Integrate pass-through of mathematical expressions with markdown rendering

IPython/nbconvert/filters/markdown.py

@@ -1,153 +1,203 b''
 """Markdown filters
 This file contains a collection of utility filters for dealing with 
 markdown within Jinja templates.
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2013, the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 from __future__ import print_function
 
 # Stdlib imports
 import os
 import subprocess
 from io import TextIOWrapper, BytesIO
+import re
 
 import mistune
 from pygments import highlight
 from pygments.lexers import get_lexer_by_name
 from pygments.formatters import HtmlFormatter
 
 # IPython imports
 from IPython.nbconvert.utils.pandoc import pandoc
 from IPython.nbconvert.utils.exceptions import ConversionException
 from IPython.utils.process import get_output_error_code
 from IPython.utils.py3compat import cast_bytes
 from IPython.utils.version import check_version
 
 #-----------------------------------------------------------------------------
 # Functions
 #-----------------------------------------------------------------------------
 marked = os.path.join(os.path.dirname(__file__), "marked.js")
 _node = None
 
 __all__ = [
     'markdown2html',
     'markdown2html_pandoc',
     'markdown2html_marked',
     'markdown2html_mistune',
     'markdown2latex',
     'markdown2rst',
 ]
 
 class NodeJSMissing(ConversionException):
     """Exception raised when node.js is missing."""
     pass
 
 def markdown2latex(source):
     """Convert a markdown string to LaTeX via pandoc.
 
     This function will raise an error if pandoc is not installed.
     Any error messages generated by pandoc are printed to stderr.
 
     Parameters
     ----------
     source : string
       Input string, assumed to be valid markdown.
 
     Returns
     -------
     out : string
       Output as returned by pandoc.
     """
     return pandoc(source, 'markdown', 'latex')
 
+class MathBlockGrammar(mistune.BlockGrammar):
+    block_math = re.compile("^\$\$(.*?)\$\$")
+
+class MathBlockLexer(mistune.BlockLexer):
+    default_features = ['block_math'] + mistune.BlockLexer.default_features
+
+    def __init__(self, rules=None, **kwargs):
+        if rules is None:
+            rules = MathBlockGrammar()
+        super(MathBlockLexer, self).__init__(rules, **kwargs)
+
+    def parse_block_math(self, m):
+        """Parse a $$math$$ block"""
+        self.tokens.append({
+            'type': 'block_math',
+            'text': m.group(1)
+        })
+
+class MathInlineGrammar(mistune.InlineGrammar):
+    math = re.compile("^\$(.+?)\$")
+
+class MathInlineLexer(mistune.InlineLexer):
+    default_features = ['math'] + mistune.InlineLexer.default_features
+
+    def __init__(self, renderer, rules=None, **kwargs):
+        if rules is None:
+            rules = MathInlineGrammar()
+        super(MathInlineLexer, self).__init__(renderer, rules, **kwargs)
+
+    def output_math(self, m):
+        self.renderer.inline_math(m.group(1))
+
+class MarkdownWithMath(mistune.Markdown):
+    def __init__(self, renderer, **kwargs):
+        if 'inline' not in kwargs:
+            kwargs['inline'] = MathInlineLexer(renderer, **kwargs)
+        if 'block' not in kwargs:
+            kwargs['block'] = MathBlockLexer(**kwargs)
+        super(MarkdownWithMath, self).__init__(renderer, **kwargs)
+
+    def parse_block_math(self):
+        return self.renderer.block_math(self.token['text'])
 
 class MyRenderer(mistune.Renderer):
     def block_code(self, code, lang):
         if not lang:
             return '\n<pre><code>%s</code></pre>\n' % \
                 mistune.escape(code)
         lexer = get_lexer_by_name(lang, stripall=True)
         formatter = HtmlFormatter()
         return highlight(code, lexer, formatter)
 
+    # Pass math through unaltered - mathjax does the rendering in the browser
+    def block_math(self, text):
+        return '$$%s$$' % text
+
+    def inline_math(self, text):
+        return '$%s$' % text
+
 def markdown2html_mistune(source):
     """Convert a markdown string to HTML using mistune"""
-    return mistune.Markdown(renderer=MyRenderer()).render(source)
+    return MarkdownWithMath(renderer=MyRenderer()).render(source)
 
 def markdown2html_pandoc(source):
     """Convert a markdown string to HTML via pandoc"""
     return pandoc(source, 'markdown', 'html', extra_args=['--mathjax'])
 
 def _find_nodejs():
     global _node
     if _node is None:
         # prefer md2html via marked if node.js >= 0.9.12 is available
         # node is called nodejs on debian, so try that first
         _node = 'nodejs'
         if not _verify_node(_node):
             _node = 'node'
     return _node
 
 def markdown2html_marked(source, encoding='utf-8'):
     """Convert a markdown string to HTML via marked"""
     command = [_find_nodejs(), marked]
     try:
         p = subprocess.Popen(command,
                              stdin=subprocess.PIPE, stdout=subprocess.PIPE
         )
     except OSError as e:
         raise NodeJSMissing(
             "The command '%s' returned an error: %s.\n" % (" ".join(command), e) +
             "Please check that Node.js is installed."
         )
     out, _ = p.communicate(cast_bytes(source, encoding))
     out = TextIOWrapper(BytesIO(out), encoding, 'replace').read()
     return out.rstrip('\n')
 
 # The mistune renderer is the default, because it's simple to depend on it
-markdown2html = markdown2html_mistune
+markdown2html = markdown2html_marked
 
 def markdown2rst(source):
     """Convert a markdown string to ReST via pandoc.
 
     This function will raise an error if pandoc is not installed.
     Any error messages generated by pandoc are printed to stderr.
 
     Parameters
     ----------
     source : string
       Input string, assumed to be valid markdown.
 
     Returns
     -------
     out : string
       Output as returned by pandoc.
     """
     return pandoc(source, 'markdown', 'rst')
 
 def _verify_node(cmd):
     """Verify that the node command exists and is at least the minimum supported
     version of node.
 
     Parameters
     ----------
     cmd : string
         Node command to verify (i.e 'node')."""
     try:
         out, err, return_code = get_output_error_code([cmd, '--version'])
     except OSError:
         # Command not found
         return False
     if return_code:
         # Command error
         return False
     return check_version(out.lstrip('v'), '0.9.12')