Text.Pandoc.Lua: move globals handling to separate module

5 files changed, 145 insertions, 69 deletions

diff --git a/pandoc.cabal b/pandoc.cabal
index 975a70d37..682d67c36 100644
--- a/pandoc.cabal
+++ b/pandoc.cabal
@@ -541,6 +541,7 @@ library
                    Text.Pandoc.Writers.Powerpoint.Presentation,
                    Text.Pandoc.Writers.Powerpoint.Output,
                    Text.Pandoc.Lua.Filter,
+                   Text.Pandoc.Lua.Global,
                    Text.Pandoc.Lua.Init,
                    Text.Pandoc.Lua.Module.MediaBag,
                    Text.Pandoc.Lua.Module.Pandoc,
diff --git a/src/Text/Pandoc/Lua.hs b/src/Text/Pandoc/Lua.hs
index e160f7123..de067823f 100644
--- a/src/Text/Pandoc/Lua.hs
+++ b/src/Text/Pandoc/Lua.hs
@@ -37,8 +37,9 @@ import Control.Monad ((>=>))
 import Foreign.Lua (Lua)
 import Text.Pandoc.Class (PandocIO)
 import Text.Pandoc.Definition (Pandoc)
+import Text.Pandoc.Lua.Global (Global (..), setGlobals)
 import Text.Pandoc.Lua.Filter (LuaFilter, walkMWithLuaFilter)
-import Text.Pandoc.Lua.Init (LuaException (..), runPandocLua, registerScriptPath)
+import Text.Pandoc.Lua.Init (LuaException (..), runPandocLua)
 import Text.Pandoc.Lua.Util (dofileWithTraceback)
 import Text.Pandoc.Options (ReaderOptions)
 
@@ -49,15 +50,8 @@ import qualified Foreign.Lua as Lua
 -- interpreter.
 runLuaFilter :: ReaderOptions -> FilePath -> String
              -> Pandoc -> PandocIO (Either LuaException Pandoc)
-runLuaFilter ropts filterPath format doc =
-  runPandocLua (runLuaFilter' ropts filterPath format doc)
-
-runLuaFilter' :: ReaderOptions -> FilePath -> String
-              -> Pandoc -> Lua Pandoc
-runLuaFilter' ropts filterPath format pd = do
-  registerFormat
-  registerReaderOptions
-  registerScriptPath filterPath
+runLuaFilter ropts filterPath format doc = runPandocLua $ do
+  setGlobals globals
   top <- Lua.gettop
   stat <- dofileWithTraceback filterPath
   if stat /= Lua.OK
@@ -69,15 +63,13 @@ runLuaFilter' ropts filterPath format pd = do
       luaFilters <- if newtop - top >= 1
                     then Lua.peek Lua.stackTop
                     else Lua.pushglobaltable *> fmap (:[]) Lua.popValue
-      runAll luaFilters pd
- where
-  registerFormat = do
-    Lua.push format
-    Lua.setglobal "FORMAT"
+      runAll luaFilters doc
 
-  registerReaderOptions = do
-    Lua.push ropts
-    Lua.setglobal "PANDOC_READER_OPTIONS"
+ where
+  globals = [ FORMAT format
+            , PANDOC_READER_OPTIONS ropts
+            , PANDOC_SCRIPT_FILE filterPath
+            ]
 
 runAll :: [LuaFilter] -> Pandoc -> Lua Pandoc
 runAll = foldr ((>=>) . walkMWithLuaFilter) return
diff --git a/src/Text/Pandoc/Lua/Global.hs b/src/Text/Pandoc/Lua/Global.hs
new file mode 100644
index 000000000..237c8b500
--- /dev/null
+++ b/src/Text/Pandoc/Lua/Global.hs
@@ -0,0 +1,108 @@
+{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE NoImplicitPrelude #-}
+{-
+Copyright © 2017-2018 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 © 2017-2018 Albert Krewinkel
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+   Stability   : alpha
+
+Pandoc's Lua globals.
+-}
+module Text.Pandoc.Lua.Global
+  ( Global (..)
+  , setGlobals
+  ) where
+
+import Prelude
+import Data.Data (Data)
+import Data.Version (Version (versionBranch))
+import Foreign.Lua (Lua, Peekable, Pushable)
+import Foreign.Lua.Userdata ( ensureUserdataMetatable, pushAnyWithMetatable
+                            , metatableName)
+import Paths_pandoc (version)
+import Text.Pandoc.Class (CommonState)
+import Text.Pandoc.Definition (Pandoc (Pandoc), pandocTypesVersion)
+import Text.Pandoc.Lua.StackInstances ()
+import Text.Pandoc.Lua.Util (addFunction)
+import Text.Pandoc.Options (ReaderOptions)
+
+import qualified Foreign.Lua as Lua
+
+-- | Permissible global Lua variables.
+data Global =
+    FORMAT String
+  | PANDOC_API_VERSION
+  | PANDOC_DOCUMENT Pandoc
+  | PANDOC_READER_OPTIONS ReaderOptions
+  | PANDOC_SCRIPT_FILE FilePath
+  | PANDOC_STATE CommonState
+  | PANDOC_VERSION
+  -- Cannot derive instance of Data because of CommonState
+
+-- | Set all given globals.
+setGlobals :: [Global] -> Lua ()
+setGlobals = mapM_ setGlobal
+
+setGlobal :: Global -> Lua ()
+setGlobal global = case global of
+  -- This could be simplified if Global was an instance of Data.
+  FORMAT format -> do
+    Lua.push format
+    Lua.setglobal "FORMAT"
+  PANDOC_API_VERSION -> do
+    Lua.push (versionBranch pandocTypesVersion)
+    Lua.setglobal "PANDOC_API_VERSION"
+  PANDOC_DOCUMENT doc -> do
+    Lua.push (LazyPandoc doc)
+    Lua.setglobal "PANDOC_DOCUMENT"
+  PANDOC_READER_OPTIONS ropts -> do
+    Lua.push ropts
+    Lua.setglobal "PANDOC_READER_OPTIONS"
+  PANDOC_SCRIPT_FILE filePath -> do
+    Lua.push filePath
+    Lua.setglobal "PANDOC_SCRIPT_FILE"
+  PANDOC_STATE commonState -> do
+    Lua.push commonState
+    Lua.setglobal "PANDOC_STATE"
+  PANDOC_VERSION              -> do
+    Lua.push (versionBranch version)
+    Lua.setglobal "PANDOC_VERSION"
+
+-- | Readonly and lazy pandoc objects.
+newtype LazyPandoc = LazyPandoc Pandoc
+  deriving (Data)
+
+instance Pushable LazyPandoc where
+  push lazyDoc = pushAnyWithMetatable pushPandocMetatable lazyDoc
+   where
+    pushPandocMetatable = ensureUserdataMetatable (metatableName lazyDoc) $
+                          addFunction "__index" indexLazyPandoc
+
+instance Peekable LazyPandoc where
+  peek = Lua.peekAny
+
+indexLazyPandoc :: LazyPandoc -> String -> Lua Lua.NumResults
+indexLazyPandoc (LazyPandoc (Pandoc meta blks)) field = 1 <$
+  case field of
+    "blocks" -> Lua.push blks
+    "meta"   -> Lua.push meta
+    _        -> Lua.pushnil
diff --git a/src/Text/Pandoc/Lua/Init.hs b/src/Text/Pandoc/Lua/Init.hs
index 78fb6204e..c9ee7267a 100644
--- a/src/Text/Pandoc/Lua/Init.hs
+++ b/src/Text/Pandoc/Lua/Init.hs
@@ -32,20 +32,17 @@ module Text.Pandoc.Lua.Init
   , runPandocLua
   , initLuaState
   , luaPackageParams
-  , registerScriptPath
   ) where
 
 import Prelude
 import Control.Monad.Trans (MonadIO (..))
 import Data.Data (Data, dataTypeConstrs, dataTypeOf, showConstr)
 import Data.IORef (newIORef, readIORef)
-import Data.Version (Version (versionBranch))
 import Foreign.Lua (Lua)
 import GHC.IO.Encoding (getForeignEncoding, setForeignEncoding, utf8)
-import Paths_pandoc (version)
-import Text.Pandoc.Class (CommonState, PandocIO, getCommonState,
-                          getUserDataDir, getMediaBag, setMediaBag)
-import Text.Pandoc.Definition (pandocTypesVersion)
+import Text.Pandoc.Class (PandocIO, getCommonState, getUserDataDir,
+                          getMediaBag, setMediaBag)
+import Text.Pandoc.Lua.Global (Global (..), setGlobals)
 import Text.Pandoc.Lua.Packages (LuaPackageParams (..),
                                  installPandocPackageSearcher)
 import Text.Pandoc.Lua.Util (loadScriptFromDataDir)
@@ -61,11 +58,12 @@ newtype LuaException = LuaException String deriving (Show)
 -- initialization.
 runPandocLua :: Lua a -> PandocIO (Either LuaException a)
 runPandocLua luaOp = do
-  commonState <- getCommonState
   luaPkgParams <- luaPackageParams
+  globals <- defaultGlobals
   enc <- liftIO $ getForeignEncoding <* setForeignEncoding utf8
   res <- liftIO . Lua.runEither $ do
-    initLuaState commonState luaPkgParams
+    setGlobals globals
+    initLuaState luaPkgParams
     luaOp
   liftIO $ setForeignEncoding enc
   newMediaBag <- liftIO (readIORef (luaPkgMediaBag luaPkgParams))
@@ -74,6 +72,16 @@ runPandocLua luaOp = do
     Left (Lua.Exception msg) -> Left (LuaException msg)
     Right x -> Right x
 
+-- | Global variables which should always be set.
+defaultGlobals :: PandocIO [Global]
+defaultGlobals = do
+  commonState <- getCommonState
+  return
+    [ PANDOC_API_VERSION
+    , PANDOC_STATE commonState
+    , PANDOC_VERSION
+    ]
+
 -- | Generate parameters required to setup pandoc's lua environment.
 luaPackageParams :: PandocIO LuaPackageParams
 luaPackageParams = do
@@ -87,25 +95,14 @@ luaPackageParams = do
     }
 
 -- Initialize the lua state with all required values
-initLuaState :: CommonState -> LuaPackageParams -> Lua ()
-initLuaState commonState luaPkgParams = do
+initLuaState :: LuaPackageParams -> Lua ()
+initLuaState luaPkgParams = do
   Lua.openlibs
   Lua.preloadTextModule "text"
-  Lua.push (versionBranch version)
-  Lua.setglobal "PANDOC_VERSION"
-  Lua.push (versionBranch pandocTypesVersion)
-  Lua.setglobal "PANDOC_API_VERSION"
-  Lua.push commonState
-  Lua.setglobal "PANDOC_STATE"
   installPandocPackageSearcher luaPkgParams
   loadScriptFromDataDir (luaPkgDataDir luaPkgParams) "init.lua"
   putConstructorsInRegistry
 
-registerScriptPath :: FilePath -> Lua ()
-registerScriptPath fp = do
-  Lua.push fp
-  Lua.setglobal "PANDOC_SCRIPT_FILE"
-
 putConstructorsInRegistry :: Lua ()
 putConstructorsInRegistry = do
   Lua.getglobal "pandoc"
diff --git a/src/Text/Pandoc/Writers/Custom.hs b/src/Text/Pandoc/Writers/Custom.hs
index 3ec8781be..7eb982f4b 100644
--- a/src/Text/Pandoc/Writers/Custom.hs
+++ b/src/Text/Pandoc/Writers/Custom.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE FlexibleInstances  #-}
 {-# LANGUAGE NoImplicitPrelude  #-}
 {- Copyright (C) 2012-2018 John MacFarlane <jgm@berkeley.edu>
@@ -36,21 +35,18 @@ import Control.Arrow ((***))
 import Control.Exception
 import Control.Monad (when)
 import Data.Char (toLower)
-import Data.Data (Data)
 import Data.List (intersperse)
 import qualified Data.Map as M
 import Data.Text (Text, pack)
 import Data.Typeable
-import Foreign.Lua (Lua, Peekable, Pushable)
-import Foreign.Lua.Userdata ( ensureUserdataMetatable, pushAnyWithMetatable
-                            , metatableName)
+import Foreign.Lua (Lua, Pushable)
 import Text.Pandoc.Class (PandocIO)
 import Text.Pandoc.Definition
 import Text.Pandoc.Error
-import Text.Pandoc.Lua.Init (LuaException (LuaException), runPandocLua,
-                             registerScriptPath)
+import Text.Pandoc.Lua.Global (Global (..), setGlobals)
+import Text.Pandoc.Lua.Init (LuaException (LuaException), runPandocLua)
 import Text.Pandoc.Lua.StackInstances ()
-import Text.Pandoc.Lua.Util (addField, addFunction, dofileWithTraceback)
+import Text.Pandoc.Lua.Util (addField, dofileWithTraceback)
 import Text.Pandoc.Options
 import Text.Pandoc.Templates
 import qualified Text.Pandoc.UTF8 as UTF8
@@ -109,32 +105,14 @@ data PandocLuaException = PandocLuaException String
 
 instance Exception PandocLuaException
 
--- | Readonly and lazy pandoc objects.
-newtype LazyPandoc = LazyPandoc Pandoc
-  deriving (Data)
-
-instance Pushable LazyPandoc where
-  push lazyDoc = pushAnyWithMetatable pushPandocMetatable lazyDoc
-   where
-    pushPandocMetatable = ensureUserdataMetatable (metatableName lazyDoc) $
-                          addFunction "__index" indexLazyPandoc
-
-instance Peekable LazyPandoc where
-  peek = Lua.peekAny
-
-indexLazyPandoc :: LazyPandoc -> String -> Lua Lua.NumResults
-indexLazyPandoc (LazyPandoc (Pandoc meta blks)) field = 1 <$
-  case field of
-    "blocks" -> Lua.push blks
-    "meta"   -> Lua.push meta
-    _        -> Lua.pushnil
-
 -- | Convert Pandoc to custom markup.
 writeCustom :: FilePath -> WriterOptions -> Pandoc -> PandocIO Text
 writeCustom luaFile opts doc@(Pandoc meta _) = do
+  let globals = [ PANDOC_DOCUMENT doc
+                , PANDOC_SCRIPT_FILE luaFile
+                ]
   res <- runPandocLua $ do
-    Lua.push (LazyPandoc doc) *> Lua.setglobal "PANDOC_DOCUMENT"
-    registerScriptPath luaFile
+    setGlobals globals
     stat <- dofileWithTraceback luaFile
     -- check for error in lua script (later we'll change the return type
     -- to handle this more gracefully):