cmake: refactor searching libraries and executable

There are three ways to set Lua libraries, headers and executable:

1. Setting CMake option ENABLE_LUAJIT will trigger searching LuaJIT
   library, headers and executable.
2. Setting CMake options LUA_LIBRARIES, LUA_INCLUDE_DIR and
   optional LUA_EXECUTABLE with a path Lua library, directory with
   headers and to a path to Lua executable explicitly.
3. Searching PUC Rio Lua library, headers and executable
   automatically.

LUA_EXECUTABLE is required for regression testing only, so if this
CMake variable was not specified explicitly or was not found
automatically the testing will not be enabled.

The patch simplify a code for searching Lua library and makes the
behavior the same for all three cases described above:

- Move a code for searching `luajit` binary executable to CMake
  module.
- Remove fatal message for a case when PUC Rio Lua executable
  was not found.
- Remove excess `unset()` for ENABLE_TESTING.

Needed for #59

Author: ligurio

CMakeLists.txt

@@ -24,27 +24,24 @@ if(LUA_INCLUDE_DIR AND LUA_LIBRARIES)
   set_target_properties(liblua PROPERTIES
     IMPORTED_LOCATION ${LUA_LIBRARIES})
   set(LUA_LIBRARIES liblua)
+  set(LUA_FOUND TRUE)
 elseif(ENABLE_LUAJIT)
-  include(FindLuaJIT)
-  set(LUA_NAME "luajit")
-  find_program(LUA_EXECUTABLE "${LUA_NAME}")
-  if(NOT EXISTS ${LUA_EXECUTABLE})
-    message(FATAL_ERROR "`${LUA_NAME}` is required")
-  endif()
+  find_package(LuaJIT)
   set(LUA_HAS_JIT ON CACHE INTERNAL "Use LuaJIT library")
   message(STATUS "Found LuaJIT ${LUA_VERSION_STRING}")
   message(STATUS "Found LuaJIT interpreter ${LUA_EXECUTABLE}")
 else()
   find_package(Lua 5.1 REQUIRED)
   set(LUA_NAME "lua${LUA_VERSION_MAJOR}.${LUA_VERSION_MINOR}")
   find_program(LUA_EXECUTABLE "${LUA_NAME}")
-  if(NOT EXISTS ${LUA_EXECUTABLE})
-    message(FATAL_ERROR "${LUA_NAME} is required")
-  endif()
   message(STATUS "Found Lua ${LUA_VERSION_STRING}")
   message(STATUS "Found Lua interpreter ${LUA_EXECUTABLE}")
 endif()
 
+if(NOT LUA_FOUND)
+  message(FATAL_ERROR "Lua library is not found")
+endif()
+
 if(LUAJIT_FRIENDLY_MODE AND NOT LUA_HAS_JIT)
   message(FATAL_ERROR "LuaJIT-friendly mode requires option ENABLE_LUAJIT")
 endif()
@@ -66,7 +63,6 @@ endif()
 
 if(ENABLE_TESTING AND NOT EXISTS ${LUA_EXECUTABLE})
   message(WARNING "Lua executable is not found, testing is not available.")
-  unset(ENABLE_TESTING)
 else()
   enable_testing()
 endif()

cmake/FindLuaJIT.cmake

@@ -1,9 +1,10 @@
-# Locate a LuaJIT library.
+# Locate a LuaJIT library and binary executable.
 #
 # This module defines:
 #  LUA_FOUND, if false, do not try to link to LuaJIT,
 #  LUA_LIBRARIES, where to find libluajit,
 #  LUA_INCLUDE_DIR, where to find luajit.h,
+#  LUA_EXECUTABLE, where to find luajit binary executable,
 #  LUA_VERSION_STRING, the version of LuaJIT found,
 #  LUA_VERSION_MAJOR, the major version of LuaJIT,
 #  LUA_VERSION_MINOR, the minor version of LuaJIT,
@@ -41,13 +42,21 @@ find_package_handle_standard_args(LuaJIT
   VERSION_VAR LUA_VERSION_STRING
   FAIL_MESSAGE "${ERROR_MESSAGE}"
 )
-# Set LUA_FOUND, LUA_INCLUDE_DIR and LUA_LIBRARIES for
-# compatibility with FindLua.cmake.
+
+find_program(LUAJIT_EXECUTABLE luajit)
+if(NOT EXISTS ${LUAJIT_EXECUTABLE})
+  message(WARNING "`luajit` is not found")
+endif()
+
+# Set LUA_FOUND, LUA_INCLUDE_DIR, LUA_LIBRARIES and LUA_EXECUTABLE
+# for compatibility with FindLua.cmake.
 set(LUA_FOUND ${LUAJIT_FOUND})
 set(LUA_LIBRARIES ${LUAJIT_LIBRARIES})
 set(LUA_INCLUDE_DIR ${LUAJIT_INCLUDE_DIR})
+set(LUA_EXECUTABLE ${LUAJIT_EXECUTABLE})
 unset(LUAJIT_FOUND)
 unset(LUAJIT_LIBRARIES)
 unset(LUAJIT_INCLUDE_DIR)
+unset(LUAJIT_EXECUTABLE)
 
 mark_as_advanced(LUA_INCLUDE_DIR LUA_LIBRARIES)