Text.Pandoc.Lua: cleanup element walking code

WalkM is general enough to work in any monad, not just IO. Also get rid
of the LuaException type, sufficient to use the one defined in hslua.

1 files changed, 20 insertions, 28 deletions

diff --git a/src/Text/Pandoc/Lua.hs b/src/Text/Pandoc/Lua.hs
index c5770a18b..264364006 100644
--- a/src/Text/Pandoc/Lua.hs
+++ b/src/Text/Pandoc/Lua.hs
@@ -30,33 +30,25 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
 Pandoc lua utils.
 -}
-module Text.Pandoc.Lua ( LuaException(..),
-                         runLuaFilter,
-                         pushPandocModule ) where
+module Text.Pandoc.Lua (LuaException (..), pushPandocModule, runLuaFilter) where
 
-import Control.Exception
 import Control.Monad (unless, when, (>=>), mplus)
 import Control.Monad.Trans (MonadIO (..))
 import Data.Data (toConstr, showConstr, dataTypeOf, dataTypeConstrs, Data)
 import Data.Map (Map)
 import Data.Maybe (isJust)
-import Data.Typeable (Typeable)
-import Foreign.Lua (Lua, FromLuaStack (..), ToLuaStack (..), runLua,
-                    peekEither, getglobal', throwLuaError)
-import Foreign.Lua.Types.Lua (runLuaWith, liftLua1)
-import Foreign.Lua.Api
+import Foreign.Lua (Lua, FromLuaStack (peek), LuaException (..), StackIndex,
+                    Status(OK), ToLuaStack (push), call, isnil, dofile,
+                    getglobal', gettop, isfunction, newtable, openlibs, pcall,
+                    peekEither, pop, pushvalue, rawgeti, rawseti, ref,
+                    registryindex, runLua, setglobal, throwLuaError)
 import Text.Pandoc.Definition
 import Text.Pandoc.Lua.PandocModule (pushPandocModule)
 import Text.Pandoc.Lua.StackInstances ()
-import Text.Pandoc.Walk
+import Text.Pandoc.Walk (Walkable (walkM))
 
 import qualified Data.Map as Map
 
-newtype LuaException = LuaException String
-  deriving (Show, Typeable)
-
-instance Exception LuaException
-
 runLuaFilter :: (MonadIO m)
              => Maybe FilePath -> FilePath -> [String] -> Pandoc -> m Pandoc
 runLuaFilter datadir filterPath args pd = liftIO . runLua $ do
@@ -90,26 +82,26 @@ runAll :: [LuaFilter] -> Pandoc -> Lua Pandoc
 runAll = foldr ((>=>) . walkMWithLuaFilter) return
 
 walkMWithLuaFilter :: LuaFilter -> Pandoc -> Lua Pandoc
-walkMWithLuaFilter (LuaFilter fnMap) = liftLua1 walkLua
+walkMWithLuaFilter (LuaFilter fnMap) = walkLua
   where
-    walkLua :: LuaState -> Pandoc -> IO Pandoc
-    walkLua l =
+    walkLua :: Pandoc -> Lua Pandoc
+    walkLua =
           (if hasOneOf (constructorsFor (dataTypeOf (Str [])))
-           then walkM (runLuaWith l . (tryFilter fnMap :: Inline -> Lua Inline))
+           then walkM (tryFilter fnMap :: Inline -> Lua Inline)
            else return)
           >=>
           (if hasOneOf (constructorsFor (dataTypeOf (Para [])))
-           then walkM ((runLuaWith l . (tryFilter fnMap :: Block -> Lua Block)))
+           then walkM (tryFilter fnMap :: Block -> Lua Block)
            else return)
           >=>
           (case Map.lookup "Meta" fnMap of
-             Just fn -> walkM ((\(Pandoc meta blocks) -> runLuaWith l $ do
-                                     meta' <- runFilterFunction fn meta
-                                     return $ Pandoc meta' blocks))
+             Just fn -> walkM (\(Pandoc meta blocks) -> do
+                                  meta' <- runFilterFunction fn meta
+                                  return $ Pandoc meta' blocks)
              Nothing -> return)
           >=>
           (case Map.lookup "Pandoc" fnMap `mplus` Map.lookup "Doc" fnMap of
-             Just fn -> runLuaWith l . (runFilterFunction fn :: Pandoc -> Lua Pandoc)
+             Just fn -> runFilterFunction fn :: Pandoc -> Lua Pandoc
              Nothing -> return)
     hasOneOf = any (\k -> isJust (Map.lookup k fnMap))
     constructorsFor x = map show (dataTypeConstrs x)
@@ -146,10 +138,10 @@ runFilterFunction lf x = do
       let prefix = "Error while running filter function: "
       throwLuaError $ prefix ++ msg
     else do
-      resType <- ltype (-1)
-      case resType of
-        TypeNil -> pop 1 *> return x
-        _       -> do
+      noExplicitFilter <- isnil (-1)
+      if noExplicitFilter
+        then  pop 1 *> return x
+        else do
           mbres <- peekEither (-1)
           case mbres of
             Left err -> throwLuaError