Re-land "Check in a simple pure-python based Markdown previewer."

third_party/Python-Markdown/markdown/extensions/codehilite.py

+"""
+CodeHilite Extension for Python-Markdown
+========================================
+
+Adds code/syntax highlighting to standard Python-Markdown code blocks.
+
+See <https://pythonhosted.org/Markdown/extensions/code_hilite.html>
+for documentation.
+
+Original code Copyright 2006-2008 [Waylan Limberg](http://achinghead.com/).
+
+All changes Copyright 2008-2014 The Python Markdown Project
+
+License: [BSD](http://www.opensource.org/licenses/bsd-license.php)
+
+"""
+
+from __future__ import absolute_import
+from __future__ import unicode_literals
+from . import Extension
+from ..treeprocessors import Treeprocessor
+
+try:
+    from pygments import highlight
+    from pygments.lexers import get_lexer_by_name, guess_lexer
+    from pygments.formatters import get_formatter_by_name
+    pygments = True
+except ImportError:
+    pygments = False
+
+
+def parse_hl_lines(expr):
+    """Support our syntax for emphasizing certain lines of code.
+
+    expr should be like '1 2' to emphasize lines 1 and 2 of a code block.
+    Returns a list of ints, the line numbers to emphasize.
+    """
+    if not expr:
+        return []
+
+    try:
+        return list(map(int, expr.split()))
+    except ValueError:
+        return []
+
+
+# ------------------ The Main CodeHilite Class ----------------------
+class CodeHilite(object):
+    """
+    Determine language of source code, and pass it into pygments hilighter.
+
+    Basic Usage:
+        >>> code = CodeHilite(src = 'some text')
+        >>> html = code.hilite()
+
+    * src: Source string or any object with a .readline attribute.
+
+    * linenums: (Boolean) Set line numbering to 'on' (True),
+      'off' (False) or 'auto'(None). Set to 'auto' by default.
+
+    * guess_lang: (Boolean) Turn language auto-detection
+      'on' or 'off' (on by default).
+
+    * css_class: Set class name of wrapper div ('codehilite' by default).
+
+    * hl_lines: (List of integers) Lines to emphasize, 1-indexed.
+
+    Low Level Usage:
+        >>> code = CodeHilite()
+        >>> code.src = 'some text' # String or anything with a .readline attr.
+        >>> code.linenos = True  # Turns line numbering on or of.
+        >>> html = code.hilite()
+
+    """
+
+    def __init__(self, src=None, linenums=None, guess_lang=True,
+                 css_class="codehilite", lang=None, style='default',
+                 noclasses=False, tab_length=4, hl_lines=None, use_pygments=True):
+        self.src = src
+        self.lang = lang
+        self.linenums = linenums
+        self.guess_lang = guess_lang
+        self.css_class = css_class
+        self.style = style
+        self.noclasses = noclasses
+        self.tab_length = tab_length
+        self.hl_lines = hl_lines or []
+        self.use_pygments = use_pygments
+
+    def hilite(self):
+        """
+        Pass code to the [Pygments](http://pygments.pocoo.org/) highliter with
+        optional line numbers. The output should then be styled with css to
+        your liking. No styles are applied by default - only styling hooks
+        (i.e.: <span class="k">).
+
+        returns : A string of html.
+
+        """
+
+        self.src = self.src.strip('\n')
+
+        if self.lang is None:
+            self._parseHeader()
+
+        if pygments and self.use_pygments:
+            try:
+                lexer = get_lexer_by_name(self.lang)
+            except ValueError:
+                try:
+                    if self.guess_lang:
+                        lexer = guess_lexer(self.src)
+                    else:
+                        lexer = get_lexer_by_name('text')
+                except ValueError:
+                    lexer = get_lexer_by_name('text')
+            formatter = get_formatter_by_name('html',
+                                              linenos=self.linenums,
+                                              cssclass=self.css_class,
+                                              style=self.style,
+                                              noclasses=self.noclasses,
+                                              hl_lines=self.hl_lines)
+            return highlight(self.src, lexer, formatter)
+        else:
+            # just escape and build markup usable by JS highlighting libs
+            txt = self.src.replace('&', '&amp;')
+            txt = txt.replace('<', '&lt;')
+            txt = txt.replace('>', '&gt;')
+            txt = txt.replace('"', '&quot;')
+            classes = []
+            if self.lang:
+                classes.append('language-%s' % self.lang)
+            if self.linenums:
+                classes.append('linenums')
+            class_str = ''
+            if classes:
+                class_str = ' class="%s"' % ' '.join(classes)
+            return '<pre class="%s"><code%s>%s</code></pre>\n' % \
+                   (self.css_class, class_str, txt)
+
+    def _parseHeader(self):
+        """
+        Determines language of a code block from shebang line and whether said
+        line should be removed or left in place. If the sheband line contains a
+        path (even a single /) then it is assumed to be a real shebang line and
+        left alone. However, if no path is given (e.i.: #!python or :::python)
+        then it is assumed to be a mock shebang for language identifitation of
+        a code fragment and removed from the code block prior to processing for
+        code highlighting. When a mock shebang (e.i: #!python) is found, line
+        numbering is turned on. When colons are found in place of a shebang
+        (e.i.: :::python), line numbering is left in the current state - off
+        by default.
+
+        Also parses optional list of highlight lines, like:
+
+            :::python hl_lines="1 3"
+        """
+
+        import re
+
+        # split text into lines
+        lines = self.src.split("\n")
+        # pull first line to examine
+        fl = lines.pop(0)
+
+        c = re.compile(r'''
+            (?:(?:^::+)|(?P<shebang>^[#]!)) # Shebang or 2 or more colons
+            (?P<path>(?:/\w+)*[/ ])?        # Zero or 1 path
+            (?P<lang>[\w+-]*)               # The language
+            \s*                             # Arbitrary whitespace
+            # Optional highlight lines, single- or double-quote-delimited
+            (hl_lines=(?P<quot>"|')(?P<hl_lines>.*?)(?P=quot))?
+            ''',  re.VERBOSE)
+        # search first line for shebang
+        m = c.search(fl)
+        if m:
+            # we have a match
+            try:
+                self.lang = m.group('lang').lower()
+            except IndexError:
+                self.lang = None
+            if m.group('path'):
+                # path exists - restore first line
+                lines.insert(0, fl)
+            if self.linenums is None and m.group('shebang'):
+                # Overridable and Shebang exists - use line numbers
+                self.linenums = True
+
+            self.hl_lines = parse_hl_lines(m.group('hl_lines'))
+        else:
+            # No match
+            lines.insert(0, fl)
+
+        self.src = "\n".join(lines).strip("\n")
+
+
+# ------------------ The Markdown Extension -------------------------------
+
+
+class HiliteTreeprocessor(Treeprocessor):
+    """ Hilight source code in code blocks. """
+
+    def run(self, root):
+        """ Find code blocks and store in htmlStash. """
+        blocks = root.iter('pre')
+        for block in blocks:
+            if len(block) == 1 and block[0].tag == 'code':
+                code = CodeHilite(
+                    block[0].text,
+                    linenums=self.config['linenums'],
+                    guess_lang=self.config['guess_lang'],
+                    css_class=self.config['css_class'],
+                    style=self.config['pygments_style'],
+                    noclasses=self.config['noclasses'],
+                    tab_length=self.markdown.tab_length,
+                    use_pygments=self.config['use_pygments']
+                )
+                placeholder = self.markdown.htmlStash.store(code.hilite(),
+                                                            safe=True)
+                # Clear codeblock in etree instance
+                block.clear()
+                # Change to p element which will later
+                # be removed when inserting raw html
+                block.tag = 'p'
+                block.text = placeholder
+
+
+class CodeHiliteExtension(Extension):
+    """ Add source code hilighting to markdown codeblocks. """
+
+    def __init__(self, *args, **kwargs):
+        # define default configs
+        self.config = {
+            'linenums': [None,
+                         "Use lines numbers. True=yes, False=no, None=auto"],
+            'guess_lang': [True,
+                           "Automatic language detection - Default: True"],
+            'css_class': ["codehilite",
+                          "Set class name for wrapper <div> - "
+                          "Default: codehilite"],
+            'pygments_style': ['default',
+                               'Pygments HTML Formatter Style '
+                               '(Colorscheme) - Default: default'],
+            'noclasses': [False,
+                          'Use inline styles instead of CSS classes - '
+                          'Default false'],
+            'use_pygments': [True,
+                             'Use Pygments to Highlight code blocks. '
+                             'Disable if using a JavaScript library. '
+                             'Default: True']
+            }
+
+        super(CodeHiliteExtension, self).__init__(*args, **kwargs)
+
+    def extendMarkdown(self, md, md_globals):
+        """ Add HilitePostprocessor to Markdown instance. """
+        hiliter = HiliteTreeprocessor(md)
+        hiliter.config = self.getConfigs()
+        md.treeprocessors.add("hilite", hiliter, "<inline")
+
+        md.registerExtension(self)
+
+
+def makeExtension(*args, **kwargs):
+    return CodeHiliteExtension(*args, **kwargs)