add a lua version

filter.hs

@@ -6,15 +6,14 @@ import qualified Data.Text as T
 
 file2Block :: FilePath -> IO [Block]
 file2Block f = do
-  contents <- TIO.readFile f
-  return [Plain [Str contents]]
+    contents <- TIO.readFile f
+    return [Plain [Str contents]]
 
 doInclude :: Block -> IO Block
 doInclude cb@(Div (id, classes, namevals) contents) =
-  case lookup (T.pack "include") namevals of
-       Just f     -> Div (id, classes, namevals) <$>
-                      file2Block (T.unpack f)
-       Nothing    -> return cb
+    case lookup (T.pack "include") namevals of
+    Just f  -> Div (id, classes, namevals) <$> file2Block (T.unpack f)
+    Nothing -> return cb
 doInclude x = return x
 
 main :: IO ()

filter.lua

@@ -0,0 +1,20 @@
+function File2Block(filename)
+    local fh = io.open(filename, "r")
+    if not fh then
+        io.stderr:write("Cannot open file: " .. filename .. "\n")
+        return { pandoc.Plain { pandoc.Str("[Error: cannot read file " .. filename .. "]") } }
+    end
+    local contents = fh:read("*a")
+    fh:close()
+    return { pandoc.Plain { pandoc.Str(contents) } }
+end
+
+function Div(e)
+    local include = e.attributes["include"]
+    if include then
+        local blocks = File2Block(include)
+        -- Replace the Div contents
+        return pandoc.Div(blocks, e.attr)
+    end
+    return nil -- no change
+end

makefile

@@ -4,8 +4,11 @@
 nofilter:
 	pandoc -fmarkdown -thtml input.md > output.html
 
-filter:
+hs:
 	pandoc -fmarkdown -thtml input.md --filter ./filter.hs > output.html
 
+lua:
+	pandoc -fmarkdown -thtml input.md --lua-filter ./filter.lua > output.html
+
 showAST:
 	pandoc -fmarkdown -tnative input.md

output.html

@@ -1,5 +1,6 @@
 <p>Here’s the pandoc README:</p>
-<div class="sourceCode" id="cb1" data-include="filter.hs"><pre
+<div class="sourceCode" id="cb1" data-include="filter.hs"
+style="background-color: red"><pre
 class="sourceCode haskell"><code class="sourceCode haskell"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="dt">Foo</span><span class="ot">::</span> <span class="dt">Div</span> <span class="ot">-&gt;</span> <span class="dt">Div</span></span></code></pre></div>
 <div data-include="filter.hs">
 #!/usr/bin/env runhaskell
@@ -10,15 +11,15 @@ import qualified Data.Text as T
 
 file2Block :: FilePath -&gt; IO [Block]
 file2Block f = do
-  contents &lt;- TIO.readFile f
-  return [Plain [Str contents]]
+    contents &lt;- TIO.readFile f
+    return [Plain [Str contents]]
 
 doInclude :: Block -&gt; IO Block
 doInclude cb@(Div (id, classes, namevals) contents) =
-  case lookup (T.pack "include") namevals of
-       Just f     -&gt; Div (id, classes, namevals) &lt;$&gt;
-                      file2Block (T.unpack f)
-       Nothing    -&gt; return cb
+    case lookup (T.pack "include") namevals of
+    Just f  -&gt; Div (id, classes, namevals) &lt;$&gt; file2Block
+(T.unpack f)
+    Nothing -&gt; return cb
 doInclude x = return x
 
 main :: IO ()