Lua filters

MANUAL.txt

@@ -457,6 +457,31 @@ Reader options
 
      3. `$PATH` (executable only)
 
+`--lua-filter=`*SCRIPT*
+
+:   Transform the document in a similar fashion as JSON filters (see
+    `--filter`), but use pandoc's build-in lua filtering system.  The given
+    lua script is expected to return a list of lua filters which will be
+    applied in order.  Each lua filter must contain element-transforming
+    functions indexed by the name of the AST element on which the filter
+    function should be applied.
+
+    The `pandoc` lua module provides helper functions for element
+    creation.  It is always loaded into the script's lua environment.
+
+    The following is an example lua script for macro-expansion:
+
+        function expand_hello_world(inline)
+          if inline.c == '{{helloworld}}' then
+            return pandoc.Emph{ pandoc.Str "Hello, World" }
+          else
+            return inline
+          end
+        end
+
+        return {{Str = expand_hello_world}}
+
+
 `-M` *KEY*[`=`*VAL*], `--metadata=`*KEY*[`:`*VAL*]
 
 :   Set the metadata field *KEY* to the value *VAL*.  A value specified

data/pandoc.lua

@@ -0,0 +1,144 @@
+--[[
+pandoc.lua
+
+Copyright (c) 2017 Albert Krewinkel
+
+Permission to use, copy, modify, and/or distribute this software for any purpose
+with or without fee is hereby granted, provided that the above copyright notice
+and this permission notice appear in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
+FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS
+OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+THIS SOFTWARE.
+]]
+
+--- The module
+local M = {
+  _version = "0.1.0"
+}
+
+--- Create a new set of attributes (Attr).
+function M.Attributes(id, classes, key_values)
+  return {id, classes, key_values}
+end
+
+local Element = {}
+--- Create a new element subtype
+function Element:make_subtype(o)
+  o = o or {}
+  setmetatable(o, self)
+  self.__index = self
+  return o
+end
+--- Create a new element given its tag and arguments
+function Element:new(tag, ...)
+  local element = { t = tag }
+  local content = {...}
+  -- special case for unary constructors
+  if #content == 1 then
+    element.c = content[1]
+  -- Don't set 'c' field if no further arguments were given. This is important
+  -- for nullary constructors like `Space` and `HorizontalRule`.
+  elseif #content > 0 then
+    element.c = content
+  end
+  setmetatable(element, self)
+  self.__index = self
+  return element
+end
+
+local function Doc(blocks, meta)
+  return {
+    ["blocks"] = blocks,
+    ["meta"] = meta,
+    ["pandoc-api-version"] = {1,17,0,5},
+  }
+end
+
+local Inline = Element:make_subtype{}
+local Block = Element:make_subtype{}
+
+M.block_types = {
+  "BlockQuote",
+  "BulletList",
+  "CodeBlock",
+  "DefinitionList",
+  "Div",
+  "Header",
+  "HorizontalRule",
+  "HorizontalRule",
+  "LineBlock",
+  "Null",
+  "OrderedList",
+  "Para",
+  "Plain",
+  "RawBlock",
+  "Table",
+}
+
+M.inline_types = {
+  "Cite",
+  "Code",
+  "DisplayMath",
+  "DoubleQuoted",
+  "Emph",
+  "Image",
+  "InlineMath",
+  "LineBreak",
+  "Link",
+  "Math",
+  "Note",
+  "Quoted",
+  "RawInline",
+  "SingleQuoted",
+  "SmallCaps",
+  "SoftBreak",
+  "Space",
+  "Span",
+  "Str",
+  "Strikeout",
+  "Strong",
+  "Subscript",
+  "Superscript"
+}
+
+for _, block_type in pairs(M.block_types) do
+  M[block_type] = function(...)
+    return Block:new(block_type, ...)
+  end
+end
+
+for _, inline_type in pairs(M.inline_types) do
+  M[inline_type] = function(...)
+    return Inline:new(inline_type, ...)
+  end
+end
+
+--- Arrays to provide fast lookup of element types
+local set_of_inline_types = {}
+local set_of_block_types = {}
+
+for i = 1, #M.inline_types do
+  set_of_inline_types[M.inline_types[i]] = true
+end
+for i = 1, #M.block_types do
+  set_of_block_types[M.block_types[i]] = true
+end
+
+function M.global_filter()
+  local res = {}
+  for k, v in pairs(_G) do
+    if set_of_inline_types[k] or set_of_block_types[k] or k == "Doc" then
+      res[k] = v
+    end
+  end
+  return res
+end
+
+M["Doc"] = Doc
+
+return M

pandoc.cabal

@@ -104,6 +104,8 @@ Data-Files:
                  data/abbreviations
                  -- sample lua custom writer
                  data/sample.lua
+                 -- pandoc lua module
+                 data/pandoc.lua
                  -- bash completion template
                  data/bash_completion.tpl
                  -- documentation
@@ -232,6 +234,7 @@ Extra-Source-Files:
                  test/odt/odt/*.odt
                  test/odt/markdown/*.md
                  test/odt/native/*.native
+                 test/lua/strmacro.lua
 Source-repository head
   type:          git
   location:      git://github.com/jgm/pandoc.git
@@ -282,6 +285,7 @@ Library
                  pandoc-types >= 1.17 && < 1.18,
                  aeson >= 0.7 && < 1.2,
                  aeson-pretty >= 0.8 && < 0.9,
+                 hslua-aeson >= 0.1.0.2 && < 1,
                  tagsoup >= 0.13.7 && < 0.15,
                  base64-bytestring >= 0.1 && < 1.1,
                  zlib >= 0.5 && < 0.7,
@@ -396,6 +400,7 @@ Library
                    Text.Pandoc.Writers.Muse,
                    Text.Pandoc.Writers.Math,
                    Text.Pandoc.Writers.Shared,
+                   Text.Pandoc.Lua,
                    Text.Pandoc.PDF,
                    Text.Pandoc.UTF8,
                    Text.Pandoc.Templates,
@@ -434,6 +439,7 @@ Library
                    Text.Pandoc.Readers.Org.ParserState,
                    Text.Pandoc.Readers.Org.Parsing,
                    Text.Pandoc.Readers.Org.Shared,
+                   Text.Pandoc.Lua.PandocModule,
                    Text.Pandoc.CSS,
                    Text.Pandoc.UUID,
                    Text.Pandoc.Slides,
@@ -522,6 +528,7 @@ Test-Suite test-pandoc
   Other-Modules:  Tests.Old
                   Tests.Command
                   Tests.Helpers
+                  Tests.Lua
                   Tests.Shared
                   Tests.Readers.LaTeX
                   Tests.Readers.HTML

pandoc.hs

@@ -37,4 +37,3 @@ import Text.Pandoc.App (convertWithOpts, defaultOpts, options, parseOptions)
 
 main :: IO ()
 main = parseOptions options defaultOpts >>= convertWithOpts
-

src/Text/Pandoc/App.hs

@@ -69,6 +69,7 @@ import Text.Pandoc
 import Text.Pandoc.Builder (setMeta)
 import Text.Pandoc.Class (PandocIO, getLog, withMediaBag)
 import Text.Pandoc.Highlighting (highlightingStyles)
+import Text.Pandoc.Lua ( runLuaFilter )
 import Text.Pandoc.MediaBag (MediaBag, extractMediaBag, mediaDirectory)
 import Text.Pandoc.PDF (makePDF)
 import Text.Pandoc.Process (pipeProcess)
@@ -389,6 +390,7 @@ convertWithOpts opts = do
     doc' <- (maybe return (extractMedia media) (optExtractMedia opts) >=>
               return . flip (foldr addMetadata) (optMetadata opts) >=>
               applyTransforms transforms >=>
+              applyLuaFilters datadir (optLuaFilters opts) [format] >=>
               applyFilters datadir filters' [format]) doc
 
     case writer of
@@ -514,6 +516,7 @@ data Opt = Opt
     , optWrapText              :: WrapOption  -- ^ Options for wrapping text
     , optColumns               :: Int     -- ^ Line length in characters
     , optFilters               :: [FilePath] -- ^ Filters to apply
+    , optLuaFilters            :: [FilePath] -- ^ Lua filters to apply
     , optEmailObfuscation      :: ObfuscationMethod
     , optIdentifierPrefix      :: String
     , optIndentedCodeClasses   :: [String] -- ^ Default classes for indented code blocks
@@ -580,6 +583,7 @@ defaultOpts = Opt
     , optWrapText              = WrapAuto
     , optColumns               = 72
     , optFilters               = []
+    , optLuaFilters            = []
     , optEmailObfuscation      = NoObfuscation
     , optIdentifierPrefix      = ""
     , optIndentedCodeClasses   = []
@@ -725,6 +729,12 @@ expandFilterPath mbDatadir fp = liftIO $ do
                     else return fp
                _ -> return fp
 
+applyLuaFilters :: MonadIO m
+                => Maybe FilePath -> [FilePath] -> [String] -> Pandoc -> m Pandoc
+applyLuaFilters mbDatadir filters args d = do
+  expandedFilters <- mapM (expandFilterPath mbDatadir) filters
+  foldrM ($) d $ map (flip runLuaFilter args) expandedFilters
+
 applyFilters :: MonadIO m
              => Maybe FilePath -> [FilePath] -> [String] -> Pandoc -> m Pandoc
 applyFilters mbDatadir filters args d = do
@@ -814,6 +824,12 @@ options =
                   "PROGRAM")
                  "" -- "External JSON filter"
 
+    , Option "" ["lua-filter"]
+                 (ReqArg
+                  (\arg opt -> return opt { optLuaFilters = arg : optLuaFilters opt })
+                  "SCRIPTPATH")
+                 "" -- "Lua filter"
+
     , Option "p" ["preserve-tabs"]
                  (NoArg
                   (\opt -> return opt { optPreserveTabs = True }))