Added parameter for user data directory to runLuaFilter.

in Text.Pandoc.Lua.  Also to pushPandocModule.

This change allows users to override pandoc.lua with a file
in their local data directory, adding custom functions, etc.

@tarleb, if you think this is a bad idea, you can revert this.
But in general our data files are all overridable.

src/Text/Pandoc/App.hs

@@ -795,7 +795,7 @@ applyLuaFilters :: MonadIO m
 applyLuaFilters mbDatadir filters args d = do
   expandedFilters <- mapM (expandFilterPath mbDatadir) filters
   let go f d' = liftIO $ do
-        res <- E.try (runLuaFilter f args d')
+        res <- E.try (runLuaFilter mbDatadir f args d')
         case res of
              Right x -> return x
              Left (LuaException s) -> E.throw (PandocFilterError f s)

src/Text/Pandoc/Lua.hs

@@ -56,12 +56,12 @@ newtype LuaException = LuaException String
 instance Exception LuaException
 
 runLuaFilter :: (MonadIO m)
-             => FilePath -> [String] -> Pandoc -> m Pandoc
-runLuaFilter filterPath args pd = liftIO $ do
+             => Maybe FilePath -> FilePath -> [String] -> Pandoc -> m Pandoc
+runLuaFilter datadir filterPath args pd = liftIO $ do
   lua <- Lua.newstate
   Lua.openlibs lua
   -- store module in global "pandoc"
-  pushPandocModule lua
+  pushPandocModule datadir lua
   Lua.setglobal lua "pandoc"
   top <- Lua.gettop lua
   status <- Lua.loadfile lua filterPath

src/Text/Pandoc/Lua/PandocModule.hs

@@ -41,9 +41,9 @@ import Text.Pandoc.Readers (Reader (..), getReader)
 import Text.Pandoc.Shared (readDataFile)
 
 -- | Push the "pandoc" on the lua stack.
-pushPandocModule :: LuaState -> IO ()
-pushPandocModule lua = do
-  script <- pandocModuleScript
+pushPandocModule :: Maybe FilePath -> LuaState -> IO ()
+pushPandocModule datadir lua = do
+  script <- pandocModuleScript datadir
   status <- loadstring lua script "pandoc.lua"
   unless (status /= 0) $ call lua 0 1
   push lua "__read"
@@ -51,8 +51,8 @@ pushPandocModule lua = do
   rawset lua (-3)
 
 -- | Get the string representation of the pandoc module
-pandocModuleScript :: IO String
-pandocModuleScript = unpack <$> readDataFile Nothing "pandoc.lua"
+pandocModuleScript :: Maybe FilePath -> IO String
+pandocModuleScript datadir = unpack <$> readDataFile datadir "pandoc.lua"
 
 read_doc :: String -> String -> IO (Either String Pandoc)
 read_doc formatSpec content = do

test/Tests/Lua.hs

@@ -68,7 +68,7 @@ tests = map (localOption (QuickCheckTests 20))
 
 assertFilterConversion :: String -> FilePath -> Pandoc -> Pandoc -> Assertion
 assertFilterConversion msg filterPath docIn docExpected = do
-  docRes <- runLuaFilter ("lua" </> filterPath) [] docIn
+  docRes <- runLuaFilter Nothing ("lua" </> filterPath) [] docIn
   assertEqual msg docExpected docRes
 
 roundtripEqual :: (Eq a, Lua.StackValue a) => a -> IO Bool
@@ -78,7 +78,7 @@ roundtripEqual x = (x ==) <$> roundtripped
   roundtripped = do
     lua <- Lua.newstate
     Lua.openlibs lua
-    pushPandocModule lua
+    pushPandocModule Nothing lua
     Lua.setglobal lua "pandoc"
     oldSize <- Lua.gettop lua
     Lua.push lua x