pandoc-cli: Allow building a binary without Lua support

Disabling the `lua` cabal flag will result in a binary without Lua.

1 files changed, 35 insertions, 0 deletions

diff --git a/pandoc-cli/lua/PandocCLI/Lua.hs b/pandoc-cli/lua/PandocCLI/Lua.hs
new file mode 100644
index 000000000..6507587c8
--- /dev/null
+++ b/pandoc-cli/lua/PandocCLI/Lua.hs
@@ -0,0 +1,35 @@
+{-# LANGUAGE OverloadedStrings #-}
+{- |
+   Module      : PandocCLI.Lua
+   Copyright   : © 2022 Albert Krewinkel
+   License     : GPL-2.0-or-later
+   Maintainer  : Albert Krewinkel <[email protected]>
+
+Functions to run the pandoc Lua scripting engine.
+-}
+module PandocCLI.Lua (runLuaInterpreter, getEngine) where
+
+import Control.Monad ((<=<))
+import HsLua.CLI (EnvBehavior (..), Settings (..), runStandalone)
+import Text.Pandoc.Class (runIOorExplode)
+import Text.Pandoc.Error (handleError)
+import Text.Pandoc.Lua (runLua, runLuaNoEnv, getEngine)
+import Text.Pandoc.Shared (pandocVersionText)
+
+-- | Runs pandoc as a Lua interpreter that is (mostly) compatible with
+-- the default @lua@ program shipping with Lua.
+runLuaInterpreter :: String    -- ^ Program name
+                  -> [String]  -- ^ Command line arguments
+                  -> IO ()
+runLuaInterpreter progName args = do
+  let settings = Settings
+        { settingsVersionInfo = "\nEmbedded in pandoc " <> pandocVersionText
+        , settingsRunner = runner
+        }
+  runStandalone settings progName args
+  where
+    runner envBehavior =
+      let runLua' = case envBehavior of
+                      IgnoreEnvVars  -> runLuaNoEnv
+                      ConsultEnvVars -> runLua
+      in handleError <=< runIOorExplode . runLua'