From 0105a3c2930675971ea83da3b987c6b62f97ce26 Mon Sep 17 00:00:00 2001
From: Albert Krewinkel <albert+github@zeitkraut.de>
Date: Wed, 29 Nov 2017 01:20:01 +0100
Subject: Add basic lua List module (#4099)

The List module is automatically loaded, but not assigned to a global
variable. It can be included in filters by calling `List = require
'List'`.

Lists of blocks, lists of inlines, and lists of classes are now given
`List` as a metatable, making working with them more convenient. E.g.,
it is now possible to concatenate lists of inlines using Lua's
concatenation operator `..` (requires at least one of the operants to
have `List` as a metatable):

    function Emph (emph)
      local s = {pandoc.Space(), pandoc.Str 'emphasized'}
      return pandoc.Span(emph.content .. s)
    end

Closes: #4081
---
 src/Text/Pandoc/Lua/PandocModule.hs | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

(limited to 'src/Text/Pandoc/Lua')

diff --git a/src/Text/Pandoc/Lua/PandocModule.hs b/src/Text/Pandoc/Lua/PandocModule.hs
index ac7839d0f..ba3193211 100644
--- a/src/Text/Pandoc/Lua/PandocModule.hs
+++ b/src/Text/Pandoc/Lua/PandocModule.hs
@@ -59,10 +59,12 @@ import qualified Foreign.Lua as Lua
 import qualified Text.Pandoc.MediaBag as MB
 import Text.Pandoc.Lua.Filter (walkInlines, walkBlocks, LuaFilter)
 
--- | Push the "pandoc" on the lua stack.
+-- | Push the "pandoc" on the lua stack. Requires the `list` module to be
+-- loaded.
 pushPandocModule :: Maybe FilePath -> Lua ()
 pushPandocModule datadir = do
-  script <- liftIO (pandocModuleScript datadir)
+  loadListModule datadir
+  script <- liftIO (moduleScript datadir "pandoc.lua")
   status <- Lua.loadstring script
   unless (status /= Lua.OK) $ Lua.call 0 1
   addFunction "_pipe" pipeFn
@@ -72,9 +74,25 @@ pushPandocModule datadir = do
   addFunction "walk_inline" walkInline
 
 -- | Get the string representation of the pandoc module
-pandocModuleScript :: Maybe FilePath -> IO String
-pandocModuleScript datadir = unpack <$>
-  runIOorExplode (setUserDataDir datadir >> readDataFile "pandoc.lua")
+moduleScript :: Maybe FilePath -> FilePath -> IO String
+moduleScript datadir moduleFile = unpack <$>
+  runIOorExplode (setUserDataDir datadir >> readDataFile moduleFile)
+
+-- Loads pandoc's list module without assigning it to a variable.
+pushListModule :: Maybe FilePath -> Lua ()
+pushListModule datadir = do
+  script <- liftIO (moduleScript datadir "List.lua")
+  status <- Lua.loadstring script
+  if status == Lua.OK
+    then Lua.call 0 1
+    else Lua.throwTopMessageAsError' ("Error while loading module `list`\n" ++)
+
+loadListModule :: Maybe FilePath -> Lua ()
+loadListModule datadir = do
+  Lua.getglobal' "package.loaded"
+  pushListModule datadir
+  Lua.setfield (-2) "List"
+  Lua.pop 1
 
 walkElement :: (ToLuaStack a, Walkable [Inline] a, Walkable [Block] a)
             => a -> LuaFilter -> Lua NumResults
-- 
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