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

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

Index: third_party/Python-Markdown/markdown/extensions/attr_list.py
diff --git a/third_party/Python-Markdown/markdown/extensions/attr_list.py b/third_party/Python-Markdown/markdown/extensions/attr_list.py
new file mode 100644
index 0000000000000000000000000000000000000000..683bdf831c0d55b3740a4bd8f89d1cbdf9c51caa
--- /dev/null
+++ b/third_party/Python-Markdown/markdown/extensions/attr_list.py
@@ -0,0 +1,177 @@
+"""
+Attribute List Extension for Python-Markdown
+============================================
+
+Adds attribute list syntax. Inspired by
+[maruku](http://maruku.rubyforge.org/proposal.html#attribute_lists)'s
+feature of the same name.
+
+See <https://pythonhosted.org/Markdown/extensions/attr_list.html>
+for documentation.
+
+Original code Copyright 2011 [Waylan Limberg](http://achinghead.com/).
+
+All changes Copyright 2011-2014 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
+from ..util import isBlockLevel
+import re
+
+try:
+    Scanner = re.Scanner
+except AttributeError:  # pragma: no cover
+    # must be on Python 2.4
+    from sre import Scanner
+
+
+def _handle_double_quote(s, t):
+    k, v = t.split('=')
+    return k, v.strip('"')
+
+
+def _handle_single_quote(s, t):
+    k, v = t.split('=')
+    return k, v.strip("'")
+
+
+def _handle_key_value(s, t):
+    return t.split('=')
+
+
+def _handle_word(s, t):
+    if t.startswith('.'):
+        return '.', t[1:]
+    if t.startswith('#'):
+        return 'id', t[1:]
+    return t, t
+
+_scanner = Scanner([
+    (r'[^ ]+=".*?"', _handle_double_quote),
+    (r"[^ ]+='.*?'", _handle_single_quote),
+    (r'[^ ]+=[^ =]+', _handle_key_value),
+    (r'[^ =]+', _handle_word),
+    (r' ', None)
+])
+
+
+def get_attrs(str):
+    """ Parse attribute list and return a list of attribute tuples. """
+    return _scanner.scan(str)[0]
+
+
+def isheader(elem):
+    return elem.tag in ['h1', 'h2', 'h3', 'h4', 'h5', 'h6']
+
+
+class AttrListTreeprocessor(Treeprocessor):
+
+    BASE_RE = r'\{\:?([^\}]*)\}'
+    HEADER_RE = re.compile(r'[ ]+%s[ ]*$' % BASE_RE)
+    BLOCK_RE = re.compile(r'\n[ ]*%s[ ]*$' % BASE_RE)
+    INLINE_RE = re.compile(r'^%s' % BASE_RE)
+    NAME_RE = re.compile(r'[^A-Z_a-z\u00c0-\u00d6\u00d8-\u00f6\u00f8-\u02ff'
+                         r'\u0370-\u037d\u037f-\u1fff\u200c-\u200d'
+                         r'\u2070-\u218f\u2c00-\u2fef\u3001-\ud7ff'
+                         r'\uf900-\ufdcf\ufdf0-\ufffd'
+                         r'\:\-\.0-9\u00b7\u0300-\u036f\u203f-\u2040]+')
+
+    def run(self, doc):
+        for elem in doc.getiterator():
+            if isBlockLevel(elem.tag):
+                # Block level: check for attrs on last line of text
+                RE = self.BLOCK_RE
+                if isheader(elem) or elem.tag == 'dt':
+                    # header or def-term: check for attrs at end of line
+                    RE = self.HEADER_RE
+                if len(elem) and elem.tag == 'li':
+                    # special case list items. children may include a ul or ol.
+                    pos = None
+                    # find the ul or ol position
+                    for i, child in enumerate(elem):
+                        if child.tag in ['ul', 'ol']:
+                            pos = i
+                            break
+                    if pos is None and elem[-1].tail:
+                        # use tail of last child. no ul or ol.
+                        m = RE.search(elem[-1].tail)
+                        if m:
+                            self.assign_attrs(elem, m.group(1))
+                            elem[-1].tail = elem[-1].tail[:m.start()]
+                    elif pos is not None and pos > 0 and elem[pos-1].tail:
+                        # use tail of last child before ul or ol
+                        m = RE.search(elem[pos-1].tail)
+                        if m:
+                            self.assign_attrs(elem, m.group(1))
+                            elem[pos-1].tail = elem[pos-1].tail[:m.start()]
+                    elif elem.text:
+                        # use text. ul is first child.
+                        m = RE.search(elem.text)
+                        if m:
+                            self.assign_attrs(elem, m.group(1))
+                            elem.text = elem.text[:m.start()]
+                elif len(elem) and elem[-1].tail:
+                    # has children. Get from tail of last child
+                    m = RE.search(elem[-1].tail)
+                    if m:
+                        self.assign_attrs(elem, m.group(1))
+                        elem[-1].tail = elem[-1].tail[:m.start()]
+                        if isheader(elem):
+                            # clean up trailing #s
+                            elem[-1].tail = elem[-1].tail.rstrip('#').rstrip()
+                elif elem.text:
+                    # no children. Get from text.
+                    m = RE.search(elem.text)
+                    if not m and elem.tag == 'td':
+                        m = re.search(self.BASE_RE, elem.text)
+                    if m:
+                        self.assign_attrs(elem, m.group(1))
+                        elem.text = elem.text[:m.start()]
+                        if isheader(elem):
+                            # clean up trailing #s
+                            elem.text = elem.text.rstrip('#').rstrip()
+            else:
+                # inline: check for attrs at start of tail
+                if elem.tail:
+                    m = self.INLINE_RE.match(elem.tail)
+                    if m:
+                        self.assign_attrs(elem, m.group(1))
+                        elem.tail = elem.tail[m.end():]
+
+    def assign_attrs(self, elem, attrs):
+        """ Assign attrs to element. """
+        for k, v in get_attrs(attrs):
+            if k == '.':
+                # add to class
+                cls = elem.get('class')
+                if cls:
+                    elem.set('class', '%s %s' % (cls, v))
+                else:
+                    elem.set('class', v)
+            else:
+                # assign attr k with v
+                elem.set(self.sanitize_name(k), v)
+
+    def sanitize_name(self, name):
+        """
+        Sanitize name as 'an XML Name, minus the ":"'.
+        See http://www.w3.org/TR/REC-xml-names/#NT-NCName
+        """
+        return self.NAME_RE.sub('_', name)
+
+
+class AttrListExtension(Extension):
+    def extendMarkdown(self, md, md_globals):
+        md.treeprocessors.add(
+            'attr_list', AttrListTreeprocessor(md), '>prettify'
+        )
+
+
+def makeExtension(*args, **kwargs):
+    return AttrListExtension(*args, **kwargs)