[API Change] Extract Lua code into new package pandoc-lua-engine

The flag 'lua53` must now be used with that package if pandoc is to be
compiled against Lua 5.3.

1 files changed, 40 insertions, 0 deletions

diff --git a/pandoc-lua-engine/src/Text/Pandoc/Lua/ErrorConversion.hs b/pandoc-lua-engine/src/Text/Pandoc/Lua/ErrorConversion.hs
new file mode 100644
index 000000000..3968eba84
--- /dev/null
+++ b/pandoc-lua-engine/src/Text/Pandoc/Lua/ErrorConversion.hs
@@ -0,0 +1,40 @@
+{-# OPTIONS_GHC -fno-warn-orphans #-}
+{- |
+   Module      : Text.Pandoc.Lua.ErrorConversion
+   Copyright   : © 2020-2022 Albert Krewinkel
+   License     : GNU GPL, version 2 or above
+
+   Maintainer  : Albert Krewinkel <tarleb+pandoc@moltkeplatz.de>
+   Stability   : alpha
+
+Define how Lua errors are converted into @'PandocError'@ Haskell
+exceptions, and /vice versa/.
+-}
+module Text.Pandoc.Lua.ErrorConversion
+  ( addContextToException
+  ) where
+
+import HsLua (LuaError, LuaE, resultToEither, runPeek, top)
+import Text.Pandoc.Error (PandocError (PandocLuaError))
+import Text.Pandoc.Lua.Marshal.PandocError (pushPandocError, peekPandocError)
+
+import qualified Data.Text as T
+import qualified HsLua as Lua
+
+addContextToException :: ()
+addContextToException = undefined
+
+-- | Retrieve a @'PandocError'@ from the Lua stack.
+popPandocError :: LuaE PandocError PandocError
+popPandocError = do
+  errResult <- runPeek $ peekPandocError top
+  case resultToEither errResult of
+    Right x -> return x
+    Left err -> return $ PandocLuaError (T.pack err)
+
+-- Ensure conversions between Lua errors and 'PandocError' exceptions
+-- are possible.
+instance LuaError PandocError where
+  popException = popPandocError
+  pushException = pushPandocError
+  luaException = PandocLuaError . T.pack