Add T.P.Lua.Reader, T.P.Lua.Writer.

(Unexported modules, presently.)

These contain the definitions of `readCustom` and `writeCustom`
that were previously in T.P.Readers.Custom and T.P.Writers.Custom.

Motivation is to ensure that all of the Lua-related code is under
the T.P.Lua tree.  This will make it easier to make pandoc-lua
a separate package or put lua support under a flag, if we decide to
do that.

4 files changed, 150 insertions, 115 deletions

diff --git a/src/Text/Pandoc/Lua/Reader.hs b/src/Text/Pandoc/Lua/Reader.hs
new file mode 100644
index 000000000..6303dace3
--- /dev/null
+++ b/src/Text/Pandoc/Lua/Reader.hs
@@ -0,0 +1,84 @@
+{-# LANGUAGE LambdaCase          #-}
+{-# LANGUAGE OverloadedStrings   #-}
+{- |
+   Module      : Text.Pandoc.Lua.Reader
+   Copyright   : Copyright (C) 2021-2022 John MacFarlane
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : John MacFarlane <[email protected]>
+   Stability   : alpha
+   Portability : portable
+
+Supports custom parsers written in Lua which produce a Pandoc AST.
+-}
+module Text.Pandoc.Lua.Reader ( readCustom ) where
+import Control.Exception
+import Control.Monad (when)
+import Control.Monad.IO.Class (MonadIO)
+import Data.Maybe (fromMaybe)
+import HsLua as Lua hiding (Operation (Div))
+import Text.Pandoc.Definition
+import Text.Pandoc.Class (PandocMonad, findFileWithDataFallback, report)
+import Text.Pandoc.Logging
+import Text.Pandoc.Lua.Global (Global (..), setGlobals)
+import Text.Pandoc.Lua.Init (runLua)
+import Text.Pandoc.Lua.PandocLua
+import Text.Pandoc.Lua.Marshal.Pandoc (peekPandoc)
+import Text.Pandoc.Options
+import Text.Pandoc.Sources (ToSources(..), sourcesToText)
+import qualified Data.Text as T
+
+-- | Convert custom markup to Pandoc.
+readCustom :: (PandocMonad m, MonadIO m, ToSources s)
+            => FilePath -> ReaderOptions -> s -> m Pandoc
+readCustom luaFile opts srcs = do
+  let globals = [ PANDOC_SCRIPT_FILE luaFile ]
+  luaFile' <- fromMaybe luaFile <$> findFileWithDataFallback "readers" luaFile
+  res <- runLua $ do
+    setGlobals globals
+    stat <- dofileTrace luaFile'
+    -- check for error in lua script (later we'll change the return type
+    -- to handle this more gracefully):
+    when (stat /= Lua.OK)
+      Lua.throwErrorAsException
+    parseCustom
+  case res of
+    Left msg -> throw msg
+    Right doc -> return doc
+ where
+  parseCustom = do
+    let input = toSources srcs
+    getglobal "Reader"
+    push input
+    push opts
+    pcallTrace 2 1 >>= \case
+      OK -> forcePeek $ peekPandoc top
+      ErrRun -> do
+        -- Caught a runtime error. Check if parsing might work if we
+        -- pass a string instead of a Sources list, then retry.
+        runPeek (peekText top) >>= \case
+          Failure {} ->
+            -- not a string error object. Bail!
+            throwErrorAsException
+          Success errmsg -> do
+            if "string expected, got pandoc Sources" `T.isInfixOf` errmsg
+              then do
+                pop 1
+                _ <- unPandocLua $ do
+                  report $ Deprecated "old Reader function signature" $
+                    T.unlines
+                    [ "Reader functions should accept a sources list; "
+                    , "functions expecting `string` input are deprecated. "
+                    , "Use `tostring` to convert the first argument to a "
+                    , "string."
+                    ]
+                getglobal "Reader"
+                push $ sourcesToText input  -- push sources as string
+                push opts
+                callTrace 2 1
+                forcePeek $ peekPandoc top
+              else
+                -- nothing we can do here
+                throwErrorAsException
+      _ ->  -- not a runtime error, we won't be able to recover from that
+        throwErrorAsException
diff --git a/src/Text/Pandoc/Lua/Writer.hs b/src/Text/Pandoc/Lua/Writer.hs
new file mode 100644
index 000000000..6b4273d88
--- /dev/null
+++ b/src/Text/Pandoc/Lua/Writer.hs
@@ -0,0 +1,64 @@
+{-# LANGUAGE LambdaCase          #-}
+{-# LANGUAGE OverloadedStrings   #-}
+{- |
+   Module      : Text.Pandoc.Lua.Writer
+   Copyright   : Copyright (C) 2012-2022 John MacFarlane
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : John MacFarlane <[email protected]>
+   Stability   : alpha
+   Portability : portable
+
+Conversion of Pandoc documents using a custom Lua writer.
+-}
+module Text.Pandoc.Lua.Writer
+  ( writeCustom
+  ) where
+
+import Control.Exception
+import Control.Monad ((<=<))
+import Data.Maybe (fromMaybe)
+import Data.Text (Text)
+import HsLua
+import Control.Monad.IO.Class (MonadIO)
+import Text.Pandoc.Class (PandocMonad, findFileWithDataFallback)
+import Text.Pandoc.Definition (Pandoc (..))
+import Text.Pandoc.Lua.Global (Global (..), setGlobals)
+import Text.Pandoc.Lua.Init (runLua)
+import Text.Pandoc.Options (WriterOptions)
+import qualified Text.Pandoc.Lua.Writer.Classic as Classic
+
+-- | Convert Pandoc to custom markup.
+writeCustom :: (PandocMonad m, MonadIO m)
+            => FilePath -> WriterOptions -> Pandoc -> m Text
+writeCustom luaFile opts doc = do
+  luaFile' <- fromMaybe luaFile <$> findFileWithDataFallback "writers" luaFile
+  either throw pure <=< runLua $ do
+    setGlobals [ PANDOC_DOCUMENT doc
+               , PANDOC_SCRIPT_FILE luaFile'
+               , PANDOC_WRITER_OPTIONS opts
+               ]
+    dofileTrace luaFile' >>= \case
+      OK -> pure ()
+      _  -> throwErrorAsException
+    -- Most classic writers contain code that throws an error if a global
+    -- is not present. This would break our check for the existence of a
+    -- "Writer" function. We resort to raw access for that reason, but
+    -- could also catch the error instead.
+    let rawgetglobal x = do
+          pushglobaltable
+          pushName x
+          rawget (nth 2) <* remove (nth 2) -- remove global table
+
+    rawgetglobal "Writer" >>= \case
+      TypeNil -> do
+        pop 1  -- remove nil
+        Classic.runCustom opts doc
+      _       -> do
+        -- Writer on top of the stack. Call it with document and writer
+        -- options as arguments.
+        push doc
+        push opts
+        callTrace 2 1
+        forcePeek $ peekText top
+
diff --git a/src/Text/Pandoc/Readers/Custom.hs b/src/Text/Pandoc/Readers/Custom.hs
index 37959574e..9935d1ee6 100644
--- a/src/Text/Pandoc/Readers/Custom.hs
+++ b/src/Text/Pandoc/Readers/Custom.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE LambdaCase          #-}
-{-# LANGUAGE OverloadedStrings   #-}
 {- |
    Module      : Text.Pandoc.Readers.Custom
    Copyright   : Copyright (C) 2021-2022 John MacFarlane
@@ -12,72 +10,4 @@
 Supports custom parsers written in Lua which produce a Pandoc AST.
 -}
 module Text.Pandoc.Readers.Custom ( readCustom ) where
-import Control.Exception
-import Control.Monad (when)
-import Control.Monad.IO.Class (MonadIO)
-import Data.Maybe (fromMaybe)
-import HsLua as Lua hiding (Operation (Div))
-import Text.Pandoc.Definition
-import Text.Pandoc.Class (PandocMonad, findFileWithDataFallback, report)
-import Text.Pandoc.Logging
-import Text.Pandoc.Lua (Global (..), runLua, setGlobals)
-import Text.Pandoc.Lua.PandocLua
-import Text.Pandoc.Lua.Marshal.Pandoc (peekPandoc)
-import Text.Pandoc.Options
-import Text.Pandoc.Sources (ToSources(..), sourcesToText)
-import qualified Data.Text as T
-
--- | Convert custom markup to Pandoc.
-readCustom :: (PandocMonad m, MonadIO m, ToSources s)
-            => FilePath -> ReaderOptions -> s -> m Pandoc
-readCustom luaFile opts srcs = do
-  let globals = [ PANDOC_SCRIPT_FILE luaFile ]
-  luaFile' <- fromMaybe luaFile <$> findFileWithDataFallback "readers" luaFile
-  res <- runLua $ do
-    setGlobals globals
-    stat <- dofileTrace luaFile'
-    -- check for error in lua script (later we'll change the return type
-    -- to handle this more gracefully):
-    when (stat /= Lua.OK)
-      Lua.throwErrorAsException
-    parseCustom
-  case res of
-    Left msg -> throw msg
-    Right doc -> return doc
- where
-  parseCustom = do
-    let input = toSources srcs
-    getglobal "Reader"
-    push input
-    push opts
-    pcallTrace 2 1 >>= \case
-      OK -> forcePeek $ peekPandoc top
-      ErrRun -> do
-        -- Caught a runtime error. Check if parsing might work if we
-        -- pass a string instead of a Sources list, then retry.
-        runPeek (peekText top) >>= \case
-          Failure {} ->
-            -- not a string error object. Bail!
-            throwErrorAsException
-          Success errmsg -> do
-            if "string expected, got pandoc Sources" `T.isInfixOf` errmsg
-              then do
-                pop 1
-                _ <- unPandocLua $ do
-                  report $ Deprecated "old Reader function signature" $
-                    T.unlines
-                    [ "Reader functions should accept a sources list; "
-                    , "functions expecting `string` input are deprecated. "
-                    , "Use `tostring` to convert the first argument to a "
-                    , "string."
-                    ]
-                getglobal "Reader"
-                push $ sourcesToText input  -- push sources as string
-                push opts
-                callTrace 2 1
-                forcePeek $ peekPandoc top
-              else
-                -- nothing we can do here
-                throwErrorAsException
-      _ ->  -- not a runtime error, we won't be able to recover from that
-        throwErrorAsException
+import Text.Pandoc.Lua.Reader ( readCustom )
diff --git a/src/Text/Pandoc/Writers/Custom.hs b/src/Text/Pandoc/Writers/Custom.hs
index b7c99a155..ae0cf0c7e 100644
--- a/src/Text/Pandoc/Writers/Custom.hs
+++ b/src/Text/Pandoc/Writers/Custom.hs
@@ -10,49 +10,6 @@ Conversion of 'Pandoc' documents to custom markup using
 a Lua writer.
 -}
 module Text.Pandoc.Writers.Custom ( writeCustom ) where
-import Control.Exception
-import Control.Monad ((<=<))
-import Data.Maybe (fromMaybe)
-import Data.Text (Text)
-import HsLua
-import Control.Monad.IO.Class (MonadIO)
-import Text.Pandoc.Class (PandocMonad, findFileWithDataFallback)
-import Text.Pandoc.Definition (Pandoc (..))
-import Text.Pandoc.Lua (Global (..), runLua, setGlobals)
-import Text.Pandoc.Options (WriterOptions)
 
-import qualified Text.Pandoc.Lua.Writer.Classic as Classic
+import Text.Pandoc.Lua.Writer ( writeCustom )
 
--- | Convert Pandoc to custom markup.
-writeCustom :: (PandocMonad m, MonadIO m)
-            => FilePath -> WriterOptions -> Pandoc -> m Text
-writeCustom luaFile opts doc = do
-  luaFile' <- fromMaybe luaFile <$> findFileWithDataFallback "writers" luaFile
-  either throw pure <=< runLua $ do
-    setGlobals [ PANDOC_DOCUMENT doc
-               , PANDOC_SCRIPT_FILE luaFile'
-               , PANDOC_WRITER_OPTIONS opts
-               ]
-    dofileTrace luaFile' >>= \case
-      OK -> pure ()
-      _  -> throwErrorAsException
-    -- Most classic writers contain code that throws an error if a global
-    -- is not present. This would break our check for the existence of a
-    -- "Writer" function. We resort to raw access for that reason, but
-    -- could also catch the error instead.
-    let rawgetglobal x = do
-          pushglobaltable
-          pushName x
-          rawget (nth 2) <* remove (nth 2) -- remove global table
-
-    rawgetglobal "Writer" >>= \case
-      TypeNil -> do
-        pop 1  -- remove nil
-        Classic.runCustom opts doc
-      _       -> do
-        -- Writer on top of the stack. Call it with document and writer
-        -- options as arguments.
-        push doc
-        push opts
-        callTrace 2 1
-        forcePeek $ peekText top