Custom writer: use init file to setup Lua interpreter

The same init file (`data/init`) that is used to setup the Lua
interpreter for Lua filters is also used to setup the interpreter of
custom writers.lua.

4 files changed, 106 insertions, 55 deletions

diff --git a/src/Text/Pandoc/App.hs b/src/Text/Pandoc/App.hs
index f7d6450cc..e70b606a9 100644
--- a/src/Text/Pandoc/App.hs
+++ b/src/Text/Pandoc/App.hs
@@ -223,7 +223,7 @@ convertWithOpts opts = do
             if ".lua" `isSuffixOf` format
                -- note:  use non-lowercased version writerName
                then return (TextWriter
-                       (\o d -> liftIO $ writeCustom writerName o d)
+                       (\o d -> writeCustom writerName o d)
                                :: Writer PandocIO, mempty)
                else case getWriter writerName of
                          Left e  -> E.throwIO $ PandocAppError $
@@ -846,7 +846,7 @@ applyLuaFilters :: Maybe FilePath -> [FilePath] -> String -> Pandoc
 applyLuaFilters mbDatadir filters format d = do
   expandedFilters <- mapM (expandFilterPath mbDatadir) filters
   let go f d' = do
-        res <- runLuaFilter mbDatadir f format d'
+        res <- runLuaFilter f format d'
         case res of
           Right x               -> return x
           Left (LuaException s) -> E.throw (PandocFilterError f s)
diff --git a/src/Text/Pandoc/Lua.hs b/src/Text/Pandoc/Lua.hs
index 696f4de44..a56e89511 100644
--- a/src/Text/Pandoc/Lua.hs
+++ b/src/Text/Pandoc/Lua.hs
@@ -27,43 +27,32 @@ Running pandoc Lua filters.
 -}
 module Text.Pandoc.Lua
   ( LuaException (..)
-  , LuaPackageParams (..)
-  , pushPandocModule
   , runLuaFilter
-  , initLuaState
-  , luaPackageParams
+  , runPandocLua
+  , pushPandocModule
   ) where
 
 import Control.Monad (when, (>=>))
-import Control.Monad.Trans (MonadIO (..))
-import Data.IORef (newIORef, readIORef)
 import Foreign.Lua (FromLuaStack (peek), Lua, LuaException (..),
                     Status (OK), ToLuaStack (push))
-import Text.Pandoc.Class (PandocIO, getCommonState, getMediaBag, setMediaBag)
-import Text.Pandoc.Definition
+import Text.Pandoc.Class (PandocIO)
+import Text.Pandoc.Definition (Pandoc)
 import Text.Pandoc.Lua.Filter (LuaFilter, walkMWithLuaFilter)
-import Text.Pandoc.Lua.Packages (LuaPackageParams (..),
-                                 installPandocPackageSearcher)
+import Text.Pandoc.Lua.Init (runPandocLua)
 import Text.Pandoc.Lua.PandocModule (pushPandocModule) -- TODO: remove
-import Text.Pandoc.Lua.Util (loadScriptFromDataDir)
 import qualified Foreign.Lua as Lua
-import qualified Foreign.Lua.Module.Text as Lua
 
-runLuaFilter :: Maybe FilePath -> FilePath -> String
+-- | Run the Lua filter in @filterPath@ for a transformation to target
+-- format @format@. Pandoc uses Lua init files to setup the Lua
+-- interpreter.
+runLuaFilter :: FilePath -> String
              -> Pandoc -> PandocIO (Either LuaException Pandoc)
-runLuaFilter datadir filterPath format pd = do
-  luaPkgParams <- luaPackageParams datadir
-  res <- liftIO . Lua.runLuaEither $
-         runLuaFilter' luaPkgParams filterPath format pd
-  newMediaBag <- liftIO (readIORef (luaPkgMediaBag luaPkgParams))
-  setMediaBag newMediaBag
-  return res
+runLuaFilter filterPath format doc =
+  runPandocLua (runLuaFilter' filterPath format doc)
 
-runLuaFilter' :: LuaPackageParams
-              -> FilePath -> String
+runLuaFilter' :: FilePath -> String
               -> Pandoc -> Lua Pandoc
-runLuaFilter' luaPkgOpts filterPath format pd = do
-  initLuaState luaPkgOpts
+runLuaFilter' filterPath format pd = do
   -- store module in global "pandoc"
   registerFormat
   top <- Lua.gettop
@@ -83,24 +72,6 @@ runLuaFilter' luaPkgOpts filterPath format pd = do
     push format
     Lua.setglobal "FORMAT"
 
-luaPackageParams :: Maybe FilePath -> PandocIO LuaPackageParams
-luaPackageParams datadir = do
-  commonState <- getCommonState
-  mbRef <- liftIO . newIORef =<< getMediaBag
-  return LuaPackageParams
-    { luaPkgCommonState = commonState
-    , luaPkgDataDir = datadir
-    , luaPkgMediaBag = mbRef
-    }
-
--- Initialize the lua state with all required values
-initLuaState :: LuaPackageParams -> Lua ()
-initLuaState luaPkgParams = do
-  Lua.openlibs
-  Lua.preloadTextModule "text"
-  installPandocPackageSearcher luaPkgParams
-  loadScriptFromDataDir (luaPkgDataDir luaPkgParams) "init.lua"
-
 pushGlobalFilter :: Lua ()
 pushGlobalFilter = do
   Lua.newtable
diff --git a/src/Text/Pandoc/Lua/Init.hs b/src/Text/Pandoc/Lua/Init.hs
new file mode 100644
index 000000000..a2bfa3801
--- /dev/null
+++ b/src/Text/Pandoc/Lua/Init.hs
@@ -0,0 +1,79 @@
+{-
+Copyright © 2017 Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+-}
+{- |
+   Module      : Text.Pandoc.Lua
+   Copyright   : Copyright © 2017 Albert Krewinkel
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+   Stability   : alpha
+
+Functions to initialize the Lua interpreter.
+-}
+module Text.Pandoc.Lua.Init
+  ( LuaException (..)
+  , LuaPackageParams (..)
+  , runPandocLua
+  , initLuaState
+  , luaPackageParams
+  ) where
+
+import Control.Monad.Trans (MonadIO (..))
+import Data.IORef (newIORef, readIORef)
+import Foreign.Lua (Lua, LuaException (..))
+import GHC.IO.Encoding (getForeignEncoding, setForeignEncoding, utf8)
+import Text.Pandoc.Class (PandocIO, getCommonState, getUserDataDir, getMediaBag,
+                          setMediaBag)
+import Text.Pandoc.Lua.Packages (LuaPackageParams (..),
+                                 installPandocPackageSearcher)
+import Text.Pandoc.Lua.Util (loadScriptFromDataDir)
+
+import qualified Foreign.Lua as Lua
+import qualified Foreign.Lua.Module.Text as Lua
+
+-- | Run the lua interpreter, using pandoc's default way of environment
+-- initalization.
+runPandocLua :: Lua a -> PandocIO (Either LuaException a)
+runPandocLua luaOp = do
+  datadir <- getUserDataDir
+  luaPkgParams <- luaPackageParams datadir
+  enc <- liftIO $ getForeignEncoding <* setForeignEncoding utf8
+  res <- liftIO $ Lua.runLuaEither (initLuaState luaPkgParams *> luaOp)
+  liftIO $ setForeignEncoding enc
+  newMediaBag <- liftIO (readIORef (luaPkgMediaBag luaPkgParams))
+  setMediaBag newMediaBag
+  return res
+
+-- | Generate parameters required to setup pandoc's lua environment.
+luaPackageParams :: Maybe FilePath -> PandocIO LuaPackageParams
+luaPackageParams datadir = do
+  commonState <- getCommonState
+  mbRef <- liftIO . newIORef =<< getMediaBag
+  return LuaPackageParams
+    { luaPkgCommonState = commonState
+    , luaPkgDataDir = datadir
+    , luaPkgMediaBag = mbRef
+    }
+
+-- Initialize the lua state with all required values
+initLuaState :: LuaPackageParams -> Lua ()
+initLuaState luaPkgParams = do
+  Lua.openlibs
+  Lua.preloadTextModule "text"
+  installPandocPackageSearcher luaPkgParams
+  loadScriptFromDataDir (luaPkgDataDir luaPkgParams) "init.lua"
diff --git a/src/Text/Pandoc/Writers/Custom.hs b/src/Text/Pandoc/Writers/Custom.hs
index ffe637966..72f443ed0 100644
--- a/src/Text/Pandoc/Writers/Custom.hs
+++ b/src/Text/Pandoc/Writers/Custom.hs
@@ -33,18 +33,20 @@ module Text.Pandoc.Writers.Custom ( writeCustom ) where
 import Control.Arrow ((***))
 import Control.Exception
 import Control.Monad (when)
+import Control.Monad.Trans (MonadIO (liftIO))
 import Data.Char (toLower)
 import Data.List (intersperse)
 import qualified Data.Map as M
 import Data.Text (Text, pack)
 import Data.Typeable
-import Foreign.Lua (Lua, ToLuaStack (..), callFunc, runLua)
+import Foreign.Lua (Lua, ToLuaStack (..), callFunc)
 import Foreign.Lua.Api
-import GHC.IO.Encoding (getForeignEncoding, setForeignEncoding, utf8)
+import Text.Pandoc.Class (PandocIO)
 import Text.Pandoc.Definition
 import Text.Pandoc.Error
+import Text.Pandoc.Lua.Init (runPandocLua)
 import Text.Pandoc.Lua.StackInstances ()
-import Text.Pandoc.Lua.Util (addValue)
+import Text.Pandoc.Lua.Util (addValue, dostring')
 import Text.Pandoc.Options
 import Text.Pandoc.Templates
 import qualified Text.Pandoc.UTF8 as UTF8
@@ -91,14 +93,11 @@ data PandocLuaException = PandocLuaException String
 instance Exception PandocLuaException
 
 -- | Convert Pandoc to custom markup.
-writeCustom :: FilePath -> WriterOptions -> Pandoc -> IO Text
+writeCustom :: FilePath -> WriterOptions -> Pandoc -> PandocIO Text
 writeCustom luaFile opts doc@(Pandoc meta _) = do
-  luaScript <- UTF8.readFile luaFile
-  enc <- getForeignEncoding
-  setForeignEncoding utf8
-  (body, context) <- runLua $ do
-    openlibs
-    stat <- loadstring luaScript
+  luaScript <- liftIO $ UTF8.readFile luaFile
+  res <- runPandocLua $ do
+    stat <- dostring' luaScript
     -- check for error in lua script (later we'll change the return type
     -- to handle this more gracefully):
     when (stat /= OK) $
@@ -111,7 +110,9 @@ writeCustom luaFile opts doc@(Pandoc meta _) = do
                inlineListToCustom
                meta
     return (rendered, context)
-  setForeignEncoding enc
+  let (body, context) = case res of
+        Left e -> throw (PandocLuaException (show e))
+        Right x -> x
   case writerTemplate opts of
        Nothing  -> return $ pack body
        Just tpl ->