Lua module: add readers submodule

Plain text readers are exposed to lua scripts via the `pandoc.reader`
submodule, which is further subdivided by format.  Converting e.g. a
markdown string into a pandoc document is possible from within lua:

    doc = pandoc.reader.markdown.read_doc("Hello, World!")

A `read_block` convenience function is provided for all formats,
although it will still parse the whole string but return only the first
block as the result.

Custom reader options are not supported yet, default options are used
for all parsing operations.

2 files changed, 18 insertions, 0 deletions

diff --git a/test/Tests/Lua.hs b/test/Tests/Lua.hs
index 4f8bd46d8..27a4d8d6f 100644
--- a/test/Tests/Lua.hs
+++ b/test/Tests/Lua.hs
@@ -26,6 +26,12 @@ tests =
       "hello-world-doc.lua"
       (doc . para $ str "Hey!" <> linebreak <> str "What's up?")
       (doc . para $ str "Hello," <> space <> str "World!")
+
+  , testCase "parse raw markdown blocks" $
+    assertFilterConversion "raw markdown block is converted"
+      "markdown-reader.lua"
+      (doc $ rawBlock "markdown" "*charly* **delta**")
+      (doc . para $ emph "charly" <> space <> strong "delta")
   ]
 
 assertFilterConversion :: String -> FilePath -> Pandoc -> Pandoc -> Assertion
diff --git a/test/lua/markdown-reader.lua b/test/lua/markdown-reader.lua
new file mode 100644
index 000000000..6356113ec
--- /dev/null
+++ b/test/lua/markdown-reader.lua
@@ -0,0 +1,12 @@
+return {
+  {
+    RawBlock = function (blk)
+      local format, content = unpack(blk.c)
+      if format == "markdown" then
+        return pandoc.reader.markdown.read_block(content)
+      else
+        return blk
+      end
+    end,
+  }
+}