"""

A Python-Markdown preprocessor extension to ignore html comments opened by

three dashes (<!---comment-->) and any whitespace prior to them. I believe

pandoc has similar functionality.

Note: This extension does not work with the markdownfromFile function or

the convertFile method. They raise a UnicodeDecodeError.

Note: If using multiple extensions, mkdcomments probably should be last in

the list. Markdown extensions are loaded into the OrderedDict from which they

are executed in the order of the extension list. If a different extension is

loaded after mkdcomments, it may insert itself before mkdcomments in the

OrderedDict. Undesirable results may ensue. If, for instance, the 'meta'

extension is executed before mkdcomments, any comments in the meta-data will be

included in meta's dictionary.

"""

import re

from markdown.preprocessors import Preprocessor

from markdown.extensions import Extension

class CommentsExtension(Extension):

def extendMarkdown(self, md, md_globals):

md.registerExtension(self)

md.preprocessors.add("comments", CommentsProcessor(md), "_begin")

class CommentsProcessor(Preprocessor):

def run(self, lines):

new_lines = []

multi = False

for line in lines:

if not multi:

multi = self._uncommenter(line)[1]

new_lines.append(self._uncommenter(line)[0])

else:

multi = self._unmultiliner(line)[1]

new_lines.append(self._unmultiliner(line)[0])

return new_lines

def _uncommenter(self, line):

if re.match(r'.*<!---.*-->', line): # inline(could start multiline)

return self._uncommenter(re.sub(r'\s*<!---.*?-->', '', line))

elif re.match(r'.*<!---', line): # start multiline

return [re.sub(r'\s*<!---.*', '', line), True]

else: # no comment

return [line, False]

def _unmultiliner(self, line):

if re.match(r'.*-->', line): # end multiline (could start comment)

return self._uncommenter(re.sub(r'.*?-->', '', line, count=1))

else:

return ['', True] # continue multiline