Lua: fix regression in package searcher

This caused `require 'module'` to fail for third party packages.

Fixes: #6361

1 files changed, 8 insertions, 2 deletions

diff --git a/src/Text/Pandoc/Lua/Packages.hs b/src/Text/Pandoc/Lua/Packages.hs
index 79d42a6d7..4c3b9d79d 100644
--- a/src/Text/Pandoc/Lua/Packages.hs
+++ b/src/Text/Pandoc/Lua/Packages.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {- |
    Module      : Text.Pandoc.Lua.Packages
@@ -14,9 +15,11 @@ module Text.Pandoc.Lua.Packages
   ( installPandocPackageSearcher
   ) where
 
+import Control.Monad.Catch (try)
 import Control.Monad (forM_)
 import Data.ByteString (ByteString)
 import Foreign.Lua (Lua, NumResults)
+import Text.Pandoc.Error (PandocError)
 import Text.Pandoc.Class.PandocMonad (readDataFile)
 import Text.Pandoc.Lua.PandocLua (PandocLua, liftPandocLua)
 
@@ -58,8 +61,11 @@ pandocPackageSearcher pkgName =
     return 1
   searchPureLuaLoader = do
     let filename = pkgName ++ ".lua"
-    script <- readDataFile filename
-    pushWrappedHsFun (loadStringAsPackage pkgName script)
+    try (readDataFile filename) >>= \case
+      Right script -> pushWrappedHsFun (loadStringAsPackage pkgName script)
+      Left (_ :: PandocError) -> liftPandocLua $ do
+        Lua.push ("\n\tno file '" ++ filename ++ "' in pandoc's datadir")
+        return (1 :: NumResults)
 
 loadStringAsPackage :: String -> ByteString -> Lua NumResults
 loadStringAsPackage pkgName script = do