data/pandoc.lua: drop function pandoc.global_filter

The function `global_filter` was used internally to get the implicitly
defined global filter. It was of little value to end-users, but caused
unnecessary code duplication in pandoc. The function has hence been
dropped. Internally, the global filter is now received by interpreting
the global table as lua filter.

This is a Lua API change.

data/pandoc.lua

@@ -23,7 +23,7 @@ THIS SOFTWARE.
 -- @copyright © 2017 Albert Krewinkel
 -- @license MIT
 local M = {
-  _VERSION = "0.3.0"
+  _VERSION = "0.4.0"
 }
 
 local List = require 'pandoc.List'
@@ -868,41 +868,6 @@ M.LowerAlpha = "LowerAlpha"
 -- @see OrderedList
 M.UpperAlpha = "UpperAlpha"
 
-
-------------------------------------------------------------------------
--- Helper Functions
--- @section helpers
-
---- Use functions defined in the global namespace to create a pandoc filter.
--- All globally defined functions which have names of pandoc elements are
--- collected into a new table.
--- @return A list of filter functions
--- @usage
--- -- within a file defining a pandoc filter:
--- text = require 'text'
--- function Str(elem)
---   return pandoc.Str(text.upper(elem.text))
--- end
---
--- return {pandoc.global_filter()}
--- -- the above is equivalent to
--- -- return {{Str = Str}}
-function M.global_filter()
-  local res = {}
-  function is_filter_function(k)
-    return M.Inline.constructor[k] or
-      M.Block.constructor[k] or
-      k == "Meta" or k == "Doc" or k == "Pandoc" or
-      k == "Block" or k == "Inline"
-  end
-  for k, v in pairs(_G) do
-    if is_filter_function(k) then
-      res[k] = v
-    end
-  end
-  return res
-end
-
 ------------------------------------------------------------------------
 -- Functions which have moved to different modules
 local utils = require 'pandoc.utils'

doc/lua-filters.md

@@ -1325,25 +1325,6 @@ Lua functions for pandoc scripts.
 
 ## Helper Functions
 
-[`global_filter ()`]{#global_filter}
-
-:   Use functions defined in the global namespace to create a
-    pandoc filter.
-
-    Returns: A list of filter functions
-
-    Usage:
-
-        -- within a file defining a pandoc filter:
-        text = require 'text'
-        function Str(elem)
-          return pandoc.Str(text.upper(elem.text))
-        end
-
-        return {pandoc.global_filter()}
-        -- the above is equivalent to
-        -- return {{Str = Str}}
-
 [`pipe (command, args, input)`]{#pipe}
 
 :   Runs command with arguments, passing it some input, and

src/Text/Pandoc/Lua.hs

@@ -32,7 +32,7 @@ module Text.Pandoc.Lua
   , pushPandocModule
   ) where
 
-import Control.Monad (when, (>=>))
+import Control.Monad ((>=>))
 import Foreign.Lua (FromLuaStack (peek), Lua, LuaException (..),
                     Status (OK), ToLuaStack (push))
 import Text.Pandoc.Class (PandocIO)
@@ -40,6 +40,7 @@ import Text.Pandoc.Definition (Pandoc)
 import Text.Pandoc.Lua.Filter (LuaFilter, walkMWithLuaFilter)
 import Text.Pandoc.Lua.Init (runPandocLua)
 import Text.Pandoc.Lua.Module.Pandoc (pushModule) -- TODO: remove
+import Text.Pandoc.Lua.Util (popValue)
 import qualified Foreign.Lua as Lua
 
 -- | Run the Lua filter in @filterPath@ for a transformation to target
@@ -63,22 +64,17 @@ runLuaFilter' filterPath format pd = do
       Lua.throwLuaError luaErrMsg
     else do
       newtop <- Lua.gettop
-      -- Use the implicitly defined global filter if nothing was returned
-      when (newtop - top < 1) pushGlobalFilter
-      luaFilters <- peek (-1)
+      -- Use the returned filters, or the implicitly defined global filter if
+      -- nothing was returned.
+      luaFilters <- if (newtop - top >= 1)
+                    then peek (-1)
+                    else Lua.getglobal "_G" *> fmap (:[]) popValue
       runAll luaFilters pd
  where
   registerFormat = do
     push format
     Lua.setglobal "FORMAT"
 
-pushGlobalFilter :: Lua ()
-pushGlobalFilter = do
-  Lua.newtable
-  Lua.getglobal' "pandoc.global_filter"
-  Lua.call 0 1
-  Lua.rawseti (-2) 1
-
 runAll :: [LuaFilter] -> Pandoc -> Lua Pandoc
 runAll = foldr ((>=>) . walkMWithLuaFilter) return
 

src/Text/Pandoc/Lua/Filter.hs

@@ -164,5 +164,3 @@ singleElement x = do
         Lua.throwLuaError $
           "Error while trying to get a filter's return " ++
           "value from lua stack.\n" ++ err
-
-

src/Text/Pandoc/Lua/Util.hs

@@ -37,6 +37,7 @@ module Text.Pandoc.Lua.Util
   , setRawInt
   , addRawInt
   , raiseError
+  , popValue
   , OrNil (..)
   , PushViaCall
   , pushViaCall