Include Lua version in --version output. (#7997)

src/Text/Pandoc/App/CommandLineOptions.hs

@@ -4,6 +4,7 @@
 {-# LANGUAGE TupleSections       #-}
 {-# LANGUAGE OverloadedStrings   #-}
 {-# LANGUAGE FlexibleContexts    #-}
+{-# LANGUAGE TypeApplications    #-}
 {- |
    Module      : Text.Pandoc.App.CommandLineOptions
    Copyright   : Copyright (C) 2006-2022 John MacFarlane
@@ -37,6 +38,7 @@ import Data.List (isPrefixOf)
 #endif
 import Data.Maybe (fromMaybe, isJust)
 import Data.Text (Text)
+import HsLua (Exception, getglobal, openlibs, peek, run, top)
 import Safe (tailDef)
 import Skylighting (Style, Syntax (..), defaultSyntaxMap, parseTheme)
 import System.Console.GetOpt
@@ -946,10 +948,14 @@ options =
                   (\_ -> do
                      prg <- getProgName
                      defaultDatadir <- defaultUserDataDir
+                     luaVersion <- HsLua.run @HsLua.Exception $ do
+                       openlibs
+                       getglobal "_VERSION"
+                       peek top
                      UTF8.hPutStrLn stdout
                       $ T.pack
                       $ prg ++ " " ++ T.unpack pandocVersion ++
-                        compileInfo ++
+                        compileInfo ++ "\nScripting engine: " ++ luaVersion ++
                         "\nUser data directory: " ++ defaultDatadir ++
                         ('\n':copyrightMessage)
                      exitSuccess ))