ax_lua.m4: Add 5th argument to make LuaJIT option configurable

m4/ax_lua.m4

@@ -4,7 +4,9 @@
 #
 # SYNOPSIS
 #
-#   AX_PROG_LUA[([MINIMUM-VERSION], [TOO-BIG-VERSION], [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])]
+#   AX_PROG_LUA[([MINIMUM-VERSION], [TOO-BIG-VERSION],
+#                [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND],
+#                [ENABLE_LUAJIT])]
 #   AX_LUA_HEADERS[([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])]
 #   AX_LUA_LIBS[([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])]
 #   AX_LUA_READLINE[([ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])]
@@ -49,20 +51,22 @@
 #   interpreter. If LUA is blank, the user's path is searched for an
 #   suitable interpreter.
 #
-#   Optionally a LUAJIT option may be set ahead of time to look for and
-#   validate a LuaJIT install instead of PUC Lua. Usage might look like:
-#
-#     AC_ARG_WITH(luajit, [AS_HELP_STRING([--with-luajit],
-#         [Prefer LuaJIT over PUC Lua, even if the latter is newer. Default: no])
-#     ])
-#     AM_CONDITIONAL([LUAJIT], [test "x$with_luajit" != 'xno'])
-#
 #   If MINIMUM-VERSION is supplied, then only Lua interpreters with a
 #   version number greater or equal to MINIMUM-VERSION will be accepted. If
 #   TOO-BIG-VERSION is also supplied, then only Lua interpreters with a
 #   version number greater or equal to MINIMUM-VERSION and less than
 #   TOO-BIG-VERSION will be accepted.
 #
+#   Optionally, the fifth argument ENABLE_LUAJIT can be set to control whether
+#   LuaJIT or PUC Lua should be considered during discovery. An empty value or
+#   'never' means only PUC Lua installations will be considered; a value of
+#   'always' means PUC is not even considered and only LuaJIT is discovered;
+#   'prefer' means LuaJIT should be used if found but allow PUC , and finally
+#   'allow' means it should not be chosen if any PUC Lua version is found but
+#   it could be used as a last resort. For 'default' and 'allow' a new
+#   configure flag will be provided to the user --with-luajit with the default
+#   option being either 'yes' or 'no' respectively.
+#
 #   The Lua version number, LUA_VERSION, is found from the interpreter, and
 #   substituted. LUA_PLATFORM is also found, but not currently supported (no
 #   standard representation).
@@ -190,11 +194,12 @@
 #   modified version of the Autoconf Macro, you may extend this special
 #   exception to the GPL to apply to your modified version as well.
 
-#serial 47
+#serial 48
 
 dnl =========================================================================
 dnl AX_PROG_LUA([MINIMUM-VERSION], [TOO-BIG-VERSION],
-dnl             [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND])
+dnl             [ACTION-IF-FOUND], [ACTION-IF-NOT-FOUND]
+dnl             [ENABLE_LUAJIT])
 dnl =========================================================================
 AC_DEFUN([AX_PROG_LUA],
 [
@@ -205,10 +210,36 @@ AC_DEFUN([AX_PROG_LUA],
   dnl Make LUA a precious variable.
   AC_ARG_VAR([LUA], [The Lua interpreter, e.g. /usr/bin/lua5.1])
 
+  dnl Figure out whether we should expose LuaJIT as a user facing configure
+  dnl flag and if so whether the default option should be with or without.
+  AS_CASE(["m4_default([$5], [never])"],
+    [never], [ default_luajit=no; with_luajit=no ],
+    [always], [ default_luajit=yes; with_luajit=yes ],
+    [allow], [
+      default_luajit=no
+      m4_if([$5], [allow], [
+        AC_ARG_WITH([luajit],
+          [AS_HELP_STRING([--with-luajit],
+            [prefer LuaJIT over PUC Lua, even if the latter is newer])])
+        ])
+      test "x$with_luajit" != 'xyes' && with_luajit=no
+    ],
+    [prefer], [
+      default_luajit=yes
+      m4_if([$5], [prefer], [
+        AC_ARG_WITH([luajit],
+          [AS_HELP_STRING([--without-luajit],
+            [prefer PUC Lua over LuaJIT])])
+        ])
+      test "x$with_luajit" != 'xno' && with_luajit=yes
+    ],
+    [AC_MSG_ERROR([Unrecognized value for ENABLE_LUAJIT])])
+  AM_CONDITIONAL([LUAJIT], [test "x$with_luajit" == "xyes"])
+
   dnl Find a Lua interpreter.
   AM_COND_IF([LUAJIT],
-        [_ax_lua_interpreter_list='luajit luajit-2.1.0-beta3 luajit-2.0.5 luajit-2.0.4 luajit-2.0.3'],
-        [_ax_lua_interpreter_list='lua lua5.4 lua54 lua5.3 lua53 lua5.2 lua52 lua5.1 lua51 lua5.0 lua50'])
+    [_ax_lua_interpreter_list='luajit luajit-2.1.0-beta3 luajit-2.0.5 luajit-2.0.4 luajit-2.0.3'],
+    [_ax_lua_interpreter_list='lua lua5.4 lua54 lua5.3 lua53 lua5.2 lua52 lua5.1 lua51 lua5.0 lua50'])
 
   m4_if([$1], [],
   [ dnl No version check is needed. Find any Lua interpreter.