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

third_party/Python-Markdown/markdown/__init__.py

Index: third_party/Python-Markdown/markdown/__init__.py
diff --git a/third_party/Python-Markdown/markdown/__init__.py b/third_party/Python-Markdown/markdown/__init__.py
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+"""
+Python Markdown
+===============
+
+Python Markdown converts Markdown to HTML and can be used as a library or
+called from the command line.
+
+## Basic usage as a module:
+
+    import markdown
+    html = markdown.markdown(your_text_string)
+
+See <https://pythonhosted.org/Markdown/> for more
+information and instructions on how to extend the functionality of
+Python Markdown.  Read that before you try modifying this file.
+
+## Authors and License
+
+Started by [Manfred Stienstra](http://www.dwerg.net/).  Continued and
+maintained  by [Yuri Takhteyev](http://www.freewisdom.org), [Waylan
+Limberg](http://achinghead.com/) and [Artem Yunusov](http://blog.splyer.com).
+
+Contact: markdown@freewisdom.org
+
+Copyright 2007-2013 The Python Markdown Project (v. 1.7 and later)
+Copyright 200? Django Software Foundation (OrderedDict implementation)
+Copyright 2004, 2005, 2006 Yuri Takhteyev (v. 0.2-1.6b)
+Copyright 2004 Manfred Stienstra (the original version)
+
+License: BSD (see LICENSE for details).
+"""
+
+from __future__ import absolute_import
+from __future__ import unicode_literals
+from .__version__ import version, version_info  # noqa
+import codecs
+import sys
+import logging
+import warnings
+import importlib
+from . import util
+from .preprocessors import build_preprocessors
+from .blockprocessors import build_block_parser
+from .treeprocessors import build_treeprocessors
+from .inlinepatterns import build_inlinepatterns
+from .postprocessors import build_postprocessors
+from .extensions import Extension
+from .serializers import to_html_string, to_xhtml_string
+
+__all__ = ['Markdown', 'markdown', 'markdownFromFile']
+
+
+logger = logging.getLogger('MARKDOWN')
+
+
+class Markdown(object):
+    """Convert Markdown to HTML."""
+
+    doc_tag = "div"     # Element used to wrap document - later removed
+
+    option_defaults = {
+        'html_replacement_text': '[HTML_REMOVED]',
+        'tab_length':            4,
+        'enable_attributes':     True,
+        'smart_emphasis':        True,
+        'lazy_ol':               True,
+    }
+
+    output_formats = {
+        'html':   to_html_string,
+        'html4':  to_html_string,
+        'html5':  to_html_string,
+        'xhtml':  to_xhtml_string,
+        'xhtml1': to_xhtml_string,
+        'xhtml5': to_xhtml_string,
+    }
+
+    ESCAPED_CHARS = ['\\', '`', '*', '_', '{', '}', '[', ']',
+                     '(', ')', '>', '#', '+', '-', '.', '!']
+
+    def __init__(self, *args, **kwargs):
+        """
+        Creates a new Markdown instance.
+
+        Keyword arguments:
+
+        * extensions: A list of extensions.
+           If they are of type string, the module mdx_name.py will be loaded.
+           If they are a subclass of markdown.Extension, they will be used
+           as-is.
+        * extension_configs: Configuration settings for extensions.
+        * output_format: Format of output. Supported formats are:
+            * "xhtml1": Outputs XHTML 1.x. Default.
+            * "xhtml5": Outputs XHTML style tags of HTML 5
+            * "xhtml": Outputs latest supported version of XHTML
+              (currently XHTML 1.1).
+            * "html4": Outputs HTML 4
+            * "html5": Outputs HTML style tags of HTML 5
+            * "html": Outputs latest supported version of HTML
+              (currently HTML 4).
+            Note that it is suggested that the more specific formats ("xhtml1"
+            and "html4") be used as "xhtml" or "html" may change in the future
+            if it makes sense at that time.
+        * safe_mode: Deprecated! Disallow raw html. One of "remove", "replace"
+          or "escape".
+        * html_replacement_text: Deprecated! Text used when safe_mode is set
+          to "replace".
+        * tab_length: Length of tabs in the source. Default: 4
+        * enable_attributes: Enable the conversion of attributes. Default: True
+        * smart_emphasis: Treat `_connected_words_` intelligently Default: True
+        * lazy_ol: Ignore number of first item of ordered lists. Default: True
+
+        """
+
+        # For backward compatibility, loop through old positional args
+        pos = ['extensions', 'extension_configs', 'safe_mode', 'output_format']
+        for c, arg in enumerate(args):
+            if pos[c] not in kwargs:
+                kwargs[pos[c]] = arg
+            if c+1 == len(pos):  # pragma: no cover
+                # ignore any additional args
+                break
+        if len(args):
+            warnings.warn('Positional arguments are deprecated in Markdown. '
+                          'Use keyword arguments only.',
+                          DeprecationWarning)
+
+        # Loop through kwargs and assign defaults
+        for option, default in self.option_defaults.items():
+            setattr(self, option, kwargs.get(option, default))
+
+        self.safeMode = kwargs.get('safe_mode', False)
+        if self.safeMode and 'enable_attributes' not in kwargs:
+            # Disable attributes in safeMode when not explicitly set
+            self.enable_attributes = False
+
+        if 'safe_mode' in kwargs:
+            warnings.warn('"safe_mode" is deprecated in Python-Markdown. '
+                          'Use an HTML sanitizer (like '
+                          'Bleach http://bleach.readthedocs.org/) '
+                          'if you are parsing untrusted markdown text. '
+                          'See the 2.6 release notes for more info',
+                          DeprecationWarning)
+
+        if 'html_replacement_text' in kwargs:
+            warnings.warn('The "html_replacement_text" keyword is '
+                          'deprecated along with "safe_mode".',
+                          DeprecationWarning)
+
+        self.registeredExtensions = []
+        self.docType = ""
+        self.stripTopLevelTags = True
+
+        self.build_parser()
+
+        self.references = {}
+        self.htmlStash = util.HtmlStash()
+        self.registerExtensions(extensions=kwargs.get('extensions', []),
+                                configs=kwargs.get('extension_configs', {}))
+        self.set_output_format(kwargs.get('output_format', 'xhtml1'))
+        self.reset()
+
+    def build_parser(self):
+        """ Build the parser from the various parts. """
+        self.preprocessors = build_preprocessors(self)
+        self.parser = build_block_parser(self)
+        self.inlinePatterns = build_inlinepatterns(self)
+        self.treeprocessors = build_treeprocessors(self)
+        self.postprocessors = build_postprocessors(self)
+        return self
+
+    def registerExtensions(self, extensions, configs):
+        """
+        Register extensions with this instance of Markdown.
+
+        Keyword arguments:
+
+        * extensions: A list of extensions, which can either
+           be strings or objects.  See the docstring on Markdown.
+        * configs: A dictionary mapping module names to config options.
+
+        """
+        for ext in extensions:
+            if isinstance(ext, util.string_type):
+                ext = self.build_extension(ext, configs.get(ext, {}))
+            if isinstance(ext, Extension):
+                ext.extendMarkdown(self, globals())
+                logger.debug(
+                    'Successfully loaded extension "%s.%s".'
+                    % (ext.__class__.__module__, ext.__class__.__name__)
+                )
+            elif ext is not None:
+                raise TypeError(
+                    'Extension "%s.%s" must be of type: "markdown.Extension"'
+                    % (ext.__class__.__module__, ext.__class__.__name__))
+
+        return self
+
+    def build_extension(self, ext_name, configs):
+        """Build extension by name, then return the module.
+
+        The extension name may contain arguments as part of the string in the
+        following format: "extname(key1=value1,key2=value2)"
+
+        """
+
+        configs = dict(configs)
+
+        # Parse extensions config params (ignore the order)
+        pos = ext_name.find("(")  # find the first "("
+        if pos > 0:
+            ext_args = ext_name[pos+1:-1]
+            ext_name = ext_name[:pos]
+            pairs = [x.split("=") for x in ext_args.split(",")]
+            configs.update([(x.strip(), y.strip()) for (x, y) in pairs])
+            warnings.warn('Setting configs in the Named Extension string is '
+                          'deprecated. It is recommended that you '
+                          'pass an instance of the extension class to '
+                          'Markdown or use the "extension_configs" keyword. '
+                          'The current behavior will raise an error in version 2.7. '
+                          'See the Release Notes for Python-Markdown version '
+                          '2.6 for more info.', DeprecationWarning)
+
+        # Get class name (if provided): `path.to.module:ClassName`
+        ext_name, class_name = ext_name.split(':', 1) \
+            if ':' in ext_name else (ext_name, '')
+
+        # Try loading the extension first from one place, then another
+        try:
+            # Assume string uses dot syntax (`path.to.some.module`)
+            module = importlib.import_module(ext_name)
+            logger.debug(
+                'Successfuly imported extension module "%s".' % ext_name
+            )
+            # For backward compat (until deprecation)
+            # check that this is an extension.
+            if ('.' not in ext_name and not (hasattr(module, 'makeExtension') or
+               (class_name and hasattr(module, class_name)))):
+                # We have a name conflict
+                # eg: extensions=['tables'] and PyTables is installed
+                raise ImportError
+        except ImportError:
+            # Preppend `markdown.extensions.` to name
+            module_name = '.'.join(['markdown.extensions', ext_name])
+            try:
+                module = importlib.import_module(module_name)
+                logger.debug(
+                    'Successfuly imported extension module "%s".' %
+                    module_name
+                )
+                warnings.warn('Using short names for Markdown\'s builtin '
+                              'extensions is deprecated. Use the '
+                              'full path to the extension with Python\'s dot '
+                              'notation (eg: "%s" instead of "%s"). The '
+                              'current behavior will raise an error in version '
+                              '2.7. See the Release Notes for '
+                              'Python-Markdown version 2.6 for more info.' %
+                              (module_name, ext_name),
+                              DeprecationWarning)
+            except ImportError:
+                # Preppend `mdx_` to name
+                module_name_old_style = '_'.join(['mdx', ext_name])
+                try:
+                    module = importlib.import_module(module_name_old_style)
+                    logger.debug(
+                        'Successfuly imported extension module "%s".' %
+                        module_name_old_style)
+                    warnings.warn('Markdown\'s behavior of prepending "mdx_" '
+                                  'to an extension name is deprecated. '
+                                  'Use the full path to the '
+                                  'extension with Python\'s dot notation '
+                                  '(eg: "%s" instead of "%s"). The current '
+                                  'behavior will raise an error in version 2.7. '
+                                  'See the Release Notes for Python-Markdown '
+                                  'version 2.6 for more info.' %
+                                  (module_name_old_style, ext_name),
+                                  DeprecationWarning)
+                except ImportError as e:
+                    message = "Failed loading extension '%s' from '%s', '%s' " \
+                        "or '%s'" % (ext_name, ext_name, module_name,
+                                     module_name_old_style)
+                    e.args = (message,) + e.args[1:]
+                    raise
+
+        if class_name:
+            # Load given class name from module.
+            return getattr(module, class_name)(**configs)
+        else:
+            # Expect  makeExtension() function to return a class.
+            try:
+                return module.makeExtension(**configs)
+            except AttributeError as e:
+                message = e.args[0]
+                message = "Failed to initiate extension " \
+                          "'%s': %s" % (ext_name, message)
+                e.args = (message,) + e.args[1:]
+                raise
+
+    def registerExtension(self, extension):
+        """ This gets called by the extension """
+        self.registeredExtensions.append(extension)
+        return self
+
+    def reset(self):
+        """
+        Resets all state variables so that we can start with a new text.
+        """
+        self.htmlStash.reset()
+        self.references.clear()
+
+        for extension in self.registeredExtensions:
+            if hasattr(extension, 'reset'):
+                extension.reset()
+
+        return self
+
+    def set_output_format(self, format):
+        """ Set the output format for the class instance. """
+        self.output_format = format.lower()
+        try:
+            self.serializer = self.output_formats[self.output_format]
+        except KeyError as e:
+            valid_formats = list(self.output_formats.keys())
+            valid_formats.sort()
+            message = 'Invalid Output Format: "%s". Use one of %s.' \
+                % (self.output_format,
+                   '"' + '", "'.join(valid_formats) + '"')
+            e.args = (message,) + e.args[1:]
+            raise
+        return self
+
+    def convert(self, source):
+        """
+        Convert markdown to serialized XHTML or HTML.
+
+        Keyword arguments:
+
+        * source: Source text as a Unicode string.
+
+        Markdown processing takes place in five steps:
+
+        1. A bunch of "preprocessors" munge the input text.
+        2. BlockParser() parses the high-level structural elements of the
+           pre-processed text into an ElementTree.
+        3. A bunch of "treeprocessors" are run against the ElementTree. One
+           such treeprocessor runs InlinePatterns against the ElementTree,
+           detecting inline markup.
+        4. Some post-processors are run against the text after the ElementTree
+           has been serialized into text.
+        5. The output is written to a string.
+
+        """
+
+        # Fixup the source text
+        if not source.strip():
+            return ''  # a blank unicode string
+
+        try:
+            source = util.text_type(source)
+        except UnicodeDecodeError as e:
+            # Customise error message while maintaining original trackback
+            e.reason += '. -- Note: Markdown only accepts unicode input!'
+            raise
+
+        # Split into lines and run the line preprocessors.
+        self.lines = source.split("\n")
+        for prep in self.preprocessors.values():
+            self.lines = prep.run(self.lines)
+
+        # Parse the high-level elements.
+        root = self.parser.parseDocument(self.lines).getroot()
+
+        # Run the tree-processors
+        for treeprocessor in self.treeprocessors.values():
+            newRoot = treeprocessor.run(root)
+            if newRoot is not None:
+                root = newRoot
+
+        # Serialize _properly_.  Strip top-level tags.
+        output = self.serializer(root)
+        if self.stripTopLevelTags:
+            try:
+                start = output.index(
+                    '<%s>' % self.doc_tag) + len(self.doc_tag) + 2
+                end = output.rindex('</%s>' % self.doc_tag)
+                output = output[start:end].strip()
+            except ValueError:  # pragma: no cover
+                if output.strip().endswith('<%s />' % self.doc_tag):
+                    # We have an empty document
+                    output = ''
+                else:
+                    # We have a serious problem
+                    raise ValueError('Markdown failed to strip top-level '
+                                     'tags. Document=%r' % output.strip())
+
+        # Run the text post-processors
+        for pp in self.postprocessors.values():
+            output = pp.run(output)
+
+        return output.strip()
+
+    def convertFile(self, input=None, output=None, encoding=None):
+        """Converts a Markdown file and returns the HTML as a Unicode string.
+
+        Decodes the file using the provided encoding (defaults to utf-8),
+        passes the file content to markdown, and outputs the html to either
+        the provided stream or the file with provided name, using the same
+        encoding as the source file. The 'xmlcharrefreplace' error handler is
+        used when encoding the output.
+
+        **Note:** This is the only place that decoding and encoding of Unicode
+        takes place in Python-Markdown.  (All other code is Unicode-in /
+        Unicode-out.)
+
+        Keyword arguments:
+
+        * input: File object or path. Reads from stdin if `None`.
+        * output: File object or path. Writes to stdout if `None`.
+        * encoding: Encoding of input and output files. Defaults to utf-8.
+
+        """
+
+        encoding = encoding or "utf-8"
+
+        # Read the source
+        if input:
+            if isinstance(input, util.string_type):
+                input_file = codecs.open(input, mode="r", encoding=encoding)
+            else:
+                input_file = codecs.getreader(encoding)(input)
+            text = input_file.read()
+            input_file.close()
+        else:
+            text = sys.stdin.read()
+            if not isinstance(text, util.text_type):
+                text = text.decode(encoding)
+
+        text = text.lstrip('\ufeff')  # remove the byte-order mark
+
+        # Convert
+        html = self.convert(text)
+
+        # Write to file or stdout
+        if output:
+            if isinstance(output, util.string_type):
+                output_file = codecs.open(output, "w",
+                                          encoding=encoding,
+                                          errors="xmlcharrefreplace")
+                output_file.write(html)
+                output_file.close()
+            else:
+                writer = codecs.getwriter(encoding)
+                output_file = writer(output, errors="xmlcharrefreplace")
+                output_file.write(html)
+                # Don't close here. User may want to write more.
+        else:
+            # Encode manually and write bytes to stdout.
+            html = html.encode(encoding, "xmlcharrefreplace")
+            try:
+                # Write bytes directly to buffer (Python 3).
+                sys.stdout.buffer.write(html)
+            except AttributeError:
+                # Probably Python 2, which works with bytes by default.
+                sys.stdout.write(html)
+
+        return self
+
+
+"""
+EXPORTED FUNCTIONS
+=============================================================================
+
+Those are the two functions we really mean to export: markdown() and
+markdownFromFile().
+"""
+
+
+def markdown(text, *args, **kwargs):
+    """Convert a Markdown string to HTML and return HTML as a Unicode string.
+
+    This is a shortcut function for `Markdown` class to cover the most
+    basic use case.  It initializes an instance of Markdown, loads the
+    necessary extensions and runs the parser on the given text.
+
+    Keyword arguments:
+
+    * text: Markdown formatted text as Unicode or ASCII string.
+    * Any arguments accepted by the Markdown class.
+
+    Returns: An HTML document as a string.
+
+    """
+    md = Markdown(*args, **kwargs)
+    return md.convert(text)
+
+
+def markdownFromFile(*args, **kwargs):
+    """Read markdown code from a file and write it to a file or a stream.
+
+    This is a shortcut function which initializes an instance of Markdown,
+    and calls the convertFile method rather than convert.
+
+    Keyword arguments:
+
+    * input: a file name or readable object.
+    * output: a file name or writable object.
+    * encoding: Encoding of input and output.
+    * Any arguments accepted by the Markdown class.
+
+    """
+    # For backward compatibility loop through positional args
+    pos = ['input', 'output', 'extensions', 'encoding']
+    c = 0
+    for arg in args:
+        if pos[c] not in kwargs:
+            kwargs[pos[c]] = arg
+        c += 1
+        if c == len(pos):
+            break
+    if len(args):
+        warnings.warn('Positional arguments are depreacted in '
+                      'Markdown and will raise an error in version 2.7. '
+                      'Use keyword arguments only.',
+                      DeprecationWarning)
+
+    md = Markdown(**kwargs)
+    md.convertFile(kwargs.get('input', None),
+                   kwargs.get('output', None),
+                   kwargs.get('encoding', None))