Tests/RunCMake/find_file/Optional.cmake - external/github.com/Kitware/CMake - Git at Google

 set(CMAKE_FIND_REQUIRED ON)
 find_file(FILE_doNotExists_Optional
   NAMES doNotExists.h
   OPTIONAL
 )
 find_file(FILE_doNotExists_OptionalRequired
   NAMES doNotExists.h
   OPTIONAL
   REQUIRED
 )
 find_file(FILE_doNotExists
   NAMES doNotExists.h
   REQUIRED
 )
	set(CMAKE_FIND_REQUIRED ON)
	find_file(FILE_doNotExists_Optional
	NAMES doNotExists.h
	OPTIONAL
	)
	find_file(FILE_doNotExists_OptionalRequired
	NAMES doNotExists.h
	OPTIONAL
	REQUIRED
	)
	find_file(FILE_doNotExists
	NAMES doNotExists.h
	REQUIRED
	)