Merge pull request #3952 from tarleb/lua-pipe-wrapper

Lua pipe wrapper

data/pandoc.lua

@@ -782,7 +782,7 @@ M.UpperAlpha = "UpperAlpha"
 -- assert(block.content[1].t == "Emph")
 function M.read(markup, format)
   format = format or "markdown"
-  local pd = pandoc.__read(format, markup)
+  local pd = pandoc._read(format, markup)
   if type(pd) == "string" then
     error(pd)
   else
@@ -790,6 +790,29 @@ function M.read(markup, format)
   end
 end
 
+--- Runs command with arguments, passing it some input, and returns the output.
+-- @treturn string Output of command.
+-- @usage
+-- local ec, output = pandoc.pipe("sed", {"-e","s/a/b/"}, "abc")
+function M.pipe (command, args, input)
+  local ec, output = pandoc._pipe(command, args, input)
+  if ec ~= 0 then
+    err = setmetatable(
+      { command = command, error_code = ec, output = output},
+      { __tostring = function(e)
+          return "Error running " .. e.command
+            .. " (error code " .. e.error_code .. "): "
+            .. e.output
+        end
+      }
+    )
+    -- TODO: drop the wrapping call to `tostring` as soon as hslua supports
+    -- non-string error objects.
+    error(tostring(err))
+  end
+  return output
+end
+
 --- 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.

src/Text/Pandoc/Lua/PandocModule.hs

@@ -41,6 +41,7 @@ import Data.IORef
 import Data.Maybe (fromMaybe)
 import Data.Text (pack)
 import Foreign.Lua (Lua, FromLuaStack, ToLuaStack, NumResults, liftIO)
+import Foreign.Lua.FunctionCalling (ToHaskellFunction)
 import Text.Pandoc.Class (readDataFile, runIO,
                           runIOorExplode, setUserDataDir, CommonState(..),
                           putCommonState, fetchItem, setMediaBag)
@@ -62,15 +63,9 @@ pushPandocModule datadir = do
   script <- liftIO (pandocModuleScript datadir)
   status <- Lua.loadstring script
   unless (status /= Lua.OK) $ Lua.call 0 1
-  Lua.push "__read"
-  Lua.pushHaskellFunction readDoc
-  Lua.rawset (-3)
-  Lua.push "sha1"
-  Lua.pushHaskellFunction sha1HashFn
-  Lua.rawset (-3)
-  Lua.push "pipe"
-  Lua.pushHaskellFunction pipeFn
-  Lua.rawset (-3)
+  addFunction "_pipe" pipeFn
+  addFunction "_read" readDoc
+  addFunction "sha1" sha1HashFn
 
 -- | Get the string representation of the pandoc module
 pandocModuleScript :: Maybe FilePath -> IO String
@@ -102,11 +97,12 @@ pushMediaBagModule commonState mediaBagRef = do
   addFunction "list" (mediaDirectoryFn mediaBagRef)
   addFunction "fetch" (fetch commonState mediaBagRef)
   return ()
- where
-  addFunction name fn = do
-    Lua.push name
-    Lua.pushHaskellFunction fn
-    Lua.rawset (-3)
+
+addFunction :: ToHaskellFunction a => String -> a -> Lua ()
+addFunction name fn = do
+  Lua.push name
+  Lua.pushHaskellFunction fn
+  Lua.rawset (-3)
 
 sha1HashFn :: BL.ByteString
            -> Lua NumResults