From efecff1f2f035ee3a0825e969d048d6c5ffacd26 Mon Sep 17 00:00:00 2001
From: Albert Krewinkel <albert@zeitkraut.de>
Date: Tue, 27 Sep 2022 13:09:55 +0200
Subject: pandoc-cli: support `-E` flag in pandoc-lua

---
 src/Text/Pandoc/Lua.hs      |  3 ++-
 src/Text/Pandoc/Lua/Init.hs | 14 ++++++++++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/Text/Pandoc/Lua.hs b/src/Text/Pandoc/Lua.hs
index 28e807ae9..085526cb7 100644
--- a/src/Text/Pandoc/Lua.hs
+++ b/src/Text/Pandoc/Lua.hs
@@ -20,11 +20,12 @@ module Text.Pandoc.Lua
   , Global(..)
   , setGlobals
   , runLua
+  , runLuaNoEnv
   ) where
 
 import Text.Pandoc.Lua.Filter (applyFilter)
 import Text.Pandoc.Lua.Global (Global (..), setGlobals)
-import Text.Pandoc.Lua.Init (runLua)
+import Text.Pandoc.Lua.Init (runLua, runLuaNoEnv)
 import Text.Pandoc.Lua.Reader (readCustom)
 import Text.Pandoc.Lua.Writer (writeCustom)
 import Text.Pandoc.Lua.Orphans ()
diff --git a/src/Text/Pandoc/Lua/Init.hs b/src/Text/Pandoc/Lua/Init.hs
index 966f0a581..04f007e0e 100644
--- a/src/Text/Pandoc/Lua/Init.hs
+++ b/src/Text/Pandoc/Lua/Init.hs
@@ -12,6 +12,7 @@ Functions to initialize the Lua interpreter.
 -}
 module Text.Pandoc.Lua.Init
   ( runLua
+  , runLuaNoEnv
   ) where
 
 import Control.Monad (forM, forM_, when)
@@ -46,6 +47,19 @@ runLua action =
     initLuaState
     liftPandocLua action
 
+-- | Like 'runLua', but ignores all environment variables like @LUA_PATH@.
+runLuaNoEnv :: (PandocMonad m, MonadIO m)
+            => LuaE PandocError a -> m (Either PandocError a)
+runLuaNoEnv action =
+  runPandocLua . try $ do
+    liftPandocLua $ do
+      -- This is undocumented, but works -- the code is adapted from the
+      -- `lua.c` sources for the default interpreter.
+      Lua.pushboolean True
+      Lua.setfield Lua.registryindex "LUA_NOENV"
+    initLuaState
+    liftPandocLua action
+
 -- | Modules that are loaded at startup and assigned to fields in the
 -- pandoc module.
 --
-- 
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