Fix issue #5877 with tests

This pull request prevent to have lists environments inside the headings
cells which break latex code.

- First, the function `markdown2latex` has been changed in order to
  accept a markup keyword for pandoc reader, default to `markdown` as
  before(`test_markdown.py` updated too).
- Headings cells are treated with markup `markdown_strict+tex_math_dollars`
  to remove enhancements of pandoc for lists and add math support.
- Secondly, `prevent_list_blocks` filter escape characters `. - * +`
  in headings cells to prevent `enumerate` or `itemize` environments
  in latex sections(test added in `test_strings.py`

Test files accessible at:
    <https://gist.github.com/benjaminabel/4a40d1300dcf087c8695&gt;

IPython/nbconvert/exporters/templateexporter.py

@@ -62,6 +62,7 b' default_filters = {'
         'path2url': filters.path2url,
         'add_prompts': filters.add_prompts,
         'ascii_only': filters.ascii_only,
+        'prevent_list_blocks': filters.prevent_list_blocks,
 }
 
 #-----------------------------------------------------------------------------

IPython/nbconvert/filters/markdown.py

@@ -45,7 +45,7 b' class NodeJSMissing(ConversionException):'
     """Exception raised when node.js is missing."""
     pass
 
-def markdown2latex(source, extra_args=None):
+def markdown2latex(source, markup='markdown', extra_args=None):
     """Convert a markdown string to LaTeX via pandoc.
 
     This function will raise an error if pandoc is not installed.
@@ -55,13 +55,17 b' def markdown2latex(source, extra_args=None):'
     ----------
     source : string
       Input string, assumed to be valid markdown.
+    markup : string
+      Markup used by pandoc's reader
+      default : pandoc extended markdown
+      (see http://johnmacfarlane.net/pandoc/README.html#pandocs-markdown)
 
     Returns
     -------
     out : string
       Output as returned by pandoc.
     """
-    return pandoc(source, 'markdown', 'latex', extra_args=extra_args)
+    return pandoc(source, markup, 'latex', extra_args=extra_args)
 
 
 @undoc

IPython/nbconvert/filters/strings.py

@@ -45,6 +45,7 b' __all__ = ['
     'path2url',
     'add_prompts',
     'ascii_only',
+    'prevent_list_blocks',
 ]
 
 
@@ -218,4 +219,14 b' def path2url(path):'
 def ascii_only(s):
     """ensure a string is ascii"""
     s = py3compat.cast_unicode(s)
-    return s.encode('ascii', 'replace').decode('ascii')
  No newline at end of file
+    return s.encode('ascii', 'replace').decode('ascii')
+
+def prevent_list_blocks(s):
+    """
+    Prevent presence of enumerate or itemize blocks in latex headings cells
+    """
+    out = re.sub('(^\s*\d*)\.', '\\1\.', s)
+    out = re.sub('(^\s*)\-', '\\1\-', out)
+    out = re.sub('(^\s*)\+', '\\1\+', out)
+    out = re.sub('(^\s*)\*', '\\1\*', out)
+    return out

IPython/nbconvert/filters/tests/test_markdown.py

@@ -49,10 +49,24 b' class TestMarkdown(TestsBase):'
             self._try_markdown(markdown2latex, test, self.tokens[index])
 
     @dec.onlyif_cmds_exist('pandoc')
+    def test_markdown2latex_markup(self):
+        """markdown2latex with markup kwarg test"""
+        # This string should be passed through unaltered with pandoc's
+        # markdown_strict reader
+        s = '1) arabic number with parenthesis'
+        self.assertEqual(markdown2latex(s, markup='markdown_strict'), s)
+        # This string should be passed through unaltered with pandoc's
+        # markdown_strict+tex_math_dollars reader
+        s = '$\\alpha$ latex math'
+        self.assertEqual(
+            markdown2latex(s, markup='markdown_strict+tex_math_dollars'),
+            s)
+
+    @dec.onlyif_cmds_exist('pandoc')
     def test_pandoc_extra_args(self):
         # pass --no-wrap
         s = '\n'.join([
-            "#latex {{long_line | md2l(['--no-wrap'])}}",
+            "#latex {{long_line | md2l('markdown', ['--no-wrap'])}}",
             "#rst {{long_line | md2r(['--columns', '5'])}}",
         ])
         long_line = ' '.join(['long'] * 30)
@@ -64,7 +78,7 b' class TestMarkdown(TestsBase):'
         tpl = env.from_string(s)
         rendered = tpl.render(long_line=long_line)
         _, latex, rst = rendered.split('#')
-        
+
         self.assertEqual(latex.strip(), 'latex %s' % long_line)
         self.assertEqual(rst.strip(), 'rst %s' % long_line.replace(' ', '\n'))
 

IPython/nbconvert/filters/tests/test_strings.py

@@ -18,7 +18,7 b' import os'
 from ...tests.base import TestsBase
 from ..strings import (wrap_text, html2text, add_anchor, strip_dollars, 
     strip_files_prefix, get_lines, comment_lines, ipython2python, posix_path,
-    add_prompts
+    add_prompts, prevent_list_blocks
 )
 
 
@@ -151,3 +151,15 b' class TestStrings(TestsBase):'
         text1 = """for i in range(10):\n  i += 1\n  print i"""
         text2 = """>>> for i in range(10):\n...   i += 1\n...   print i"""
         self.assertEqual(text2, add_prompts(text1))
+
+    def test_prevent_list_blocks(self):
+        """prevent_list_blocks test"""
+        tests = [
+            ('1. arabic point', '1\\. arabic point'),
+            ('* bullet asterisk', '\\* bullet asterisk'),
+            ('+ bullet Plus Sign', '\\+ bullet Plus Sign'),
+            ('- bullet Hyphen-Minus', '\\- bullet Hyphen-Minus'),
+            ('  1. spaces + arabic point', '  1\\. spaces + arabic point'),
+        ]
+        for test in tests:
+            self.assertEqual(prevent_list_blocks(test[0]), test[1])

IPython/nbconvert/templates/latex/base.tplx

@@ -201,7 +201,8 b' This template does not define a docclass, the inheriting class must define this.'
     ((* elif cell.level == 6 -*))
         ((* block h6 -*))\\*\textit((* endblock h6 -*))
     ((*- endif -*))
-    {((( cell.source | replace('\n', ' ') | citation2latex | strip_files_prefix | markdown2latex )))}
+    {((( cell.source | replace('\n', ' ') | citation2latex | strip_files_prefix | prevent_list_blocks | markdown2latex(markup='markdown_strict+tex_math_dollars') )))}
+    
 
 ((* endblock headingcell *))