CMake/Modules/FindLua.cmake

# Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
# file LICENSE.rst or https://cmake.org/licensing for details.

#[=======================================================================[.rst:
FindLua
-------

Finds the Lua library.  Lua is a embeddable scripting language.

.. versionadded:: 3.18
  Support for Lua 5.4.

When working with Lua, its library headers are intended to be included in
project source code as:

.. code-block:: c

  #include <lua.h>

and not:

.. code-block:: c

  #include <lua/lua.h>

This is because, the location of Lua headers may differ across platforms and may
exist in locations other than ``lua/``.

Result Variables
^^^^^^^^^^^^^^^^

This module defines the following variables:

``Lua_FOUND``
  Boolean indicating whether (the requested version of) Lua is found.  For
  backward compatibility, the ``LUA_FOUND`` variable is also set to the same
  value.
``LUA_VERSION_STRING``
  The version of Lua found.
``LUA_VERSION_MAJOR``
  The major version of Lua found.
``LUA_VERSION_MINOR``
  The minor version of Lua found.
``LUA_VERSION_PATCH``
  The patch version of Lua found.
``LUA_LIBRARIES``
  Libraries needed to link against to use Lua.  This list includes both ``lua``
  and ``lualib`` libraries.

Cache Variables
^^^^^^^^^^^^^^^

The following cache variables may also be set:

``LUA_INCLUDE_DIR``
  The directory containing the Lua header files, such as ``lua.h``,
  ``lualib.h``, and ``lauxlib.h``, needed to use Lua.

Examples
^^^^^^^^

Finding the Lua library and creating an interface :ref:`imported target
<Imported Targets>` that encapsulates its usage requirements for linking to a
project target:

.. code-block:: cmake

  find_package(Lua)

  if(Lua_FOUND AND NOT TARGET Lua::Lua)
    add_library(Lua::Lua INTERFACE IMPORTED)
    set_target_properties(
      Lua::Lua
      PROPERTIES
        INTERFACE_INCLUDE_DIRECTORIES "${LUA_INCLUDE_DIR}"
        INTERFACE_LINK_LIBRARIES "${LUA_LIBRARIES}"
    )
  endif()

  target_link_libraries(project_target PRIVATE Lua::Lua)
#]=======================================================================]

cmake_policy(PUSH)  # Policies apply to functions at definition-time
cmake_policy(SET CMP0159 NEW)  # file(STRINGS) with REGEX updates CMAKE_MATCH_<n>

unset(_lua_include_subdirs)
unset(_lua_library_names)
unset(_lua_append_versions)

# this is a function only to have all the variables inside go away automatically
function(_lua_get_versions)
    set(LUA_VERSIONS5 5.4 5.3 5.2 5.1 5.0)

    if (Lua_FIND_VERSION_EXACT)
        if (Lua_FIND_VERSION_COUNT GREATER 1)
            set(_lua_append_versions ${Lua_FIND_VERSION_MAJOR}.${Lua_FIND_VERSION_MINOR})
        endif ()
    elseif (Lua_FIND_VERSION)
        # once there is a different major version supported this should become a loop
        if (NOT Lua_FIND_VERSION_MAJOR GREATER 5)
            if (Lua_FIND_VERSION_COUNT EQUAL 1)
                set(_lua_append_versions ${LUA_VERSIONS5})
            else ()
                foreach (subver IN LISTS LUA_VERSIONS5)
                    if (NOT subver VERSION_LESS ${Lua_FIND_VERSION})
                        list(APPEND _lua_append_versions ${subver})
                    endif ()
                endforeach ()
                # New version -> Search for it (heuristic only! Defines in include might have changed)
                if (NOT _lua_append_versions)
                    set(_lua_append_versions ${Lua_FIND_VERSION_MAJOR}.${Lua_FIND_VERSION_MINOR})
                endif()
            endif ()
        endif ()
    else ()
        # once there is a different major version supported this should become a loop
        set(_lua_append_versions ${LUA_VERSIONS5})
    endif ()

    if (LUA_Debug)
        message(STATUS "Considering following Lua versions: ${_lua_append_versions}")
    endif()

    set(_lua_append_versions "${_lua_append_versions}" PARENT_SCOPE)
endfunction()

function(_lua_set_version_vars)
  set(_lua_include_subdirs_raw "lua")

  foreach (ver IN LISTS _lua_append_versions)
    string(REGEX MATCH "^([0-9]+)\\.([0-9]+)$" _ver "${ver}")
    list(APPEND _lua_include_subdirs_raw
        lua${CMAKE_MATCH_1}${CMAKE_MATCH_2}
        lua${CMAKE_MATCH_1}.${CMAKE_MATCH_2}
        lua-${CMAKE_MATCH_1}.${CMAKE_MATCH_2}
        )
  endforeach ()

  # Prepend "include/" to each path directly after the path
  set(_lua_include_subdirs "include")
  foreach (dir IN LISTS _lua_include_subdirs_raw)
    list(APPEND _lua_include_subdirs "${dir}" "include/${dir}")
  endforeach ()

  set(_lua_include_subdirs "${_lua_include_subdirs}" PARENT_SCOPE)
endfunction()

function(_lua_get_header_version)
  unset(LUA_VERSION_STRING PARENT_SCOPE)
  set(_hdr_file "${LUA_INCLUDE_DIR}/lua.h")

  if (NOT EXISTS "${_hdr_file}")
    return()
  endif ()

  # At least 5.[012] have different ways to express the version
  # so all of them need to be tested. Lua 5.2 defines LUA_VERSION
  # and LUA_RELEASE as joined by the C preprocessor, so avoid those.
  file(STRINGS "${_hdr_file}" lua_version_strings
       REGEX "^#define[ \t]+LUA_(RELEASE[ \t]+\"Lua [0-9]|VERSION([ \t]+\"Lua [0-9]|_[MR])).*")

  string(REGEX REPLACE ".*;#define[ \t]+LUA_VERSION_MAJOR[ \t]+\"([0-9])\"[ \t]*;.*" "\\1" LUA_VERSION_MAJOR ";${lua_version_strings};")
  if (LUA_VERSION_MAJOR MATCHES "^[0-9]+$")
    string(REGEX REPLACE ".*;#define[ \t]+LUA_VERSION_MINOR[ \t]+\"([0-9])\"[ \t]*;.*" "\\1" LUA_VERSION_MINOR ";${lua_version_strings};")
    string(REGEX REPLACE ".*;#define[ \t]+LUA_VERSION_RELEASE[ \t]+\"([0-9])\"[ \t]*;.*" "\\1" LUA_VERSION_PATCH ";${lua_version_strings};")
    set(LUA_VERSION_STRING "${LUA_VERSION_MAJOR}.${LUA_VERSION_MINOR}.${LUA_VERSION_PATCH}")
  else ()
    string(REGEX REPLACE ".*;#define[ \t]+LUA_RELEASE[ \t]+\"Lua ([0-9.]+)\"[ \t]*;.*" "\\1" LUA_VERSION_STRING ";${lua_version_strings};")
    if (NOT LUA_VERSION_STRING MATCHES "^[0-9.]+$")
      string(REGEX REPLACE ".*;#define[ \t]+LUA_VERSION[ \t]+\"Lua ([0-9.]+)\"[ \t]*;.*" "\\1" LUA_VERSION_STRING ";${lua_version_strings};")
    endif ()
    string(REGEX REPLACE "^([0-9]+)\\.[0-9.]*$" "\\1" LUA_VERSION_MAJOR "${LUA_VERSION_STRING}")
    string(REGEX REPLACE "^[0-9]+\\.([0-9]+)[0-9.]*$" "\\1" LUA_VERSION_MINOR "${LUA_VERSION_STRING}")
    string(REGEX REPLACE "^[0-9]+\\.[0-9]+\\.([0-9]).*" "\\1" LUA_VERSION_PATCH "${LUA_VERSION_STRING}")
  endif ()
  foreach (ver IN LISTS _lua_append_versions)
    if (ver STREQUAL "${LUA_VERSION_MAJOR}.${LUA_VERSION_MINOR}")
      set(LUA_VERSION_MAJOR ${LUA_VERSION_MAJOR} PARENT_SCOPE)
      set(LUA_VERSION_MINOR ${LUA_VERSION_MINOR} PARENT_SCOPE)
      set(LUA_VERSION_PATCH ${LUA_VERSION_PATCH} PARENT_SCOPE)
      set(LUA_VERSION_STRING ${LUA_VERSION_STRING} PARENT_SCOPE)
      return()
    endif ()
  endforeach ()
endfunction()

function(_lua_find_header)
  _lua_set_version_vars()

  # Initialize as local variable
  set(CMAKE_IGNORE_PATH ${CMAKE_IGNORE_PATH})
  while (TRUE)
    # Find the next header to test. Check each possible subdir in order
    # This prefers e.g. higher versions as they are earlier in the list
    # It is also consistent with previous versions of FindLua
    foreach (subdir IN LISTS _lua_include_subdirs)
      find_path(LUA_INCLUDE_DIR lua.h
        HINTS ENV LUA_DIR
        PATH_SUFFIXES ${subdir}
        )
      if (LUA_INCLUDE_DIR)
        break()
      endif()
    endforeach()
    # Did not found header -> Fail
    if (NOT LUA_INCLUDE_DIR)
      return()
    endif()
    _lua_get_header_version()
    # Found accepted version -> Ok
    if (LUA_VERSION_STRING)
      if (LUA_Debug)
        message(STATUS "Found suitable version ${LUA_VERSION_STRING} in ${LUA_INCLUDE_DIR}/lua.h")
      endif()
      return()
    endif()
    # Found wrong version -> Ignore this path and retry
    if (LUA_Debug)
      message(STATUS "Ignoring unsuitable version in ${LUA_INCLUDE_DIR}")
    endif()
    list(APPEND CMAKE_IGNORE_PATH "${LUA_INCLUDE_DIR}")
    unset(LUA_INCLUDE_DIR CACHE)
    unset(LUA_INCLUDE_DIR)
    unset(LUA_INCLUDE_DIR PARENT_SCOPE)
  endwhile ()
endfunction()

_lua_get_versions()
_lua_find_header()
_lua_get_header_version()
unset(_lua_append_versions)

if (LUA_VERSION_STRING)
  set(_lua_library_names
    lua${LUA_VERSION_MAJOR}${LUA_VERSION_MINOR}
    lua${LUA_VERSION_MAJOR}.${LUA_VERSION_MINOR}
    lua-${LUA_VERSION_MAJOR}.${LUA_VERSION_MINOR}
    lua.${LUA_VERSION_MAJOR}.${LUA_VERSION_MINOR}
    )
endif ()

find_library(LUA_LIBRARY
  NAMES ${_lua_library_names} lua
  NAMES_PER_DIR
  HINTS
    ENV LUA_DIR
  PATH_SUFFIXES lib
)
unset(_lua_library_names)

if (LUA_LIBRARY)
  # include the math library for Unix
  if (UNIX AND NOT APPLE AND NOT BEOS)
    find_library(LUA_MATH_LIBRARY m)
    mark_as_advanced(LUA_MATH_LIBRARY)
    set(LUA_LIBRARIES "${LUA_LIBRARY};${LUA_MATH_LIBRARY}")

    # include dl library for statically-linked Lua library
    get_filename_component(LUA_LIB_EXT ${LUA_LIBRARY} EXT)
    if(LUA_LIB_EXT STREQUAL CMAKE_STATIC_LIBRARY_SUFFIX)
      list(APPEND LUA_LIBRARIES ${CMAKE_DL_LIBS})
    endif()

  # For Windows and Mac, don't need to explicitly include the math library
  else ()
    set(LUA_LIBRARIES "${LUA_LIBRARY}")
  endif ()
endif ()

include(FindPackageHandleStandardArgs)
find_package_handle_standard_args(Lua
                                  REQUIRED_VARS LUA_LIBRARIES LUA_INCLUDE_DIR
                                  VERSION_VAR LUA_VERSION_STRING)

mark_as_advanced(LUA_INCLUDE_DIR LUA_LIBRARY)

cmake_policy(POP)