standard_find_module indeed finds the libedit.pc that is shipped with it.

Additional comments As a matter of the fact/consequence, the Travis command related to brew install libedit is useless unless it is brew link --force libedit. By checking the Travis log it is clearly reported that the formula is keg-only, i.e. it is not symlinked because libedit is shipped with the OS.

[claudiofantacci]

Original post https://github.com/robotology/yarp/issues/1829#issuecomment-412502099

Ok, I might have missed a bit the "stack" for the cmake calls.

Then, yes. I can confirm that the .pc has been removed as I triggered it 🤣 IMHO there is no need to use the brew version, but we should create the FindLibedit.cmake to handle the case where the system provides the library.