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|
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedStrings #-}
{- |
Module : Text.Pandoc.Lua
Copyright : Copyright © 2017-2021 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
( runLua
) where
import Control.Monad (forM, forM_, when)
import Control.Monad.Catch (throwM, try)
import Control.Monad.Trans (MonadIO (..))
import Data.Data (Data, dataTypeConstrs, dataTypeOf, showConstr)
import Data.Maybe (catMaybes)
import HsLua as Lua hiding (status, try)
import GHC.IO.Encoding (getForeignEncoding, setForeignEncoding, utf8)
import Text.Pandoc.Class.PandocMonad (PandocMonad, readDataFile)
import Text.Pandoc.Error (PandocError (PandocLuaError))
import Text.Pandoc.Lua.Packages (installPandocPackageSearcher)
import Text.Pandoc.Lua.PandocLua (PandocLua, liftPandocLua, runPandocLua)
import qualified Data.Text as T
import qualified Lua.LPeg as LPeg
import qualified Text.Pandoc.Definition as Pandoc
import qualified Text.Pandoc.Lua.Module.Pandoc as ModulePandoc
-- | Run the lua interpreter, using pandoc's default way of environment
-- initialization.
runLua :: (PandocMonad m, MonadIO m)
=> LuaE PandocError a -> m (Either PandocError a)
runLua luaOp = do
enc <- liftIO $ getForeignEncoding <* setForeignEncoding utf8
res <- runPandocLua . try $ do
initLuaState
liftPandocLua luaOp
liftIO $ setForeignEncoding enc
return res
-- | Initialize the lua state with all required values
initLuaState :: PandocLua ()
initLuaState = do
liftPandocLua Lua.openlibs
installPandocPackageSearcher
initPandocModule
installLpegSearcher
setGlobalModules
loadInitScript "init.lua"
where
initPandocModule :: PandocLua ()
initPandocModule = do
-- Push module table
ModulePandoc.pushModule
-- register as loaded module
liftPandocLua $ do
Lua.getfield Lua.registryindex Lua.loaded
Lua.pushvalue (Lua.nth 2)
Lua.setfield (Lua.nth 2) "pandoc"
Lua.pop 1
-- copy constructors into registry
putConstructorsInRegistry
-- assign module to global variable
liftPandocLua $ Lua.setglobal "pandoc"
loadInitScript :: FilePath -> PandocLua ()
loadInitScript scriptFile = do
script <- readDataFile scriptFile
status <- liftPandocLua $ Lua.dostring script
when (status /= Lua.OK) . liftPandocLua $ do
err <- popException
let prefix = "Couldn't load '" <> T.pack scriptFile <> "':\n"
throwM . PandocLuaError . (prefix <>) $ case err of
PandocLuaError msg -> msg
_ -> T.pack $ show err
setGlobalModules :: PandocLua ()
setGlobalModules = liftPandocLua $ do
let globalModules =
[ ("lpeg", LPeg.luaopen_lpeg_ptr) -- must be loaded first
, ("re", LPeg.luaopen_re_ptr) -- re depends on lpeg
]
loadedBuiltInModules <- fmap catMaybes . forM globalModules $
\(pkgname, luaopen) -> do
Lua.pushcfunction luaopen
usedBuiltIn <- Lua.pcall 0 1 Nothing >>= \case
OK -> do -- all good, loading succeeded
-- register as loaded module so later modules can rely on this
Lua.getfield Lua.registryindex Lua.loaded
Lua.pushvalue (Lua.nth 2)
Lua.setfield (Lua.nth 2) pkgname
Lua.pop 1 -- pop _LOADED
return True
_ -> do -- built-in library failed, load system lib
Lua.pop 1 -- ignore error message
-- Try loading via the normal package loading mechanism.
Lua.getglobal "require"
Lua.pushName pkgname
Lua.call 1 1 -- Throws an exception if loading failed again!
return False
-- Module on top of stack. Register as global
Lua.setglobal pkgname
return $ if usedBuiltIn then Just pkgname else Nothing
-- Remove module entry from _LOADED table in registry if we used a
-- built-in library. This ensures that later calls to @require@ will
-- prefer the shared library, if any.
forM_ loadedBuiltInModules $ \pkgname -> do
Lua.getfield Lua.registryindex Lua.loaded
Lua.pushnil
Lua.setfield (Lua.nth 2) pkgname
Lua.pop 1 -- registry
installLpegSearcher :: PandocLua ()
installLpegSearcher = liftPandocLua $ do
Lua.getglobal' "package.searchers"
Lua.pushHaskellFunction $ Lua.state >>= liftIO . LPeg.lpeg_searcher
Lua.rawseti (Lua.nth 2) . (+1) . fromIntegral =<< Lua.rawlen (Lua.nth 2)
Lua.pop 1 -- remove 'package.searchers' from stack
-- | AST elements are marshaled via normal constructor functions in the
-- @pandoc@ module. However, accessing Lua globals from Haskell is
-- expensive (due to error handling). Accessing the Lua registry is much
-- cheaper, which is why the constructor functions are copied into the
-- Lua registry and called from there.
--
-- This function expects the @pandoc@ module to be at the top of the
-- stack.
putConstructorsInRegistry :: PandocLua ()
putConstructorsInRegistry = liftPandocLua $ do
constrsToReg $ Pandoc.Meta mempty
constrsToReg $ Pandoc.MetaList mempty
putInReg "List" -- pandoc.List
putInReg "SimpleTable" -- helper for backward-compatible table handling
where
constrsToReg :: Data a => a -> LuaE PandocError ()
constrsToReg = mapM_ (putInReg . showConstr) . dataTypeConstrs . dataTypeOf
putInReg :: String -> LuaE PandocError ()
putInReg name = do
Lua.push ("pandoc." ++ name) -- name in registry
Lua.push name -- in pandoc module
Lua.rawget (Lua.nth 3)
Lua.rawset Lua.registryindex
|
