Switch to hslua-2.0

The new HsLua version takes a somewhat different approach to marshalling
and unmarshalling, relying less on typeclasses and more on specialized
types. This allows for better performance and improved error messages.

Furthermore, new abstractions allow to document the code and exposed
functions.

1 files changed, 20 insertions, 17 deletions

diff --git a/src/Text/Pandoc/Lua/Init.hs b/src/Text/Pandoc/Lua/Init.hs
index 94691666c..a9c3695a4 100644
--- a/src/Text/Pandoc/Lua/Init.hs
+++ b/src/Text/Pandoc/Lua/Init.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE OverloadedStrings #-}
 {- |
    Module      : Text.Pandoc.Lua
    Copyright   : Copyright © 2017-2021 Albert Krewinkel
@@ -13,23 +14,23 @@ module Text.Pandoc.Lua.Init
   ) where
 
 import Control.Monad (when)
-import Control.Monad.Catch (try)
+import Control.Monad.Catch (throwM, try)
 import Control.Monad.Trans (MonadIO (..))
 import Data.Data (Data, dataTypeConstrs, dataTypeOf, showConstr)
-import Foreign.Lua (Lua)
+import HsLua as Lua hiding (status, try)
 import GHC.IO.Encoding (getForeignEncoding, setForeignEncoding, utf8)
-import Text.Pandoc.Class.PandocMonad (readDataFile, PandocMonad)
-import Text.Pandoc.Error (PandocError)
+import Text.Pandoc.Class.PandocMonad (PandocMonad, readDataFile)
+import Text.Pandoc.Error (PandocError (PandocLuaError))
 import Text.Pandoc.Lua.Packages (installPandocPackageSearcher)
 import Text.Pandoc.Lua.PandocLua (PandocLua, liftPandocLua, runPandocLua)
-import Text.Pandoc.Lua.Util (throwTopMessageAsError')
-import qualified Foreign.Lua as Lua
+import qualified Data.Text as T
 import qualified Text.Pandoc.Definition as Pandoc
 import qualified Text.Pandoc.Lua.Module.Pandoc as ModulePandoc
 
 -- | Run the lua interpreter, using pandoc's default way of environment
 -- initialization.
-runLua :: (PandocMonad m, MonadIO m) => Lua a -> m (Either PandocError a)
+runLua :: (PandocMonad m, MonadIO m)
+       => LuaE PandocError a -> m (Either PandocError a)
 runLua luaOp = do
   enc <- liftIO $ getForeignEncoding <* setForeignEncoding utf8
   res <- runPandocLua . try $ do
@@ -52,9 +53,9 @@ initLuaState = do
     ModulePandoc.pushModule
     -- register as loaded module
     liftPandocLua $ do
-      Lua.pushvalue Lua.stackTop
-      Lua.getfield Lua.registryindex Lua.loadedTableRegistryField
-      Lua.setfield (Lua.nthFromTop 2) "pandoc"
+      Lua.pushvalue Lua.top
+      Lua.getfield Lua.registryindex Lua.loaded
+      Lua.setfield (Lua.nth 2) "pandoc"
       Lua.pop 1
     -- copy constructors into registry
     putConstructorsInRegistry
@@ -65,10 +66,12 @@ initLuaState = do
   loadInitScript scriptFile = do
     script <- readDataFile scriptFile
     status <- liftPandocLua $ Lua.dostring script
-    when (status /= Lua.OK) . liftPandocLua $
-      throwTopMessageAsError'
-      (("Couldn't load '" ++ scriptFile ++ "'.\n") ++)
-
+    when (status /= Lua.OK) . liftPandocLua $ do
+      err <- popException
+      let prefix = "Couldn't load '" <> T.pack scriptFile <> "':\n"
+      throwM . PandocLuaError . (prefix <>) $ case err of
+        PandocLuaError msg -> msg
+        _                  -> T.pack $ show err
 
 -- | AST elements are marshaled via normal constructor functions in the
 -- @pandoc@ module. However, accessing Lua globals from Haskell is
@@ -91,12 +94,12 @@ putConstructorsInRegistry = liftPandocLua $ do
   putInReg "List"  -- pandoc.List
   putInReg "SimpleTable"  -- helper for backward-compatible table handling
  where
-  constrsToReg :: Data a => a -> Lua ()
+  constrsToReg :: Data a => a -> LuaE PandocError ()
   constrsToReg = mapM_ (putInReg . showConstr) . dataTypeConstrs . dataTypeOf
 
-  putInReg :: String -> Lua ()
+  putInReg :: String -> LuaE PandocError ()
   putInReg name = do
     Lua.push ("pandoc." ++ name) -- name in registry
     Lua.push name -- in pandoc module
-    Lua.rawget (Lua.nthFromTop 3)
+    Lua.rawget (Lua.nth 3)
     Lua.rawset Lua.registryindex