Clean up codebase and improve file loading

- Moved plugins to proper sub groups (autopairs, code_minimap, colorize, commentzar, info_bar, markdown_preview, prettify_json, search_replace, tabs_bar, telescope, toggle_source_view, lsp_client)
- Add filter_out_loaded_files to prevent opening already-loaded files
- Add INDEPENDENT source view state
- Fix cursor scroll position on buffer switch
- Fix signal blocking during file load
- Fix word boundary in completion provider
- Refactor code events into single events module

plugins/code/ui/markdown_preview/markdown/extensions/__init__.py

@@ -0,0 +1,145 @@
+# Python Markdown
+
+# A Python implementation of John Gruber's Markdown.
+
+# Documentation: https://python-markdown.github.io/
+# GitHub: https://github.com/Python-Markdown/markdown/
+# PyPI: https://pypi.org/project/Markdown/
+
+# Started by Manfred Stienstra (http://www.dwerg.net/).
+# Maintained for a few years by Yuri Takhteyev (http://www.freewisdom.org).
+# Currently maintained by Waylan Limberg (https://github.com/waylan),
+# Dmitry Shachnev (https://github.com/mitya57) and Isaac Muse (https://github.com/facelessuser).
+
+# Copyright 2007-2023 The Python Markdown Project (v. 1.7 and later)
+# Copyright 2004, 2005, 2006 Yuri Takhteyev (v. 0.2-1.6b)
+# Copyright 2004 Manfred Stienstra (the original version)
+
+# License: BSD (see LICENSE.md for details).
+
+"""
+Markdown accepts an [`Extension`][markdown.extensions.Extension] instance for each extension. Therefore, each extension
+must to define a class that extends [`Extension`][markdown.extensions.Extension] and over-rides the
+[`extendMarkdown`][markdown.extensions.Extension.extendMarkdown] method. Within this class one can manage configuration
+options for their extension and attach the various processors and patterns which make up an extension to the
+[`Markdown`][markdown.Markdown] instance.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Any, Mapping, Sequence
+from ..util import parseBoolValue
+
+if TYPE_CHECKING:  # pragma: no cover
+    from markdown import Markdown
+
+
+class Extension:
+    """ Base class for extensions to subclass. """
+
+    config: Mapping[str, list] = {}
+    """
+    Default configuration for an extension.
+
+    This attribute is to be defined in a subclass and must be of the following format:
+
+    ``` python
+    config = {
+        'key': ['value', 'description']
+    }
+    ```
+
+    Note that [`setConfig`][markdown.extensions.Extension.setConfig] will raise a [`KeyError`][]
+    if a default is not set for each option.
+    """
+
+    def __init__(self, **kwargs):
+        """ Initiate Extension and set up configs. """
+        self.setConfigs(kwargs)
+
+    def getConfig(self, key: str, default: Any = '') -> Any:
+        """
+        Return a single configuration option value.
+
+        Arguments:
+            key: The configuration option name.
+            default: Default value to return if key is not set.
+
+        Returns:
+            Value of stored configuration option.
+        """
+        if key in self.config:
+            return self.config[key][0]
+        else:
+            return default
+
+    def getConfigs(self) -> dict[str, Any]:
+        """
+        Return all configuration options.
+
+        Returns:
+            All configuration options.
+        """
+        return {key: self.getConfig(key) for key in self.config.keys()}
+
+    def getConfigInfo(self) -> list[tuple[str, str]]:
+        """
+        Return descriptions of all configuration options.
+
+        Returns:
+            All descriptions of configuration options.
+        """
+        return [(key, self.config[key][1]) for key in self.config.keys()]
+
+    def setConfig(self, key: str, value: Any) -> None:
+        """
+        Set a configuration option.
+
+        If the corresponding default value set in [`config`][markdown.extensions.Extension.config]
+        is a `bool` value or `None`, then `value` is passed through
+        [`parseBoolValue`][markdown.util.parseBoolValue] before being stored.
+
+        Arguments:
+            key: Name of configuration option to set.
+            value: Value to assign to option.
+
+        Raises:
+            KeyError: If `key` is not known.
+        """
+        if isinstance(self.config[key][0], bool):
+            value = parseBoolValue(value)
+        if self.config[key][0] is None:
+            value = parseBoolValue(value, preserve_none=True)
+        self.config[key][0] = value
+
+    def setConfigs(self, items: Mapping[str, Any] | Sequence[tuple[str, Any]]):
+        """
+        Loop through a collection of configuration options, passing each to
+        [`setConfig`][markdown.extensions.Extension.setConfig].
+
+        Arguments:
+            items: Collection of configuration options.
+
+        Raises:
+            KeyError: for any unknown key.
+        """
+        if hasattr(items, 'items'):
+            # it's a dict
+            items = items.items()
+        for key, value in items:
+            self.setConfig(key, value)
+
+    def extendMarkdown(self, md: Markdown) -> None:
+        """
+        Add the various processors and patterns to the Markdown Instance.
+
+        This method must be overridden by every extension.
+
+        Arguments:
+            md: The Markdown instance.
+
+        """
+        raise NotImplementedError(
+            'Extension "%s.%s" must define an "extendMarkdown"'
+            'method.' % (self.__class__.__module__, self.__class__.__name__)
+        )

plugins/code/ui/markdown_preview/markdown/extensions/abbr.py

@@ -0,0 +1,105 @@
+# Abbreviation Extension for Python-Markdown
+# ==========================================
+
+# This extension adds abbreviation handling to Python-Markdown.
+
+# See https://Python-Markdown.github.io/extensions/abbreviations
+# for documentation.
+
+# Original code Copyright 2007-2008 [Waylan Limberg](http://achinghead.com/)
+# and [Seemant Kulleen](http://www.kulleen.org/)
+
+# All changes Copyright 2008-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+This extension adds abbreviation handling to Python-Markdown.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/abbreviations)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..blockprocessors import BlockProcessor
+from ..inlinepatterns import InlineProcessor
+from ..util import AtomicString
+import re
+import xml.etree.ElementTree as etree
+
+
+class AbbrExtension(Extension):
+    """ Abbreviation Extension for Python-Markdown. """
+
+    def extendMarkdown(self, md):
+        """ Insert `AbbrPreprocessor` before `ReferencePreprocessor`. """
+        md.parser.blockprocessors.register(AbbrPreprocessor(md.parser), 'abbr', 16)
+
+
+class AbbrPreprocessor(BlockProcessor):
+    """ Abbreviation Preprocessor - parse text for abbr references. """
+
+    RE = re.compile(r'^[*]\[(?P<abbr>[^\]]*)\][ ]?:[ ]*\n?[ ]*(?P<title>.*)$', re.MULTILINE)
+
+    def test(self, parent, block):
+        return True
+
+    def run(self, parent, blocks):
+        """
+        Find and remove all Abbreviation references from the text.
+        Each reference is set as a new `AbbrPattern` in the markdown instance.
+
+        """
+        block = blocks.pop(0)
+        m = self.RE.search(block)
+        if m:
+            abbr = m.group('abbr').strip()
+            title = m.group('title').strip()
+            self.parser.md.inlinePatterns.register(
+                AbbrInlineProcessor(self._generate_pattern(abbr), title), 'abbr-%s' % abbr, 2
+            )
+            if block[m.end():].strip():
+                # Add any content after match back to blocks as separate block
+                blocks.insert(0, block[m.end():].lstrip('\n'))
+            if block[:m.start()].strip():
+                # Add any content before match back to blocks as separate block
+                blocks.insert(0, block[:m.start()].rstrip('\n'))
+            return True
+        # No match. Restore block.
+        blocks.insert(0, block)
+        return False
+
+    def _generate_pattern(self, text):
+        """
+        Given a string, returns an regex pattern to match that string.
+
+        'HTML' -> r'(?P<abbr>[H][T][M][L])'
+
+        Note: we force each char as a literal match (in brackets) as we don't
+        know what they will be beforehand.
+
+        """
+        chars = list(text)
+        for i in range(len(chars)):
+            chars[i] = r'[%s]' % chars[i]
+        return r'(?P<abbr>\b%s\b)' % (r''.join(chars))
+
+
+class AbbrInlineProcessor(InlineProcessor):
+    """ Abbreviation inline pattern. """
+
+    def __init__(self, pattern, title):
+        super().__init__(pattern)
+        self.title = title
+
+    def handleMatch(self, m, data):
+        abbr = etree.Element('abbr')
+        abbr.text = AtomicString(m.group('abbr'))
+        abbr.set('title', self.title)
+        return abbr, m.start(0), m.end(0)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return AbbrExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/admonition.py

@@ -0,0 +1,179 @@
+# Admonition extension for Python-Markdown
+# ========================================
+
+# Adds rST-style admonitions. Inspired by [rST][] feature with the same name.
+
+# [rST]: http://docutils.sourceforge.net/docs/ref/rst/directives.html#specific-admonitions
+
+# See https://Python-Markdown.github.io/extensions/admonition
+# for documentation.
+
+# Original code Copyright [Tiago Serafim](https://www.tiagoserafim.com/).
+
+# All changes Copyright The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+
+"""
+Adds rST-style admonitions. Inspired by [rST][] feature with the same name.
+
+[rST]: http://docutils.sourceforge.net/docs/ref/rst/directives.html#specific-admonitions
+
+See the [documentation](https://Python-Markdown.github.io/extensions/admonition)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..blockprocessors import BlockProcessor
+import xml.etree.ElementTree as etree
+import re
+
+
+class AdmonitionExtension(Extension):
+    """ Admonition extension for Python-Markdown. """
+
+    def extendMarkdown(self, md):
+        """ Add Admonition to Markdown instance. """
+        md.registerExtension(self)
+
+        md.parser.blockprocessors.register(AdmonitionProcessor(md.parser), 'admonition', 105)
+
+
+class AdmonitionProcessor(BlockProcessor):
+
+    CLASSNAME = 'admonition'
+    CLASSNAME_TITLE = 'admonition-title'
+    RE = re.compile(r'(?:^|\n)!!! ?([\w\-]+(?: +[\w\-]+)*)(?: +"(.*?)")? *(?:\n|$)')
+    RE_SPACES = re.compile('  +')
+
+    def __init__(self, parser):
+        """Initialization."""
+
+        super().__init__(parser)
+
+        self.current_sibling = None
+        self.content_indention = 0
+
+    def parse_content(self, parent, block):
+        """Get sibling admonition.
+
+        Retrieve the appropriate sibling element. This can get tricky when
+        dealing with lists.
+
+        """
+
+        old_block = block
+        the_rest = ''
+
+        # We already acquired the block via test
+        if self.current_sibling is not None:
+            sibling = self.current_sibling
+            block, the_rest = self.detab(block, self.content_indent)
+            self.current_sibling = None
+            self.content_indent = 0
+            return sibling, block, the_rest
+
+        sibling = self.lastChild(parent)
+
+        if sibling is None or sibling.tag != 'div' or sibling.get('class', '').find(self.CLASSNAME) == -1:
+            sibling = None
+        else:
+            # If the last child is a list and the content is sufficiently indented
+            # to be under it, then the content's sibling is in the list.
+            last_child = self.lastChild(sibling)
+            indent = 0
+            while last_child is not None:
+                if (
+                    sibling is not None and block.startswith(' ' * self.tab_length * 2) and
+                    last_child is not None and last_child.tag in ('ul', 'ol', 'dl')
+                ):
+
+                    # The expectation is that we'll find an `<li>` or `<dt>`.
+                    # We should get its last child as well.
+                    sibling = self.lastChild(last_child)
+                    last_child = self.lastChild(sibling) if sibling is not None else None
+
+                    # Context has been lost at this point, so we must adjust the
+                    # text's indentation level so it will be evaluated correctly
+                    # under the list.
+                    block = block[self.tab_length:]
+                    indent += self.tab_length
+                else:
+                    last_child = None
+
+            if not block.startswith(' ' * self.tab_length):
+                sibling = None
+
+            if sibling is not None:
+                indent += self.tab_length
+                block, the_rest = self.detab(old_block, indent)
+                self.current_sibling = sibling
+                self.content_indent = indent
+
+        return sibling, block, the_rest
+
+    def test(self, parent, block):
+
+        if self.RE.search(block):
+            return True
+        else:
+            return self.parse_content(parent, block)[0] is not None
+
+    def run(self, parent, blocks):
+        block = blocks.pop(0)
+        m = self.RE.search(block)
+
+        if m:
+            if m.start() > 0:
+                self.parser.parseBlocks(parent, [block[:m.start()]])
+            block = block[m.end():]  # removes the first line
+            block, theRest = self.detab(block)
+        else:
+            sibling, block, theRest = self.parse_content(parent, block)
+
+        if m:
+            klass, title = self.get_class_and_title(m)
+            div = etree.SubElement(parent, 'div')
+            div.set('class', '{} {}'.format(self.CLASSNAME, klass))
+            if title:
+                p = etree.SubElement(div, 'p')
+                p.text = title
+                p.set('class', self.CLASSNAME_TITLE)
+        else:
+            # Sibling is a list item, but we need to wrap it's content should be wrapped in <p>
+            if sibling.tag in ('li', 'dd') and sibling.text:
+                text = sibling.text
+                sibling.text = ''
+                p = etree.SubElement(sibling, 'p')
+                p.text = text
+
+            div = sibling
+
+        self.parser.parseChunk(div, block)
+
+        if theRest:
+            # This block contained unindented line(s) after the first indented
+            # line. Insert these lines as the first block of the master blocks
+            # list for future processing.
+            blocks.insert(0, theRest)
+
+    def get_class_and_title(self, match):
+        klass, title = match.group(1).lower(), match.group(2)
+        klass = self.RE_SPACES.sub(' ', klass)
+        if title is None:
+            # no title was provided, use the capitalized class name as title
+            # e.g.: `!!! note` will render
+            # `<p class="admonition-title">Note</p>`
+            title = klass.split(' ', 1)[0].capitalize()
+        elif title == '':
+            # an explicit blank title should not be rendered
+            # e.g.: `!!! warning ""` will *not* render `p` with a title
+            title = None
+        return klass, title
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return AdmonitionExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/attr_list.py

@@ -0,0 +1,179 @@
+# 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://Python-Markdown.github.io/extensions/attr_list
+# for documentation.
+
+# Original code Copyright 2011 [Waylan Limberg](http://achinghead.com/).
+
+# All changes Copyright 2011-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+ Adds attribute list syntax. Inspired by
+[Maruku](http://maruku.rubyforge.org/proposal.html#attribute_lists)'s
+feature of the same name.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/attr_list)
+for details.
+"""
+
+from __future__ import annotations
+from typing import TYPE_CHECKING
+
+from . import Extension
+from ..treeprocessors import Treeprocessor
+import re
+
+if TYPE_CHECKING:  # pragma: no cover
+    from xml.etree.ElementTree import Element
+
+
+def _handle_double_quote(s, t):
+    k, v = t.split('=', 1)
+    return k, v.strip('"')
+
+
+def _handle_single_quote(s, t):
+    k, v = t.split('=', 1)
+    return k, v.strip("'")
+
+
+def _handle_key_value(s, t):
+    return t.split('=', 1)
+
+
+def _handle_word(s, t):
+    if t.startswith('.'):
+        return '.', t[1:]
+    if t.startswith('#'):
+        return 'id', t[1:]
+    return t, t
+
+
+_scanner = re.Scanner([
+    (r'[^ =]+=".*?"', _handle_double_quote),
+    (r"[^ =]+='.*?'", _handle_single_quote),
+    (r'[^ =]+=[^ =]+', _handle_key_value),
+    (r'[^ =]+', _handle_word),
+    (r' ', None)
+])
+
+
+def get_attrs(str: str) -> list[tuple[str, str]]:
+    """ Parse attribute list and return a list of attribute tuples. """
+    return _scanner.scan(str)[0]
+
+
+def isheader(elem: Element) -> bool:
+    return elem.tag in ['h1', 'h2', 'h3', 'h4', 'h5', 'h6']
+
+
+class AttrListTreeprocessor(Treeprocessor):
+
+    BASE_RE = r'\{\:?[ ]*([^\}\n ][^\}\n]*)[ ]*\}'
+    HEADER_RE = re.compile(r'[ ]+{}[ ]*$'.format(BASE_RE))
+    BLOCK_RE = re.compile(r'\n[ ]*{}[ ]*$'.format(BASE_RE))
+    INLINE_RE = re.compile(r'^{}'.format(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: Element):
+        for elem in doc.iter():
+            if self.md.is_block_level(elem.tag):
+                # Block level: check for `attrs` on last line of text
+                RE = self.BLOCK_RE
+                if isheader(elem) or elem.tag in ['dt', 'td', 'th']:
+                    # header, def-term, or table cell: check for attributes at end of element
+                    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 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: Element, attrs: str) -> None:
+        """ 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', '{} {}'.format(cls, v))
+                else:
+                    elem.set('class', v)
+            else:
+                # assign attribute `k` with `v`
+                elem.set(self.sanitize_name(k), v)
+
+    def sanitize_name(self, name: str) -> str:
+        """
+        Sanitize name as 'an XML Name, minus the ":"'.
+        See https://www.w3.org/TR/REC-xml-names/#NT-NCName
+        """
+        return self.NAME_RE.sub('_', name)
+
+
+class AttrListExtension(Extension):
+    """ Attribute List extension for Python-Markdown """
+    def extendMarkdown(self, md):
+        md.treeprocessors.register(AttrListTreeprocessor(md), 'attr_list', 8)
+        md.registerExtension(self)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return AttrListExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/codehilite.py

@@ -0,0 +1,338 @@
+# CodeHilite Extension for Python-Markdown
+# ========================================
+
+# Adds code/syntax highlighting to standard Python-Markdown code blocks.
+
+# See https://Python-Markdown.github.io/extensions/code_hilite
+# for documentation.
+
+# Original code Copyright 2006-2008 [Waylan Limberg](http://achinghead.com/).
+
+# All changes Copyright 2008-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+Adds code/syntax highlighting to standard Python-Markdown code blocks.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/code_hilite)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..treeprocessors import Treeprocessor
+from ..util import parseBoolValue
+
+try:  # pragma: no cover
+    from pygments import highlight
+    from pygments.lexers import get_lexer_by_name, guess_lexer
+    from pygments.formatters import get_formatter_by_name
+    from pygments.util import ClassNotFound
+    pygments = True
+except ImportError:  # pragma: no cover
+    pygments = False
+
+
+def parse_hl_lines(expr: str) -> list[int]:
+    """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 integers, the line numbers to emphasize.
+    """
+    if not expr:
+        return []
+
+    try:
+        return list(map(int, expr.split()))
+    except ValueError:  # pragma: no cover
+        return []
+
+
+# ------------------ The Main CodeHilite Class ----------------------
+class CodeHilite:
+    """
+    Determine language of source code, and pass it on to the Pygments highlighter.
+
+    Usage:
+
+    ```python
+    code = CodeHilite(src=some_code, lang='python')
+    html = code.hilite()
+    ```
+
+    Arguments:
+        src: Source string or any object with a `.readline` attribute.
+
+    Keyword arguments:
+        lang (str): String name of Pygments lexer to use for highlighting. Default: `None`.
+        guess_lang (bool): Auto-detect which lexer to use.
+            Ignored if `lang` is set to a valid value. Default: `True`.
+        use_pygments (bool): Pass code to Pygments for code highlighting. If `False`, the code is
+            instead wrapped for highlighting by a JavaScript library. Default: `True`.
+        pygments_formatter (str): The name of a Pygments formatter or a formatter class used for
+            highlighting the code blocks. Default: `html`.
+        linenums (bool): An alias to Pygments `linenos` formatter option. Default: `None`.
+        css_class (str): An alias to Pygments `cssclass` formatter option. Default: 'codehilite'.
+        lang_prefix (str): Prefix prepended to the language. Default: "language-".
+
+    Other Options:
+
+    Any other options are accepted and passed on to the lexer and formatter. Therefore,
+    valid options include any options which are accepted by the `html` formatter or
+    whichever lexer the code's language uses. Note that most lexers do not have any
+    options. However, a few have very useful options, such as PHP's `startinline` option.
+    Any invalid options are ignored without error.
+
+    * **Formatter options**: <https://pygments.org/docs/formatters/#HtmlFormatter>
+    * **Lexer Options**: <https://pygments.org/docs/lexers/>
+
+    Additionally, when Pygments is enabled, the code's language is passed to the
+    formatter as an extra option `lang_str`, whose value being `{lang_prefix}{lang}`.
+    This option has no effect to the Pygments' builtin formatters.
+
+    Advanced Usage:
+
+    ```python
+    code = CodeHilite(
+        src = some_code,
+        lang = 'php',
+        startinline = True,      # Lexer option. Snippet does not start with `<?php`.
+        linenostart = 42,        # Formatter option. Snippet starts on line 42.
+        hl_lines = [45, 49, 50], # Formatter option. Highlight lines 45, 49, and 50.
+        linenos = 'inline'       # Formatter option. Avoid alignment problems.
+    )
+    html = code.hilite()
+    ```
+
+    """
+
+    def __init__(self, src: str, **options):
+        self.src = src
+        self.lang = options.pop('lang', None)
+        self.guess_lang = options.pop('guess_lang', True)
+        self.use_pygments = options.pop('use_pygments', True)
+        self.lang_prefix = options.pop('lang_prefix', 'language-')
+        self.pygments_formatter = options.pop('pygments_formatter', 'html')
+
+        if 'linenos' not in options:
+            options['linenos'] = options.pop('linenums', None)
+        if 'cssclass' not in options:
+            options['cssclass'] = options.pop('css_class', 'codehilite')
+        if 'wrapcode' not in options:
+            # Override Pygments default
+            options['wrapcode'] = True
+        # Disallow use of `full` option
+        options['full'] = False
+
+        self.options = options
+
+    def hilite(self, shebang=True) -> str:
+        """
+        Pass code to the [Pygments](https://pygments.org/) highlighter 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 and shebang:
+            self._parseHeader()
+
+        if pygments and self.use_pygments:
+            try:
+                lexer = get_lexer_by_name(self.lang, **self.options)
+            except ValueError:
+                try:
+                    if self.guess_lang:
+                        lexer = guess_lexer(self.src, **self.options)
+                    else:
+                        lexer = get_lexer_by_name('text', **self.options)
+                except ValueError:  # pragma: no cover
+                    lexer = get_lexer_by_name('text', **self.options)
+            if not self.lang:
+                # Use the guessed lexer's language instead
+                self.lang = lexer.aliases[0]
+            lang_str = f'{self.lang_prefix}{self.lang}'
+            if isinstance(self.pygments_formatter, str):
+                try:
+                    formatter = get_formatter_by_name(self.pygments_formatter, **self.options)
+                except ClassNotFound:
+                    formatter = get_formatter_by_name('html', **self.options)
+            else:
+                formatter = self.pygments_formatter(lang_str=lang_str, **self.options)
+            return highlight(self.src, lexer, formatter)
+        else:
+            # just escape and build markup usable by JavaScript highlighting libraries
+            txt = self.src.replace('&', '&amp;')
+            txt = txt.replace('<', '&lt;')
+            txt = txt.replace('>', '&gt;')
+            txt = txt.replace('"', '&quot;')
+            classes = []
+            if self.lang:
+                classes.append('{}{}'.format(self.lang_prefix, self.lang))
+            if self.options['linenos']:
+                classes.append('linenums')
+            class_str = ''
+            if classes:
+                class_str = ' class="{}"'.format(' '.join(classes))
+            return '<pre class="{}"><code{}>{}\n</code></pre>\n'.format(
+                self.options['cssclass'],
+                class_str,
+                txt
+            )
+
+    def _parseHeader(self):
+        """
+        Determines language of a code block from shebang line and whether the
+        said line should be removed or left in place. If the shebang 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 identification 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:  # pragma: no cover
+                self.lang = None
+            if m.group('path'):
+                # path exists - restore first line
+                lines.insert(0, fl)
+            if self.options['linenos'] is None and m.group('shebang'):
+                # Overridable and Shebang exists - use line numbers
+                self.options['linenos'] = True
+
+            self.options['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):
+    """ Highlight source code in code blocks. """
+
+    def code_unescape(self, text):
+        """Unescape code."""
+        text = text.replace("&lt;", "<")
+        text = text.replace("&gt;", ">")
+        # Escaped '&' should be replaced at the end to avoid
+        # conflicting with < and >.
+        text = text.replace("&amp;", "&")
+        return text
+
+    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':
+                local_config = self.config.copy()
+                code = CodeHilite(
+                    self.code_unescape(block[0].text),
+                    tab_length=self.md.tab_length,
+                    style=local_config.pop('pygments_style', 'default'),
+                    **local_config
+                )
+                placeholder = self.md.htmlStash.store(code.hilite())
+                # Clear code block 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 highlighting to markdown code blocks. """
+
+    def __init__(self, **kwargs):
+        # define default configs
+        self.config = {
+            'linenums': [
+                None, "Use lines numbers. True|table|inline=yes, False=no, None=auto. Default: `None`."
+            ],
+            '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, 'Highlight code blocks with pygments. Disable if using a JavaScript library. Default: `True`.'
+            ],
+            'lang_prefix': [
+                'language-', 'Prefix prepended to the language when `use_pygments` is false. Default: `language-`.'
+            ],
+            'pygments_formatter': [
+                'html', 'Use a specific formatter for Pygments highlighting. Default: `html`.'
+            ],
+        }
+        """ Default configuration options. """
+
+        for key, value in kwargs.items():
+            if key in self.config:
+                self.setConfig(key, value)
+            else:
+                # manually set unknown keywords.
+                if isinstance(value, str):
+                    try:
+                        # Attempt to parse `str` as a boolean value
+                        value = parseBoolValue(value, preserve_none=True)
+                    except ValueError:
+                        pass  # Assume it's not a boolean value. Use as-is.
+                self.config[key] = [value, '']
+
+    def extendMarkdown(self, md):
+        """ Add `HilitePostprocessor` to Markdown instance. """
+        hiliter = HiliteTreeprocessor(md)
+        hiliter.config = self.getConfigs()
+        md.treeprocessors.register(hiliter, 'hilite', 30)
+
+        md.registerExtension(self)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return CodeHiliteExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/def_list.py

@@ -0,0 +1,119 @@
+# Definition List Extension for Python-Markdown
+# =============================================
+
+# Adds parsing of Definition Lists to Python-Markdown.
+
+# See https://Python-Markdown.github.io/extensions/definition_lists
+# for documentation.
+
+# Original code Copyright 2008 [Waylan Limberg](http://achinghead.com)
+
+# All changes Copyright 2008-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+Adds parsing of Definition Lists to Python-Markdown.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/definition_lists)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..blockprocessors import BlockProcessor, ListIndentProcessor
+import xml.etree.ElementTree as etree
+import re
+
+
+class DefListProcessor(BlockProcessor):
+    """ Process Definition Lists. """
+
+    RE = re.compile(r'(^|\n)[ ]{0,3}:[ ]{1,3}(.*?)(\n|$)')
+    NO_INDENT_RE = re.compile(r'^[ ]{0,3}[^ :]')
+
+    def test(self, parent, block):
+        return bool(self.RE.search(block))
+
+    def run(self, parent, blocks):
+
+        raw_block = blocks.pop(0)
+        m = self.RE.search(raw_block)
+        terms = [term.strip() for term in
+                 raw_block[:m.start()].split('\n') if term.strip()]
+        block = raw_block[m.end():]
+        no_indent = self.NO_INDENT_RE.match(block)
+        if no_indent:
+            d, theRest = (block, None)
+        else:
+            d, theRest = self.detab(block)
+        if d:
+            d = '{}\n{}'.format(m.group(2), d)
+        else:
+            d = m.group(2)
+        sibling = self.lastChild(parent)
+        if not terms and sibling is None:
+            # This is not a definition item. Most likely a paragraph that
+            # starts with a colon at the beginning of a document or list.
+            blocks.insert(0, raw_block)
+            return False
+        if not terms and sibling.tag == 'p':
+            # The previous paragraph contains the terms
+            state = 'looselist'
+            terms = sibling.text.split('\n')
+            parent.remove(sibling)
+            # Acquire new sibling
+            sibling = self.lastChild(parent)
+        else:
+            state = 'list'
+
+        if sibling is not None and sibling.tag == 'dl':
+            # This is another item on an existing list
+            dl = sibling
+            if not terms and len(dl) and dl[-1].tag == 'dd' and len(dl[-1]):
+                state = 'looselist'
+        else:
+            # This is a new list
+            dl = etree.SubElement(parent, 'dl')
+        # Add terms
+        for term in terms:
+            dt = etree.SubElement(dl, 'dt')
+            dt.text = term
+        # Add definition
+        self.parser.state.set(state)
+        dd = etree.SubElement(dl, 'dd')
+        self.parser.parseBlocks(dd, [d])
+        self.parser.state.reset()
+
+        if theRest:
+            blocks.insert(0, theRest)
+
+
+class DefListIndentProcessor(ListIndentProcessor):
+    """ Process indented children of definition list items. """
+
+    # Definition lists need to be aware of all list types
+    ITEM_TYPES = ['dd', 'li']
+    """ Include `dd` in list item types. """
+    LIST_TYPES = ['dl', 'ol', 'ul']
+    """ Include `dl` is list types. """
+
+    def create_item(self, parent, block):
+        """ Create a new `dd` or `li` (depending on parent) and parse the block with it as the parent. """
+
+        dd = etree.SubElement(parent, 'dd')
+        self.parser.parseBlocks(dd, [block])
+
+
+class DefListExtension(Extension):
+    """ Add definition lists to Markdown. """
+
+    def extendMarkdown(self, md):
+        """ Add an instance of `DefListProcessor` to `BlockParser`. """
+        md.parser.blockprocessors.register(DefListIndentProcessor(md.parser), 'defindent', 85)
+        md.parser.blockprocessors.register(DefListProcessor(md.parser), 'deflist', 25)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return DefListExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/extra.py

@@ -0,0 +1,66 @@
+# Python-Markdown Extra Extension
+# ===============================
+
+# A compilation of various Python-Markdown extensions that imitates
+# [PHP Markdown Extra](http://michelf.com/projects/php-markdown/extra/).
+
+# See https://Python-Markdown.github.io/extensions/extra
+# for documentation.
+
+# Copyright The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+A compilation of various Python-Markdown extensions that imitates
+[PHP Markdown Extra](http://michelf.com/projects/php-markdown/extra/).
+
+Note that each of the individual extensions still need to be available
+on your `PYTHONPATH`. This extension simply wraps them all up as a
+convenience so that only one extension needs to be listed when
+initiating Markdown. See the documentation for each individual
+extension for specifics about that extension.
+
+There may be additional extensions that are distributed with
+Python-Markdown that are not included here in Extra. Those extensions
+are not part of PHP Markdown Extra, and therefore, not part of
+Python-Markdown Extra. If you really would like Extra to include
+additional extensions, we suggest creating your own clone of Extra
+under a different name. You could also edit the `extensions` global
+variable defined below, but be aware that such changes may be lost
+when you upgrade to any future version of Python-Markdown.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/extra)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+
+extensions = [
+    'fenced_code',
+    'footnotes',
+    'attr_list',
+    'def_list',
+    'tables',
+    'abbr',
+    'md_in_html'
+]
+""" The list of included extensions. """
+
+
+class ExtraExtension(Extension):
+    """ Add various extensions to Markdown class."""
+
+    def __init__(self, **kwargs):
+        """ `config` is a dumb holder which gets passed to the actual extension later. """
+        self.config = kwargs
+
+    def extendMarkdown(self, md):
+        """ Register extension instances. """
+        md.registerExtensions(extensions, self.config)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return ExtraExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/fenced_code.py

@@ -0,0 +1,182 @@
+# Fenced Code Extension for Python Markdown
+# =========================================
+
+# This extension adds Fenced Code Blocks to Python-Markdown.
+
+# See https://Python-Markdown.github.io/extensions/fenced_code_blocks
+# for documentation.
+
+# Original code Copyright 2007-2008 [Waylan Limberg](http://achinghead.com/).
+
+# All changes Copyright 2008-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+This extension adds Fenced Code Blocks to Python-Markdown.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/fenced_code_blocks)
+for details.
+"""
+
+from __future__ import annotations
+
+from textwrap import dedent
+from . import Extension
+from ..preprocessors import Preprocessor
+from .codehilite import CodeHilite, CodeHiliteExtension, parse_hl_lines
+from .attr_list import get_attrs, AttrListExtension
+from ..util import parseBoolValue
+from ..serializers import _escape_attrib_html
+import re
+
+
+class FencedCodeExtension(Extension):
+    def __init__(self, **kwargs):
+        self.config = {
+            'lang_prefix': ['language-', 'Prefix prepended to the language. Default: "language-"']
+        }
+        """ Default configuration options. """
+        super().__init__(**kwargs)
+
+    def extendMarkdown(self, md):
+        """ Add `FencedBlockPreprocessor` to the Markdown instance. """
+        md.registerExtension(self)
+
+        md.preprocessors.register(FencedBlockPreprocessor(md, self.getConfigs()), 'fenced_code_block', 25)
+
+
+class FencedBlockPreprocessor(Preprocessor):
+    """ Find and extract fenced code blocks. """
+
+    FENCED_BLOCK_RE = re.compile(
+        dedent(r'''
+            (?P<fence>^(?:~{3,}|`{3,}))[ ]*                          # opening fence
+            ((\{(?P<attrs>[^\}\n]*)\})|                              # (optional {attrs} or
+            (\.?(?P<lang>[\w#.+-]*)[ ]*)?                            # optional (.)lang
+            (hl_lines=(?P<quot>"|')(?P<hl_lines>.*?)(?P=quot)[ ]*)?) # optional hl_lines)
+            \n                                                       # newline (end of opening fence)
+            (?P<code>.*?)(?<=\n)                                     # the code block
+            (?P=fence)[ ]*$                                          # closing fence
+        '''),
+        re.MULTILINE | re.DOTALL | re.VERBOSE
+    )
+
+    def __init__(self, md, config):
+        super().__init__(md)
+        self.config = config
+        self.checked_for_deps = False
+        self.codehilite_conf = {}
+        self.use_attr_list = False
+        # List of options to convert to boolean values
+        self.bool_options = [
+            'linenums',
+            'guess_lang',
+            'noclasses',
+            'use_pygments'
+        ]
+
+    def run(self, lines):
+        """ Match and store Fenced Code Blocks in the `HtmlStash`. """
+
+        # Check for dependent extensions
+        if not self.checked_for_deps:
+            for ext in self.md.registeredExtensions:
+                if isinstance(ext, CodeHiliteExtension):
+                    self.codehilite_conf = ext.getConfigs()
+                if isinstance(ext, AttrListExtension):
+                    self.use_attr_list = True
+
+            self.checked_for_deps = True
+
+        text = "\n".join(lines)
+        while 1:
+            m = self.FENCED_BLOCK_RE.search(text)
+            if m:
+                lang, id, classes, config = None, '', [], {}
+                if m.group('attrs'):
+                    id, classes, config = self.handle_attrs(get_attrs(m.group('attrs')))
+                    if len(classes):
+                        lang = classes.pop(0)
+                else:
+                    if m.group('lang'):
+                        lang = m.group('lang')
+                    if m.group('hl_lines'):
+                        # Support `hl_lines` outside of `attrs` for backward-compatibility
+                        config['hl_lines'] = parse_hl_lines(m.group('hl_lines'))
+
+                # If `config` is not empty, then the `codehighlite` extension
+                # is enabled, so we call it to highlight the code
+                if self.codehilite_conf and self.codehilite_conf['use_pygments'] and config.get('use_pygments', True):
+                    local_config = self.codehilite_conf.copy()
+                    local_config.update(config)
+                    # Combine classes with `cssclass`. Ensure `cssclass` is at end
+                    # as Pygments appends a suffix under certain circumstances.
+                    # Ignore ID as Pygments does not offer an option to set it.
+                    if classes:
+                        local_config['css_class'] = '{} {}'.format(
+                            ' '.join(classes),
+                            local_config['css_class']
+                        )
+                    highliter = CodeHilite(
+                        m.group('code'),
+                        lang=lang,
+                        style=local_config.pop('pygments_style', 'default'),
+                        **local_config
+                    )
+
+                    code = highliter.hilite(shebang=False)
+                else:
+                    id_attr = lang_attr = class_attr = kv_pairs = ''
+                    if lang:
+                        prefix = self.config.get('lang_prefix', 'language-')
+                        lang_attr = f' class="{prefix}{_escape_attrib_html(lang)}"'
+                    if classes:
+                        class_attr = f' class="{_escape_attrib_html(" ".join(classes))}"'
+                    if id:
+                        id_attr = f' id="{_escape_attrib_html(id)}"'
+                    if self.use_attr_list and config and not config.get('use_pygments', False):
+                        # Only assign key/value pairs to code element if `attr_list` extension is enabled, key/value
+                        # pairs were defined on the code block, and the `use_pygments` key was not set to `True`. The
+                        # `use_pygments` key could be either set to `False` or not defined. It is omitted from output.
+                        kv_pairs = ''.join(
+                            f' {k}="{_escape_attrib_html(v)}"' for k, v in config.items() if k != 'use_pygments'
+                        )
+                    code = self._escape(m.group('code'))
+                    code = f'<pre{id_attr}{class_attr}><code{lang_attr}{kv_pairs}>{code}</code></pre>'
+
+                placeholder = self.md.htmlStash.store(code)
+                text = f'{text[:m.start()]}\n{placeholder}\n{text[m.end():]}'
+            else:
+                break
+        return text.split("\n")
+
+    def handle_attrs(self, attrs):
+        """ Return tuple: `(id, [list, of, classes], {configs})` """
+        id = ''
+        classes = []
+        configs = {}
+        for k, v in attrs:
+            if k == 'id':
+                id = v
+            elif k == '.':
+                classes.append(v)
+            elif k == 'hl_lines':
+                configs[k] = parse_hl_lines(v)
+            elif k in self.bool_options:
+                configs[k] = parseBoolValue(v, fail_on_errors=False, preserve_none=True)
+            else:
+                configs[k] = v
+        return id, classes, configs
+
+    def _escape(self, txt):
+        """ basic html escaping """
+        txt = txt.replace('&', '&amp;')
+        txt = txt.replace('<', '&lt;')
+        txt = txt.replace('>', '&gt;')
+        txt = txt.replace('"', '&quot;')
+        return txt
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return FencedCodeExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/footnotes.py

@@ -0,0 +1,416 @@
+# Footnotes Extension for Python-Markdown
+# =======================================
+
+# Adds footnote handling to Python-Markdown.
+
+# See https://Python-Markdown.github.io/extensions/footnotes
+# for documentation.
+
+# Copyright The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+Adds footnote handling to Python-Markdown.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/footnotes)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..blockprocessors import BlockProcessor
+from ..inlinepatterns import InlineProcessor
+from ..treeprocessors import Treeprocessor
+from ..postprocessors import Postprocessor
+from .. import util
+from collections import OrderedDict
+import re
+import copy
+import xml.etree.ElementTree as etree
+
+FN_BACKLINK_TEXT = util.STX + "zz1337820767766393qq" + util.ETX
+NBSP_PLACEHOLDER = util.STX + "qq3936677670287331zz" + util.ETX
+RE_REF_ID = re.compile(r'(fnref)(\d+)')
+
+
+class FootnoteExtension(Extension):
+    """ Footnote Extension. """
+
+    def __init__(self, **kwargs):
+        """ Setup configs. """
+
+        self.config = {
+            'PLACE_MARKER': [
+                '///Footnotes Go Here///', 'The text string that marks where the footnotes go'
+            ],
+            'UNIQUE_IDS': [
+                False, 'Avoid name collisions across multiple calls to `reset()`.'
+            ],
+            'BACKLINK_TEXT': [
+                '↩', "The text string that links from the footnote to the reader's place."
+            ],
+            'SUPERSCRIPT_TEXT': [
+                '{}', "The text string that links from the reader's place to the footnote."
+            ],
+            'BACKLINK_TITLE': [
+                'Jump back to footnote %d in the text',
+                'The text string used for the title HTML attribute of the backlink. '
+                '%d will be replaced by the footnote number.'
+            ],
+            'SEPARATOR': [
+                ':', 'Footnote separator.'
+            ]
+        }
+        """ Default configuration options. """
+        super().__init__(**kwargs)
+
+        # In multiple invocations, emit links that don't get tangled.
+        self.unique_prefix = 0
+        self.found_refs = {}
+        self.used_refs = set()
+
+        self.reset()
+
+    def extendMarkdown(self, md):
+        """ Add pieces to Markdown. """
+        md.registerExtension(self)
+        self.parser = md.parser
+        self.md = md
+        # Insert a `blockprocessor` before `ReferencePreprocessor`
+        md.parser.blockprocessors.register(FootnoteBlockProcessor(self), 'footnote', 17)
+
+        # Insert an inline pattern before `ImageReferencePattern`
+        FOOTNOTE_RE = r'\[\^([^\]]*)\]'  # blah blah [^1] blah
+        md.inlinePatterns.register(FootnoteInlineProcessor(FOOTNOTE_RE, self), 'footnote', 175)
+        # Insert a tree-processor that would actually add the footnote div
+        # This must be before all other tree-processors (i.e., `inline` and
+        # `codehilite`) so they can run on the the contents of the div.
+        md.treeprocessors.register(FootnoteTreeprocessor(self), 'footnote', 50)
+
+        # Insert a tree-processor that will run after inline is done.
+        # In this tree-processor we want to check our duplicate footnote tracker
+        # And add additional `backrefs` to the footnote pointing back to the
+        # duplicated references.
+        md.treeprocessors.register(FootnotePostTreeprocessor(self), 'footnote-duplicate', 15)
+
+        # Insert a postprocessor after amp_substitute processor
+        md.postprocessors.register(FootnotePostprocessor(self), 'footnote', 25)
+
+    def reset(self) -> None:
+        """ Clear footnotes on reset, and prepare for distinct document. """
+        self.footnotes: OrderedDict[str, str] = OrderedDict()
+        self.unique_prefix += 1
+        self.found_refs = {}
+        self.used_refs = set()
+
+    def unique_ref(self, reference, found: bool = False):
+        """ Get a unique reference if there are duplicates. """
+        if not found:
+            return reference
+
+        original_ref = reference
+        while reference in self.used_refs:
+            ref, rest = reference.split(self.get_separator(), 1)
+            m = RE_REF_ID.match(ref)
+            if m:
+                reference = '%s%d%s%s' % (m.group(1), int(m.group(2))+1, self.get_separator(), rest)
+            else:
+                reference = '%s%d%s%s' % (ref, 2, self.get_separator(), rest)
+
+        self.used_refs.add(reference)
+        if original_ref in self.found_refs:
+            self.found_refs[original_ref] += 1
+        else:
+            self.found_refs[original_ref] = 1
+        return reference
+
+    def findFootnotesPlaceholder(self, root):
+        """ Return ElementTree Element that contains Footnote placeholder. """
+        def finder(element):
+            for child in element:
+                if child.text:
+                    if child.text.find(self.getConfig("PLACE_MARKER")) > -1:
+                        return child, element, True
+                if child.tail:
+                    if child.tail.find(self.getConfig("PLACE_MARKER")) > -1:
+                        return child, element, False
+                child_res = finder(child)
+                if child_res is not None:
+                    return child_res
+            return None
+
+        res = finder(root)
+        return res
+
+    def setFootnote(self, id, text) -> None:
+        """ Store a footnote for later retrieval. """
+        self.footnotes[id] = text
+
+    def get_separator(self):
+        """ Get the footnote separator. """
+        return self.getConfig("SEPARATOR")
+
+    def makeFootnoteId(self, id):
+        """ Return footnote link id. """
+        if self.getConfig("UNIQUE_IDS"):
+            return 'fn%s%d-%s' % (self.get_separator(), self.unique_prefix, id)
+        else:
+            return 'fn{}{}'.format(self.get_separator(), id)
+
+    def makeFootnoteRefId(self, id, found: bool = False):
+        """ Return footnote back-link id. """
+        if self.getConfig("UNIQUE_IDS"):
+            return self.unique_ref('fnref%s%d-%s' % (self.get_separator(), self.unique_prefix, id), found)
+        else:
+            return self.unique_ref('fnref{}{}'.format(self.get_separator(), id), found)
+
+    def makeFootnotesDiv(self, root):
+        """ Return `div` of footnotes as `etree` Element. """
+
+        if not list(self.footnotes.keys()):
+            return None
+
+        div = etree.Element("div")
+        div.set('class', 'footnote')
+        etree.SubElement(div, "hr")
+        ol = etree.SubElement(div, "ol")
+        surrogate_parent = etree.Element("div")
+
+        # Backward compatibility with old '%d' placeholder
+        backlink_title = self.getConfig("BACKLINK_TITLE").replace("%d", "{}")
+
+        for index, id in enumerate(self.footnotes.keys(), start=1):
+            li = etree.SubElement(ol, "li")
+            li.set("id", self.makeFootnoteId(id))
+            # Parse footnote with surrogate parent as `li` cannot be used.
+            # List block handlers have special logic to deal with `li`.
+            # When we are done parsing, we will copy everything over to `li`.
+            self.parser.parseChunk(surrogate_parent, self.footnotes[id])
+            for el in list(surrogate_parent):
+                li.append(el)
+                surrogate_parent.remove(el)
+            backlink = etree.Element("a")
+            backlink.set("href", "#" + self.makeFootnoteRefId(id))
+            backlink.set("class", "footnote-backref")
+            backlink.set(
+                "title",
+                backlink_title.format(index)
+            )
+            backlink.text = FN_BACKLINK_TEXT
+
+            if len(li):
+                node = li[-1]
+                if node.tag == "p":
+                    node.text = node.text + NBSP_PLACEHOLDER
+                    node.append(backlink)
+                else:
+                    p = etree.SubElement(li, "p")
+                    p.append(backlink)
+        return div
+
+
+class FootnoteBlockProcessor(BlockProcessor):
+    """ Find all footnote references and store for later use. """
+
+    RE = re.compile(r'^[ ]{0,3}\[\^([^\]]*)\]:[ ]*(.*)$', re.MULTILINE)
+
+    def __init__(self, footnotes):
+        super().__init__(footnotes.parser)
+        self.footnotes = footnotes
+
+    def test(self, parent, block):
+        return True
+
+    def run(self, parent, blocks):
+        """ Find, set, and remove footnote definitions. """
+        block = blocks.pop(0)
+        m = self.RE.search(block)
+        if m:
+            id = m.group(1)
+            fn_blocks = [m.group(2)]
+
+            # Handle rest of block
+            therest = block[m.end():].lstrip('\n')
+            m2 = self.RE.search(therest)
+            if m2:
+                # Another footnote exists in the rest of this block.
+                # Any content before match is continuation of this footnote, which may be lazily indented.
+                before = therest[:m2.start()].rstrip('\n')
+                fn_blocks[0] = '\n'.join([fn_blocks[0], self.detab(before)]).lstrip('\n')
+                # Add back to blocks everything from beginning of match forward for next iteration.
+                blocks.insert(0, therest[m2.start():])
+            else:
+                # All remaining lines of block are continuation of this footnote, which may be lazily indented.
+                fn_blocks[0] = '\n'.join([fn_blocks[0], self.detab(therest)]).strip('\n')
+
+                # Check for child elements in remaining blocks.
+                fn_blocks.extend(self.detectTabbed(blocks))
+
+            footnote = "\n\n".join(fn_blocks)
+            self.footnotes.setFootnote(id, footnote.rstrip())
+
+            if block[:m.start()].strip():
+                # Add any content before match back to blocks as separate block
+                blocks.insert(0, block[:m.start()].rstrip('\n'))
+            return True
+        # No match. Restore block.
+        blocks.insert(0, block)
+        return False
+
+    def detectTabbed(self, blocks) -> list[str]:
+        """ Find indented text and remove indent before further processing.
+
+        Returns:
+            A list of blocks with indentation removed.
+        """
+        fn_blocks = []
+        while blocks:
+            if blocks[0].startswith(' '*4):
+                block = blocks.pop(0)
+                # Check for new footnotes within this block and split at new footnote.
+                m = self.RE.search(block)
+                if m:
+                    # Another footnote exists in this block.
+                    # Any content before match is continuation of this footnote, which may be lazily indented.
+                    before = block[:m.start()].rstrip('\n')
+                    fn_blocks.append(self.detab(before))
+                    # Add back to blocks everything from beginning of match forward for next iteration.
+                    blocks.insert(0, block[m.start():])
+                    # End of this footnote.
+                    break
+                else:
+                    # Entire block is part of this footnote.
+                    fn_blocks.append(self.detab(block))
+            else:
+                # End of this footnote.
+                break
+        return fn_blocks
+
+    def detab(self, block):
+        """ Remove one level of indent from a block.
+
+        Preserve lazily indented blocks by only removing indent from indented lines.
+        """
+        lines = block.split('\n')
+        for i, line in enumerate(lines):
+            if line.startswith(' '*4):
+                lines[i] = line[4:]
+        return '\n'.join(lines)
+
+
+class FootnoteInlineProcessor(InlineProcessor):
+    """ `InlineProcessor` for footnote markers in a document's body text. """
+
+    def __init__(self, pattern, footnotes):
+        super().__init__(pattern)
+        self.footnotes = footnotes
+
+    def handleMatch(self, m, data):
+        id = m.group(1)
+        if id in self.footnotes.footnotes.keys():
+            sup = etree.Element("sup")
+            a = etree.SubElement(sup, "a")
+            sup.set('id', self.footnotes.makeFootnoteRefId(id, found=True))
+            a.set('href', '#' + self.footnotes.makeFootnoteId(id))
+            a.set('class', 'footnote-ref')
+            a.text = self.footnotes.getConfig("SUPERSCRIPT_TEXT").format(
+                list(self.footnotes.footnotes.keys()).index(id) + 1
+            )
+            return sup, m.start(0), m.end(0)
+        else:
+            return None, None, None
+
+
+class FootnotePostTreeprocessor(Treeprocessor):
+    """ Amend footnote div with duplicates. """
+
+    def __init__(self, footnotes):
+        self.footnotes = footnotes
+
+    def add_duplicates(self, li, duplicates) -> None:
+        """ Adjust current `li` and add the duplicates: `fnref2`, `fnref3`, etc. """
+        for link in li.iter('a'):
+            # Find the link that needs to be duplicated.
+            if link.attrib.get('class', '') == 'footnote-backref':
+                ref, rest = link.attrib['href'].split(self.footnotes.get_separator(), 1)
+                # Duplicate link the number of times we need to
+                # and point the to the appropriate references.
+                links = []
+                for index in range(2, duplicates + 1):
+                    sib_link = copy.deepcopy(link)
+                    sib_link.attrib['href'] = '%s%d%s%s' % (ref, index, self.footnotes.get_separator(), rest)
+                    links.append(sib_link)
+                    self.offset += 1
+                # Add all the new duplicate links.
+                el = list(li)[-1]
+                for link in links:
+                    el.append(link)
+                break
+
+    def get_num_duplicates(self, li):
+        """ Get the number of duplicate refs of the footnote. """
+        fn, rest = li.attrib.get('id', '').split(self.footnotes.get_separator(), 1)
+        link_id = '{}ref{}{}'.format(fn, self.footnotes.get_separator(), rest)
+        return self.footnotes.found_refs.get(link_id, 0)
+
+    def handle_duplicates(self, parent) -> None:
+        """ Find duplicate footnotes and format and add the duplicates. """
+        for li in list(parent):
+            # Check number of duplicates footnotes and insert
+            # additional links if needed.
+            count = self.get_num_duplicates(li)
+            if count > 1:
+                self.add_duplicates(li, count)
+
+    def run(self, root):
+        """ Crawl the footnote div and add missing duplicate footnotes. """
+        self.offset = 0
+        for div in root.iter('div'):
+            if div.attrib.get('class', '') == 'footnote':
+                # Footnotes should be under the first ordered list under
+                # the footnote div.  So once we find it, quit.
+                for ol in div.iter('ol'):
+                    self.handle_duplicates(ol)
+                    break
+
+
+class FootnoteTreeprocessor(Treeprocessor):
+    """ Build and append footnote div to end of document. """
+
+    def __init__(self, footnotes):
+        self.footnotes = footnotes
+
+    def run(self, root):
+        footnotesDiv = self.footnotes.makeFootnotesDiv(root)
+        if footnotesDiv is not None:
+            result = self.footnotes.findFootnotesPlaceholder(root)
+            if result:
+                child, parent, isText = result
+                ind = list(parent).index(child)
+                if isText:
+                    parent.remove(child)
+                    parent.insert(ind, footnotesDiv)
+                else:
+                    parent.insert(ind + 1, footnotesDiv)
+                    child.tail = None
+            else:
+                root.append(footnotesDiv)
+
+
+class FootnotePostprocessor(Postprocessor):
+    """ Replace placeholders with html entities. """
+    def __init__(self, footnotes):
+        self.footnotes = footnotes
+
+    def run(self, text):
+        text = text.replace(
+            FN_BACKLINK_TEXT, self.footnotes.getConfig("BACKLINK_TEXT")
+        )
+        return text.replace(NBSP_PLACEHOLDER, " ")
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    """ Return an instance of the `FootnoteExtension` """
+    return FootnoteExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/legacy_attrs.py

@@ -0,0 +1,67 @@
+# Python Markdown
+
+# A Python implementation of John Gruber's Markdown.
+
+# Documentation: https://python-markdown.github.io/
+# GitHub: https://github.com/Python-Markdown/markdown/
+# PyPI: https://pypi.org/project/Markdown/
+
+# Started by Manfred Stienstra (http://www.dwerg.net/).
+# Maintained for a few years by Yuri Takhteyev (http://www.freewisdom.org).
+# Currently maintained by Waylan Limberg (https://github.com/waylan),
+# Dmitry Shachnev (https://github.com/mitya57) and Isaac Muse (https://github.com/facelessuser).
+
+# Copyright 2007-2023 The Python Markdown Project (v. 1.7 and later)
+# Copyright 2004, 2005, 2006 Yuri Takhteyev (v. 0.2-1.6b)
+# Copyright 2004 Manfred Stienstra (the original version)
+
+# License: BSD (see LICENSE.md for details).
+
+"""
+An extension to Python Markdown which implements legacy attributes.
+
+Prior to Python-Markdown version 3.0, the Markdown class had an `enable_attributes`
+keyword which was on by default and provided for attributes to be defined for elements
+using the format `{@key=value}`. This extension is provided as a replacement for
+backward compatibility. New documents should be authored using `attr_lists`. However,
+numerous documents exist which have been using the old attribute format for many
+years. This extension can be used to continue to render those documents correctly.
+"""
+
+from __future__ import annotations
+
+import re
+from markdown.treeprocessors import Treeprocessor, isString
+from markdown.extensions import Extension
+
+
+ATTR_RE = re.compile(r'\{@([^\}]*)=([^\}]*)}')  # {@id=123}
+
+
+class LegacyAttrs(Treeprocessor):
+    def run(self, doc):
+        """Find and set values of attributes ({@key=value}). """
+        for el in doc.iter():
+            alt = el.get('alt', None)
+            if alt is not None:
+                el.set('alt', self.handleAttributes(el, alt))
+            if el.text and isString(el.text):
+                el.text = self.handleAttributes(el, el.text)
+            if el.tail and isString(el.tail):
+                el.tail = self.handleAttributes(el, el.tail)
+
+    def handleAttributes(self, el, txt):
+        """ Set attributes and return text without definitions. """
+        def attributeCallback(match):
+            el.set(match.group(1), match.group(2).replace('\n', ' '))
+        return ATTR_RE.sub(attributeCallback, txt)
+
+
+class LegacyAttrExtension(Extension):
+    def extendMarkdown(self, md):
+        """ Add `LegacyAttrs` to Markdown instance. """
+        md.treeprocessors.register(LegacyAttrs(md), 'legacyattrs', 15)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return LegacyAttrExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/legacy_em.py

@@ -0,0 +1,52 @@
+# Legacy Em Extension for Python-Markdown
+# =======================================
+
+# This extension provides legacy behavior for _connected_words_.
+
+# Copyright 2015-2018 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+This extension provides legacy behavior for _connected_words_.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..inlinepatterns import UnderscoreProcessor, EmStrongItem, EM_STRONG2_RE, STRONG_EM2_RE
+import re
+
+# _emphasis_
+EMPHASIS_RE = r'(_)([^_]+)\1'
+
+# __strong__
+STRONG_RE = r'(_{2})(.+?)\1'
+
+# __strong_em___
+STRONG_EM_RE = r'(_)\1(?!\1)([^_]+?)\1(?!\1)(.+?)\1{3}'
+
+
+class LegacyUnderscoreProcessor(UnderscoreProcessor):
+    """Emphasis processor for handling strong and em matches inside underscores."""
+
+    PATTERNS = [
+        EmStrongItem(re.compile(EM_STRONG2_RE, re.DOTALL | re.UNICODE), 'double', 'strong,em'),
+        EmStrongItem(re.compile(STRONG_EM2_RE, re.DOTALL | re.UNICODE), 'double', 'em,strong'),
+        EmStrongItem(re.compile(STRONG_EM_RE, re.DOTALL | re.UNICODE), 'double2', 'strong,em'),
+        EmStrongItem(re.compile(STRONG_RE, re.DOTALL | re.UNICODE), 'single', 'strong'),
+        EmStrongItem(re.compile(EMPHASIS_RE, re.DOTALL | re.UNICODE), 'single', 'em')
+    ]
+
+
+class LegacyEmExtension(Extension):
+    """ Add legacy_em extension to Markdown class."""
+
+    def extendMarkdown(self, md):
+        """ Modify inline patterns. """
+        md.inlinePatterns.register(LegacyUnderscoreProcessor(r'_'), 'em_strong2', 50)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    """ Return an instance of the `LegacyEmExtension` """
+    return LegacyEmExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/md_in_html.py

@@ -0,0 +1,372 @@
+# Python-Markdown Markdown in HTML Extension
+# ===============================
+
+# An implementation of [PHP Markdown Extra](http://michelf.com/projects/php-markdown/extra/)'s
+# parsing of Markdown syntax in raw HTML.
+
+# See https://Python-Markdown.github.io/extensions/raw_html
+# for documentation.
+
+# Copyright The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+An implementation of [PHP Markdown Extra](http://michelf.com/projects/php-markdown/extra/)'s
+parsing of Markdown syntax in raw HTML.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/raw_html)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..blockprocessors import BlockProcessor
+from ..preprocessors import Preprocessor
+from ..postprocessors import RawHtmlPostprocessor
+from .. import util
+from ..htmlparser import HTMLExtractor, blank_line_re
+import xml.etree.ElementTree as etree
+
+
+class HTMLExtractorExtra(HTMLExtractor):
+    """
+    Override `HTMLExtractor` and create `etree` `Elements` for any elements which should have content parsed as
+    Markdown.
+    """
+
+    def __init__(self, md, *args, **kwargs):
+        # All block-level tags.
+        self.block_level_tags = set(md.block_level_elements.copy())
+        # Block-level tags in which the content only gets span level parsing
+        self.span_tags = set(
+            ['address', 'dd', 'dt', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'legend', 'li', 'p', 'summary', 'td', 'th']
+        )
+        # Block-level tags which never get their content parsed.
+        self.raw_tags = set(['canvas', 'math', 'option', 'pre', 'script', 'style', 'textarea'])
+
+        super().__init__(md, *args, **kwargs)
+
+        # Block-level tags in which the content gets parsed as blocks
+        self.block_tags = set(self.block_level_tags) - (self.span_tags | self.raw_tags | self.empty_tags)
+        self.span_and_blocks_tags = self.block_tags | self.span_tags
+
+    def reset(self):
+        """Reset this instance.  Loses all unprocessed data."""
+        self.mdstack = []  # When markdown=1, stack contains a list of tags
+        self.treebuilder = etree.TreeBuilder()
+        self.mdstate = []  # one of 'block', 'span', 'off', or None
+        super().reset()
+
+    def close(self):
+        """Handle any buffered data."""
+        super().close()
+        # Handle any unclosed tags.
+        if self.mdstack:
+            # Close the outermost parent. `handle_endtag` will close all unclosed children.
+            self.handle_endtag(self.mdstack[0])
+
+    def get_element(self):
+        """ Return element from `treebuilder` and reset `treebuilder` for later use. """
+        element = self.treebuilder.close()
+        self.treebuilder = etree.TreeBuilder()
+        return element
+
+    def get_state(self, tag, attrs):
+        """ Return state from tag and `markdown` attribute. One of 'block', 'span', or 'off'. """
+        md_attr = attrs.get('markdown', '0')
+        if md_attr == 'markdown':
+            # `<tag markdown>` is the same as `<tag markdown='1'>`.
+            md_attr = '1'
+        parent_state = self.mdstate[-1] if self.mdstate else None
+        if parent_state == 'off' or (parent_state == 'span' and md_attr != '0'):
+            # Only use the parent state if it is more restrictive than the markdown attribute.
+            md_attr = parent_state
+        if ((md_attr == '1' and tag in self.block_tags) or
+                (md_attr == 'block' and tag in self.span_and_blocks_tags)):
+            return 'block'
+        elif ((md_attr == '1' and tag in self.span_tags) or
+              (md_attr == 'span' and tag in self.span_and_blocks_tags)):
+            return 'span'
+        elif tag in self.block_level_tags:
+            return 'off'
+        else:  # pragma: no cover
+            return None
+
+    def handle_starttag(self, tag, attrs):
+        # Handle tags that should always be empty and do not specify a closing tag
+        if tag in self.empty_tags and (self.at_line_start() or self.intail):
+            attrs = {key: value if value is not None else key for key, value in attrs}
+            if "markdown" in attrs:
+                attrs.pop('markdown')
+                element = etree.Element(tag, attrs)
+                data = etree.tostring(element, encoding='unicode', method='html')
+            else:
+                data = self.get_starttag_text()
+            self.handle_empty_tag(data, True)
+            return
+
+        if tag in self.block_level_tags and (self.at_line_start() or self.intail):
+            # Valueless attribute (ex: `<tag checked>`) results in `[('checked', None)]`.
+            # Convert to `{'checked': 'checked'}`.
+            attrs = {key: value if value is not None else key for key, value in attrs}
+            state = self.get_state(tag, attrs)
+            if self.inraw or (state in [None, 'off'] and not self.mdstack):
+                # fall back to default behavior
+                attrs.pop('markdown', None)
+                super().handle_starttag(tag, attrs)
+            else:
+                if 'p' in self.mdstack and tag in self.block_level_tags:
+                    # Close unclosed 'p' tag
+                    self.handle_endtag('p')
+                self.mdstate.append(state)
+                self.mdstack.append(tag)
+                attrs['markdown'] = state
+                self.treebuilder.start(tag, attrs)
+        else:
+            # Span level tag
+            if self.inraw:
+                super().handle_starttag(tag, attrs)
+            else:
+                text = self.get_starttag_text()
+                if self.mdstate and self.mdstate[-1] == "off":
+                    self.handle_data(self.md.htmlStash.store(text))
+                else:
+                    self.handle_data(text)
+                if tag in self.CDATA_CONTENT_ELEMENTS:
+                    # This is presumably a standalone tag in a code span (see #1036).
+                    self.clear_cdata_mode()
+
+    def handle_endtag(self, tag):
+        if tag in self.block_level_tags:
+            if self.inraw:
+                super().handle_endtag(tag)
+            elif tag in self.mdstack:
+                # Close element and any unclosed children
+                while self.mdstack:
+                    item = self.mdstack.pop()
+                    self.mdstate.pop()
+                    self.treebuilder.end(item)
+                    if item == tag:
+                        break
+                if not self.mdstack:
+                    # Last item in stack is closed. Stash it
+                    element = self.get_element()
+                    # Get last entry to see if it ends in newlines
+                    # If it is an element, assume there is no newlines
+                    item = self.cleandoc[-1] if self.cleandoc else ''
+                    # If we only have one newline before block element, add another
+                    if not item.endswith('\n\n') and item.endswith('\n'):
+                        self.cleandoc.append('\n')
+                    self.cleandoc.append(self.md.htmlStash.store(element))
+                    self.cleandoc.append('\n\n')
+                    self.state = []
+                    # Check if element has a tail
+                    if not blank_line_re.match(
+                            self.rawdata[self.line_offset + self.offset + len(self.get_endtag_text(tag)):]):
+                        # More content exists after `endtag`.
+                        self.intail = True
+            else:
+                # Treat orphan closing tag as a span level tag.
+                text = self.get_endtag_text(tag)
+                if self.mdstate and self.mdstate[-1] == "off":
+                    self.handle_data(self.md.htmlStash.store(text))
+                else:
+                    self.handle_data(text)
+        else:
+            # Span level tag
+            if self.inraw:
+                super().handle_endtag(tag)
+            else:
+                text = self.get_endtag_text(tag)
+                if self.mdstate and self.mdstate[-1] == "off":
+                    self.handle_data(self.md.htmlStash.store(text))
+                else:
+                    self.handle_data(text)
+
+    def handle_startendtag(self, tag, attrs):
+        if tag in self.empty_tags:
+            attrs = {key: value if value is not None else key for key, value in attrs}
+            if "markdown" in attrs:
+                attrs.pop('markdown')
+                element = etree.Element(tag, attrs)
+                data = etree.tostring(element, encoding='unicode', method='html')
+            else:
+                data = self.get_starttag_text()
+        else:
+            data = self.get_starttag_text()
+        self.handle_empty_tag(data, is_block=self.md.is_block_level(tag))
+
+    def handle_data(self, data):
+        if self.intail and '\n' in data:
+            self.intail = False
+        if self.inraw or not self.mdstack:
+            super().handle_data(data)
+        else:
+            self.treebuilder.data(data)
+
+    def handle_empty_tag(self, data, is_block):
+        if self.inraw or not self.mdstack:
+            super().handle_empty_tag(data, is_block)
+        else:
+            if self.at_line_start() and is_block:
+                self.handle_data('\n' + self.md.htmlStash.store(data) + '\n\n')
+            else:
+                self.handle_data(self.md.htmlStash.store(data))
+
+    def parse_pi(self, i):
+        if self.at_line_start() or self.intail or self.mdstack:
+            # The same override exists in `HTMLExtractor` without the check
+            # for `mdstack`. Therefore, use parent of `HTMLExtractor` instead.
+            return super(HTMLExtractor, self).parse_pi(i)
+        # This is not the beginning of a raw block so treat as plain data
+        # and avoid consuming any tags which may follow (see #1066).
+        self.handle_data('<?')
+        return i + 2
+
+    def parse_html_declaration(self, i):
+        if self.at_line_start() or self.intail or self.mdstack:
+            # The same override exists in `HTMLExtractor` without the check
+            # for `mdstack`. Therefore, use parent of `HTMLExtractor` instead.
+            return super(HTMLExtractor, self).parse_html_declaration(i)
+        # This is not the beginning of a raw block so treat as plain data
+        # and avoid consuming any tags which may follow (see #1066).
+        self.handle_data('<!')
+        return i + 2
+
+
+class HtmlBlockPreprocessor(Preprocessor):
+    """Remove html blocks from the text and store them for later retrieval."""
+
+    def run(self, lines):
+        source = '\n'.join(lines)
+        parser = HTMLExtractorExtra(self.md)
+        parser.feed(source)
+        parser.close()
+        return ''.join(parser.cleandoc).split('\n')
+
+
+class MarkdownInHtmlProcessor(BlockProcessor):
+    """Process Markdown Inside HTML Blocks which have been stored in the `HtmlStash`."""
+
+    def test(self, parent, block):
+        # Always return True. `run` will return `False` it not a valid match.
+        return True
+
+    def parse_element_content(self, element):
+        """
+        Recursively parse the text content of an `etree` Element as Markdown.
+
+        Any block level elements generated from the Markdown will be inserted as children of the element in place
+        of the text content. All `markdown` attributes are removed. For any elements in which Markdown parsing has
+        been disabled, the text content of it and its children are wrapped in an `AtomicString`.
+        """
+
+        md_attr = element.attrib.pop('markdown', 'off')
+
+        if md_attr == 'block':
+            # Parse content as block level
+            # The order in which the different parts are parsed (text, children, tails) is important here as the
+            # order of elements needs to be preserved. We can't be inserting items at a later point in the current
+            # iteration as we don't want to do raw processing on elements created from parsing Markdown text (for
+            # example). Therefore, the order of operations is children, tails, text.
+
+            # Recursively parse existing children from raw HTML
+            for child in list(element):
+                self.parse_element_content(child)
+
+            # Parse Markdown text in tail of children. Do this separate to avoid raw HTML parsing.
+            # Save the position of each item to be inserted later in reverse.
+            tails = []
+            for pos, child in enumerate(element):
+                if child.tail:
+                    block = child.tail.rstrip('\n')
+                    child.tail = ''
+                    # Use a dummy placeholder element.
+                    dummy = etree.Element('div')
+                    self.parser.parseBlocks(dummy, block.split('\n\n'))
+                    children = list(dummy)
+                    children.reverse()
+                    tails.append((pos + 1, children))
+
+            # Insert the elements created from the tails in reverse.
+            tails.reverse()
+            for pos, tail in tails:
+                for item in tail:
+                    element.insert(pos, item)
+
+            # Parse Markdown text content. Do this last to avoid raw HTML parsing.
+            if element.text:
+                block = element.text.rstrip('\n')
+                element.text = ''
+                # Use a dummy placeholder element as the content needs to get inserted before existing children.
+                dummy = etree.Element('div')
+                self.parser.parseBlocks(dummy, block.split('\n\n'))
+                children = list(dummy)
+                children.reverse()
+                for child in children:
+                    element.insert(0, child)
+
+        elif md_attr == 'span':
+            # Span level parsing will be handled by inline processors.
+            # Walk children here to remove any `markdown` attributes.
+            for child in list(element):
+                self.parse_element_content(child)
+
+        else:
+            # Disable inline parsing for everything else
+            if element.text is None:
+                element.text = ''
+            element.text = util.AtomicString(element.text)
+            for child in list(element):
+                self.parse_element_content(child)
+                if child.tail:
+                    child.tail = util.AtomicString(child.tail)
+
+    def run(self, parent, blocks):
+        m = util.HTML_PLACEHOLDER_RE.match(blocks[0])
+        if m:
+            index = int(m.group(1))
+            element = self.parser.md.htmlStash.rawHtmlBlocks[index]
+            if isinstance(element, etree.Element):
+                # We have a matched element. Process it.
+                blocks.pop(0)
+                self.parse_element_content(element)
+                parent.append(element)
+                # Cleanup stash. Replace element with empty string to avoid confusing postprocessor.
+                self.parser.md.htmlStash.rawHtmlBlocks.pop(index)
+                self.parser.md.htmlStash.rawHtmlBlocks.insert(index, '')
+                # Confirm the match to the `blockparser`.
+                return True
+        # No match found.
+        return False
+
+
+class MarkdownInHTMLPostprocessor(RawHtmlPostprocessor):
+    def stash_to_string(self, text):
+        """ Override default to handle any `etree` elements still in the stash. """
+        if isinstance(text, etree.Element):
+            return self.md.serializer(text)
+        else:
+            return str(text)
+
+
+class MarkdownInHtmlExtension(Extension):
+    """Add Markdown parsing in HTML to Markdown class."""
+
+    def extendMarkdown(self, md):
+        """ Register extension instances. """
+
+        # Replace raw HTML preprocessor
+        md.preprocessors.register(HtmlBlockPreprocessor(md), 'html_block', 20)
+        # Add `blockprocessor` which handles the placeholders for `etree` elements
+        md.parser.blockprocessors.register(
+            MarkdownInHtmlProcessor(md.parser), 'markdown_block', 105
+        )
+        # Replace raw HTML postprocessor
+        md.postprocessors.register(MarkdownInHTMLPostprocessor(md), 'raw_html', 30)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return MarkdownInHtmlExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/meta.py

@@ -0,0 +1,85 @@
+# Meta Data Extension for Python-Markdown
+# =======================================
+
+# This extension adds Meta Data handling to markdown.
+
+# See https://Python-Markdown.github.io/extensions/meta_data
+# for documentation.
+
+# Original code Copyright 2007-2008 [Waylan Limberg](http://achinghead.com).
+
+# All changes Copyright 2008-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+This extension adds Meta Data handling to markdown.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/meta_data)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..preprocessors import Preprocessor
+import re
+import logging
+
+log = logging.getLogger('MARKDOWN')
+
+# Global Vars
+META_RE = re.compile(r'^[ ]{0,3}(?P<key>[A-Za-z0-9_-]+):\s*(?P<value>.*)')
+META_MORE_RE = re.compile(r'^[ ]{4,}(?P<value>.*)')
+BEGIN_RE = re.compile(r'^-{3}(\s.*)?')
+END_RE = re.compile(r'^(-{3}|\.{3})(\s.*)?')
+
+
+class MetaExtension (Extension):
+    """ Meta-Data extension for Python-Markdown. """
+
+    def extendMarkdown(self, md):
+        """ Add `MetaPreprocessor` to Markdown instance. """
+        md.registerExtension(self)
+        self.md = md
+        md.preprocessors.register(MetaPreprocessor(md), 'meta', 27)
+
+    def reset(self) -> None:
+        self.md.Meta = {}
+
+
+class MetaPreprocessor(Preprocessor):
+    """ Get Meta-Data. """
+
+    def run(self, lines):
+        """ Parse Meta-Data and store in Markdown.Meta. """
+        meta = {}
+        key = None
+        if lines and BEGIN_RE.match(lines[0]):
+            lines.pop(0)
+        while lines:
+            line = lines.pop(0)
+            m1 = META_RE.match(line)
+            if line.strip() == '' or END_RE.match(line):
+                break  # blank line or end of YAML header - done
+            if m1:
+                key = m1.group('key').lower().strip()
+                value = m1.group('value').strip()
+                try:
+                    meta[key].append(value)
+                except KeyError:
+                    meta[key] = [value]
+            else:
+                m2 = META_MORE_RE.match(line)
+                if m2 and key:
+                    # Add another line to existing key
+                    meta[key].append(m2.group('value').strip())
+                else:
+                    lines.insert(0, line)
+                    break  # no meta data - done
+        self.md.Meta = meta
+        return lines
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return MetaExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/nl2br.py

@@ -0,0 +1,41 @@
+# `NL2BR` Extension
+# ===============
+
+# A Python-Markdown extension to treat newlines as hard breaks; like
+# GitHub-flavored Markdown does.
+
+# See https://Python-Markdown.github.io/extensions/nl2br
+# for documentation.
+
+# Original code Copyright 2011 [Brian Neal](https://deathofagremmie.com/)
+
+# All changes Copyright 2011-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+A Python-Markdown extension to treat newlines as hard breaks; like
+GitHub-flavored Markdown does.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/nl2br)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..inlinepatterns import SubstituteTagInlineProcessor
+
+BR_RE = r'\n'
+
+
+class Nl2BrExtension(Extension):
+
+    def extendMarkdown(self, md):
+        """ Add a `SubstituteTagInlineProcessor` to Markdown. """
+        br_tag = SubstituteTagInlineProcessor(BR_RE, 'br')
+        md.inlinePatterns.register(br_tag, 'nl', 5)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return Nl2BrExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/sane_lists.py

@@ -0,0 +1,65 @@
+# Sane List Extension for Python-Markdown
+# =======================================
+
+# Modify the behavior of Lists in Python-Markdown to act in a sane manor.
+
+# See https://Python-Markdown.github.io/extensions/sane_lists
+# for documentation.
+
+# Original code Copyright 2011 [Waylan Limberg](http://achinghead.com)
+
+# All changes Copyright 2011-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+Modify the behavior of Lists in Python-Markdown to act in a sane manor.
+
+See [documentation](https://Python-Markdown.github.io/extensions/sane_lists)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..blockprocessors import OListProcessor, UListProcessor
+import re
+
+
+class SaneOListProcessor(OListProcessor):
+    """ Override `SIBLING_TAGS` to not include `ul` and set `LAZY_OL` to `False`. """
+
+    SIBLING_TAGS = ['ol']
+    """ Exclude `ul` from list of siblings. """
+    LAZY_OL = False
+    """ Disable lazy list behavior. """
+
+    def __init__(self, parser):
+        super().__init__(parser)
+        self.CHILD_RE = re.compile(r'^[ ]{0,%d}((\d+\.))[ ]+(.*)' %
+                                   (self.tab_length - 1))
+
+
+class SaneUListProcessor(UListProcessor):
+    """ Override `SIBLING_TAGS` to not include `ol`. """
+
+    SIBLING_TAGS = ['ul']
+    """ Exclude `ol` from list of siblings. """
+
+    def __init__(self, parser):
+        super().__init__(parser)
+        self.CHILD_RE = re.compile(r'^[ ]{0,%d}(([*+-]))[ ]+(.*)' %
+                                   (self.tab_length - 1))
+
+
+class SaneListExtension(Extension):
+    """ Add sane lists to Markdown. """
+
+    def extendMarkdown(self, md):
+        """ Override existing Processors. """
+        md.parser.blockprocessors.register(SaneOListProcessor(md.parser), 'olist', 40)
+        md.parser.blockprocessors.register(SaneUListProcessor(md.parser), 'ulist', 30)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return SaneListExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/smarty.py

@@ -0,0 +1,265 @@
+# Smarty extension for Python-Markdown
+# ====================================
+
+# Adds conversion of ASCII dashes, quotes and ellipses to their HTML
+# entity equivalents.
+
+# See https://Python-Markdown.github.io/extensions/smarty
+# for documentation.
+
+# Author: 2013, Dmitry Shachnev <mitya57@gmail.com>
+
+# All changes Copyright 2013-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+# SmartyPants license:
+
+#    Copyright (c) 2003 John Gruber <https://daringfireball.net/>
+#    All rights reserved.
+
+#    Redistribution and use in source and binary forms, with or without
+#    modification, are permitted provided that the following conditions are
+#    met:
+
+#    *  Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+
+#    *  Redistributions in binary form must reproduce the above copyright
+#       notice, this list of conditions and the following disclaimer in
+#       the documentation and/or other materials provided with the
+#       distribution.
+
+#    *  Neither the name "SmartyPants" nor the names of its contributors
+#       may be used to endorse or promote products derived from this
+#       software without specific prior written permission.
+
+#    This software is provided by the copyright holders and contributors "as
+#    is" and any express or implied warranties, including, but not limited
+#    to, the implied warranties of merchantability and fitness for a
+#    particular purpose are disclaimed. In no event shall the copyright
+#    owner or contributors be liable for any direct, indirect, incidental,
+#    special, exemplary, or consequential damages (including, but not
+#    limited to, procurement of substitute goods or services; loss of use,
+#    data, or profits; or business interruption) however caused and on any
+#    theory of liability, whether in contract, strict liability, or tort
+#    (including negligence or otherwise) arising in any way out of the use
+#    of this software, even if advised of the possibility of such damage.
+
+
+# `smartypants.py` license:
+
+#    `smartypants.py` is a derivative work of SmartyPants.
+#    Copyright (c) 2004, 2007 Chad Miller <http://web.chad.org/>
+
+#    Redistribution and use in source and binary forms, with or without
+#    modification, are permitted provided that the following conditions are
+#    met:
+
+#    *  Redistributions of source code must retain the above copyright
+#       notice, this list of conditions and the following disclaimer.
+
+#    *  Redistributions in binary form must reproduce the above copyright
+#       notice, this list of conditions and the following disclaimer in
+#       the documentation and/or other materials provided with the
+#       distribution.
+
+#    This software is provided by the copyright holders and contributors "as
+#    is" and any express or implied warranties, including, but not limited
+#    to, the implied warranties of merchantability and fitness for a
+#    particular purpose are disclaimed. In no event shall the copyright
+#    owner or contributors be liable for any direct, indirect, incidental,
+#    special, exemplary, or consequential damages (including, but not
+#    limited to, procurement of substitute goods or services; loss of use,
+#    data, or profits; or business interruption) however caused and on any
+#    theory of liability, whether in contract, strict liability, or tort
+#    (including negligence or otherwise) arising in any way out of the use
+#    of this software, even if advised of the possibility of such damage.
+
+"""
+Adds conversion of ASCII dashes, quotes and ellipses to their HTML
+entity equivalents.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/smarty)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..inlinepatterns import HtmlInlineProcessor, HTML_RE
+from ..treeprocessors import InlineProcessor
+from ..util import Registry
+
+
+# Constants for quote education.
+punctClass = r"""[!"#\$\%'()*+,-.\/:;<=>?\@\[\\\]\^_`{|}~]"""
+endOfWordClass = r"[\s.,;:!?)]"
+closeClass = r"[^\ \t\r\n\[\{\(\-\u0002\u0003]"
+
+openingQuotesBase = (
+    r'(\s'               # a  whitespace char
+    r'|&nbsp;'           # or a non-breaking space entity
+    r'|--'               # or dashes
+    r'|–|—'              # or Unicode
+    r'|&[mn]dash;'       # or named dash entities
+    r'|&#8211;|&#8212;'  # or decimal entities
+    r')'
+)
+
+substitutions = {
+    'mdash': '&mdash;',
+    'ndash': '&ndash;',
+    'ellipsis': '&hellip;',
+    'left-angle-quote': '&laquo;',
+    'right-angle-quote': '&raquo;',
+    'left-single-quote': '&lsquo;',
+    'right-single-quote': '&rsquo;',
+    'left-double-quote': '&ldquo;',
+    'right-double-quote': '&rdquo;',
+}
+
+
+# Special case if the very first character is a quote
+# followed by punctuation at a non-word-break. Close the quotes by brute force:
+singleQuoteStartRe = r"^'(?=%s\B)" % punctClass
+doubleQuoteStartRe = r'^"(?=%s\B)' % punctClass
+
+# Special case for double sets of quotes, e.g.:
+#   <p>He said, "'Quoted' words in a larger quote."</p>
+doubleQuoteSetsRe = r""""'(?=\w)"""
+singleQuoteSetsRe = r"""'"(?=\w)"""
+
+# Special case for decade abbreviations (the '80s):
+decadeAbbrRe = r"(?<!\w)'(?=\d{2}s)"
+
+# Get most opening double quotes:
+openingDoubleQuotesRegex = r'%s"(?=\w)' % openingQuotesBase
+
+# Double closing quotes:
+closingDoubleQuotesRegex = r'"(?=\s)'
+closingDoubleQuotesRegex2 = '(?<=%s)"' % closeClass
+
+# Get most opening single quotes:
+openingSingleQuotesRegex = r"%s'(?=\w)" % openingQuotesBase
+
+# Single closing quotes:
+closingSingleQuotesRegex = r"(?<=%s)'(?!\s|s\b|\d)" % closeClass
+closingSingleQuotesRegex2 = r"'(\s|s\b)"
+
+# All remaining quotes should be opening ones
+remainingSingleQuotesRegex = r"'"
+remainingDoubleQuotesRegex = r'"'
+
+HTML_STRICT_RE = HTML_RE + r'(?!\>)'
+
+
+class SubstituteTextPattern(HtmlInlineProcessor):
+    def __init__(self, pattern, replace, md):
+        """ Replaces matches with some text. """
+        HtmlInlineProcessor.__init__(self, pattern)
+        self.replace = replace
+        self.md = md
+
+    def handleMatch(self, m, data):
+        result = ''
+        for part in self.replace:
+            if isinstance(part, int):
+                result += m.group(part)
+            else:
+                result += self.md.htmlStash.store(part)
+        return result, m.start(0), m.end(0)
+
+
+class SmartyExtension(Extension):
+    """ Add Smarty to Markdown. """
+    def __init__(self, **kwargs):
+        self.config = {
+            'smart_quotes': [True, 'Educate quotes'],
+            'smart_angled_quotes': [False, 'Educate angled quotes'],
+            'smart_dashes': [True, 'Educate dashes'],
+            'smart_ellipses': [True, 'Educate ellipses'],
+            'substitutions': [{}, 'Overwrite default substitutions'],
+        }
+        """ Default configuration options. """
+        super().__init__(**kwargs)
+        self.substitutions = dict(substitutions)
+        self.substitutions.update(self.getConfig('substitutions', default={}))
+
+    def _addPatterns(self, md, patterns, serie, priority):
+        for ind, pattern in enumerate(patterns):
+            pattern += (md,)
+            pattern = SubstituteTextPattern(*pattern)
+            name = 'smarty-%s-%d' % (serie, ind)
+            self.inlinePatterns.register(pattern, name, priority-ind)
+
+    def educateDashes(self, md) -> None:
+        emDashesPattern = SubstituteTextPattern(
+            r'(?<!-)---(?!-)', (self.substitutions['mdash'],), md
+        )
+        enDashesPattern = SubstituteTextPattern(
+            r'(?<!-)--(?!-)', (self.substitutions['ndash'],), md
+        )
+        self.inlinePatterns.register(emDashesPattern, 'smarty-em-dashes', 50)
+        self.inlinePatterns.register(enDashesPattern, 'smarty-en-dashes', 45)
+
+    def educateEllipses(self, md) -> None:
+        ellipsesPattern = SubstituteTextPattern(
+            r'(?<!\.)\.{3}(?!\.)', (self.substitutions['ellipsis'],), md
+        )
+        self.inlinePatterns.register(ellipsesPattern, 'smarty-ellipses', 10)
+
+    def educateAngledQuotes(self, md) -> None:
+        leftAngledQuotePattern = SubstituteTextPattern(
+            r'\<\<', (self.substitutions['left-angle-quote'],), md
+        )
+        rightAngledQuotePattern = SubstituteTextPattern(
+            r'\>\>', (self.substitutions['right-angle-quote'],), md
+        )
+        self.inlinePatterns.register(leftAngledQuotePattern, 'smarty-left-angle-quotes', 40)
+        self.inlinePatterns.register(rightAngledQuotePattern, 'smarty-right-angle-quotes', 35)
+
+    def educateQuotes(self, md) -> None:
+        lsquo = self.substitutions['left-single-quote']
+        rsquo = self.substitutions['right-single-quote']
+        ldquo = self.substitutions['left-double-quote']
+        rdquo = self.substitutions['right-double-quote']
+        patterns = (
+            (singleQuoteStartRe, (rsquo,)),
+            (doubleQuoteStartRe, (rdquo,)),
+            (doubleQuoteSetsRe, (ldquo + lsquo,)),
+            (singleQuoteSetsRe, (lsquo + ldquo,)),
+            (decadeAbbrRe, (rsquo,)),
+            (openingSingleQuotesRegex, (1, lsquo)),
+            (closingSingleQuotesRegex, (rsquo,)),
+            (closingSingleQuotesRegex2, (rsquo, 1)),
+            (remainingSingleQuotesRegex, (lsquo,)),
+            (openingDoubleQuotesRegex, (1, ldquo)),
+            (closingDoubleQuotesRegex, (rdquo,)),
+            (closingDoubleQuotesRegex2, (rdquo,)),
+            (remainingDoubleQuotesRegex, (ldquo,))
+        )
+        self._addPatterns(md, patterns, 'quotes', 30)
+
+    def extendMarkdown(self, md):
+        configs = self.getConfigs()
+        self.inlinePatterns: Registry[HtmlInlineProcessor] = Registry()
+        if configs['smart_ellipses']:
+            self.educateEllipses(md)
+        if configs['smart_quotes']:
+            self.educateQuotes(md)
+        if configs['smart_angled_quotes']:
+            self.educateAngledQuotes(md)
+            # Override `HTML_RE` from `inlinepatterns.py` so that it does not
+            # process tags with duplicate closing quotes.
+            md.inlinePatterns.register(HtmlInlineProcessor(HTML_STRICT_RE, md), 'html', 90)
+        if configs['smart_dashes']:
+            self.educateDashes(md)
+        inlineProcessor = InlineProcessor(md)
+        inlineProcessor.inlinePatterns = self.inlinePatterns
+        md.treeprocessors.register(inlineProcessor, 'smarty', 2)
+        md.ESCAPED_CHARS.extend(['"', "'"])
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return SmartyExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/tables.py

@@ -0,0 +1,243 @@
+# Tables Extension for Python-Markdown
+# ====================================
+
+# Added parsing of tables to Python-Markdown.
+
+# See https://Python-Markdown.github.io/extensions/tables
+# for documentation.
+
+# Original code Copyright 2009 [Waylan Limberg](http://achinghead.com)
+
+# All changes Copyright 2008-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+Added parsing of tables to Python-Markdown.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/tables)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..blockprocessors import BlockProcessor
+import xml.etree.ElementTree as etree
+import re
+PIPE_NONE = 0
+PIPE_LEFT = 1
+PIPE_RIGHT = 2
+
+
+class TableProcessor(BlockProcessor):
+    """ Process Tables. """
+
+    RE_CODE_PIPES = re.compile(r'(?:(\\\\)|(\\`+)|(`+)|(\\\|)|(\|))')
+    RE_END_BORDER = re.compile(r'(?<!\\)(?:\\\\)*\|$')
+
+    def __init__(self, parser, config):
+        self.border = False
+        self.separator = ''
+        self.config = config
+
+        super().__init__(parser)
+
+    def test(self, parent, block):
+        """
+        Ensure first two rows (column header and separator row) are valid table rows.
+
+        Keep border check and separator row do avoid repeating the work.
+        """
+        is_table = False
+        rows = [row.strip(' ') for row in block.split('\n')]
+        if len(rows) > 1:
+            header0 = rows[0]
+            self.border = PIPE_NONE
+            if header0.startswith('|'):
+                self.border |= PIPE_LEFT
+            if self.RE_END_BORDER.search(header0) is not None:
+                self.border |= PIPE_RIGHT
+            row = self._split_row(header0)
+            row0_len = len(row)
+            is_table = row0_len > 1
+
+            # Each row in a single column table needs at least one pipe.
+            if not is_table and row0_len == 1 and self.border:
+                for index in range(1, len(rows)):
+                    is_table = rows[index].startswith('|')
+                    if not is_table:
+                        is_table = self.RE_END_BORDER.search(rows[index]) is not None
+                    if not is_table:
+                        break
+
+            if is_table:
+                row = self._split_row(rows[1])
+                is_table = (len(row) == row0_len) and set(''.join(row)) <= set('|:- ')
+                if is_table:
+                    self.separator = row
+
+        return is_table
+
+    def run(self, parent, blocks):
+        """ Parse a table block and build table. """
+        block = blocks.pop(0).split('\n')
+        header = block[0].strip(' ')
+        rows = [] if len(block) < 3 else block[2:]
+
+        # Get alignment of columns
+        align = []
+        for c in self.separator:
+            c = c.strip(' ')
+            if c.startswith(':') and c.endswith(':'):
+                align.append('center')
+            elif c.startswith(':'):
+                align.append('left')
+            elif c.endswith(':'):
+                align.append('right')
+            else:
+                align.append(None)
+
+        # Build table
+        table = etree.SubElement(parent, 'table')
+        thead = etree.SubElement(table, 'thead')
+        self._build_row(header, thead, align)
+        tbody = etree.SubElement(table, 'tbody')
+        if len(rows) == 0:
+            # Handle empty table
+            self._build_empty_row(tbody, align)
+        else:
+            for row in rows:
+                self._build_row(row.strip(' '), tbody, align)
+
+    def _build_empty_row(self, parent, align):
+        """Build an empty row."""
+        tr = etree.SubElement(parent, 'tr')
+        count = len(align)
+        while count:
+            etree.SubElement(tr, 'td')
+            count -= 1
+
+    def _build_row(self, row, parent, align):
+        """ Given a row of text, build table cells. """
+        tr = etree.SubElement(parent, 'tr')
+        tag = 'td'
+        if parent.tag == 'thead':
+            tag = 'th'
+        cells = self._split_row(row)
+        # We use align here rather than cells to ensure every row
+        # contains the same number of columns.
+        for i, a in enumerate(align):
+            c = etree.SubElement(tr, tag)
+            try:
+                c.text = cells[i].strip(' ')
+            except IndexError:  # pragma: no cover
+                c.text = ""
+            if a:
+                if self.config['use_align_attribute']:
+                    c.set('align', a)
+                else:
+                    c.set('style', f'text-align: {a};')
+
+    def _split_row(self, row):
+        """ split a row of text into list of cells. """
+        if self.border:
+            if row.startswith('|'):
+                row = row[1:]
+            row = self.RE_END_BORDER.sub('', row)
+        return self._split(row)
+
+    def _split(self, row):
+        """ split a row of text with some code into a list of cells. """
+        elements = []
+        pipes = []
+        tics = []
+        tic_points = []
+        tic_region = []
+        good_pipes = []
+
+        # Parse row
+        # Throw out \\, and \|
+        for m in self.RE_CODE_PIPES.finditer(row):
+            # Store ` data (len, start_pos, end_pos)
+            if m.group(2):
+                # \`+
+                # Store length of each tic group: subtract \
+                tics.append(len(m.group(2)) - 1)
+                # Store start of group, end of group, and escape length
+                tic_points.append((m.start(2), m.end(2) - 1, 1))
+            elif m.group(3):
+                # `+
+                # Store length of each tic group
+                tics.append(len(m.group(3)))
+                # Store start of group, end of group, and escape length
+                tic_points.append((m.start(3), m.end(3) - 1, 0))
+            # Store pipe location
+            elif m.group(5):
+                pipes.append(m.start(5))
+
+        # Pair up tics according to size if possible
+        # Subtract the escape length *only* from the opening.
+        # Walk through tic list and see if tic has a close.
+        # Store the tic region (start of region, end of region).
+        pos = 0
+        tic_len = len(tics)
+        while pos < tic_len:
+            try:
+                tic_size = tics[pos] - tic_points[pos][2]
+                if tic_size == 0:
+                    raise ValueError
+                index = tics[pos + 1:].index(tic_size) + 1
+                tic_region.append((tic_points[pos][0], tic_points[pos + index][1]))
+                pos += index + 1
+            except ValueError:
+                pos += 1
+
+        # Resolve pipes.  Check if they are within a tic pair region.
+        # Walk through pipes comparing them to each region.
+        #     - If pipe position is less that a region, it isn't in a region
+        #     - If it is within a region, we don't want it, so throw it out
+        #     - If we didn't throw it out, it must be a table pipe
+        for pipe in pipes:
+            throw_out = False
+            for region in tic_region:
+                if pipe < region[0]:
+                    # Pipe is not in a region
+                    break
+                elif region[0] <= pipe <= region[1]:
+                    # Pipe is within a code region.  Throw it out.
+                    throw_out = True
+                    break
+            if not throw_out:
+                good_pipes.append(pipe)
+
+        # Split row according to table delimiters.
+        pos = 0
+        for pipe in good_pipes:
+            elements.append(row[pos:pipe])
+            pos = pipe + 1
+        elements.append(row[pos:])
+        return elements
+
+
+class TableExtension(Extension):
+    """ Add tables to Markdown. """
+
+    def __init__(self, **kwargs):
+        self.config = {
+            'use_align_attribute': [False, 'True to use align attribute instead of style.'],
+        }
+        """ Default configuration options. """
+
+        super().__init__(**kwargs)
+
+    def extendMarkdown(self, md):
+        """ Add an instance of `TableProcessor` to `BlockParser`. """
+        if '|' not in md.ESCAPED_CHARS:
+            md.ESCAPED_CHARS.append('|')
+        processor = TableProcessor(md.parser, self.getConfigs())
+        md.parser.blockprocessors.register(processor, 'table', 75)
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return TableExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/toc.py

@@ -0,0 +1,408 @@
+# Table of Contents Extension for Python-Markdown
+# ===============================================
+
+# See https://Python-Markdown.github.io/extensions/toc
+# for documentation.
+
+# Original code Copyright 2008 [Jack Miller](https://codezen.org/)
+
+# All changes Copyright 2008-2014 The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+Add table of contents support to Python-Markdown.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/toc)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..treeprocessors import Treeprocessor
+from ..util import code_escape, parseBoolValue, AMP_SUBSTITUTE, HTML_PLACEHOLDER_RE, AtomicString
+from ..treeprocessors import UnescapeTreeprocessor
+import re
+import html
+import unicodedata
+import xml.etree.ElementTree as etree
+
+
+def slugify(value, separator, unicode=False):
+    """ Slugify a string, to make it URL friendly. """
+    if not unicode:
+        # Replace Extended Latin characters with ASCII, i.e. `žlutý` => `zluty`
+        value = unicodedata.normalize('NFKD', value)
+        value = value.encode('ascii', 'ignore').decode('ascii')
+    value = re.sub(r'[^\w\s-]', '', value).strip().lower()
+    return re.sub(r'[{}\s]+'.format(separator), separator, value)
+
+
+def slugify_unicode(value, separator):
+    """ Slugify a string, to make it URL friendly while preserving Unicode characters. """
+    return slugify(value, separator, unicode=True)
+
+
+IDCOUNT_RE = re.compile(r'^(.*)_([0-9]+)$')
+
+
+def unique(id, ids):
+    """ Ensure id is unique in set of ids. Append '_1', '_2'... if not """
+    while id in ids or not id:
+        m = IDCOUNT_RE.match(id)
+        if m:
+            id = '%s_%d' % (m.group(1), int(m.group(2))+1)
+        else:
+            id = '%s_%d' % (id, 1)
+    ids.add(id)
+    return id
+
+
+def get_name(el):
+    """Get title name."""
+
+    text = []
+    for c in el.itertext():
+        if isinstance(c, AtomicString):
+            text.append(html.unescape(c))
+        else:
+            text.append(c)
+    return ''.join(text).strip()
+
+
+def stashedHTML2text(text, md, strip_entities: bool = True):
+    """ Extract raw HTML from stash, reduce to plain text and swap with placeholder. """
+    def _html_sub(m):
+        """ Substitute raw html with plain text. """
+        try:
+            raw = md.htmlStash.rawHtmlBlocks[int(m.group(1))]
+        except (IndexError, TypeError):  # pragma: no cover
+            return m.group(0)
+        # Strip out tags and/or entities - leaving text
+        res = re.sub(r'(<[^>]+>)', '', raw)
+        if strip_entities:
+            res = re.sub(r'(&[\#a-zA-Z0-9]+;)', '', res)
+        return res
+
+    return HTML_PLACEHOLDER_RE.sub(_html_sub, text)
+
+
+def unescape(text):
+    """ Unescape escaped text. """
+    c = UnescapeTreeprocessor()
+    return c.unescape(text)
+
+
+def nest_toc_tokens(toc_list):
+    """Given an unsorted list with errors and skips, return a nested one.
+
+        [{'level': 1}, {'level': 2}]
+        =>
+        [{'level': 1, 'children': [{'level': 2, 'children': []}]}]
+
+    A wrong list is also converted:
+
+        [{'level': 2}, {'level': 1}]
+        =>
+        [{'level': 2, 'children': []}, {'level': 1, 'children': []}]
+    """
+
+    ordered_list = []
+    if len(toc_list):
+        # Initialize everything by processing the first entry
+        last = toc_list.pop(0)
+        last['children'] = []
+        levels = [last['level']]
+        ordered_list.append(last)
+        parents = []
+
+        # Walk the rest nesting the entries properly
+        while toc_list:
+            t = toc_list.pop(0)
+            current_level = t['level']
+            t['children'] = []
+
+            # Reduce depth if current level < last item's level
+            if current_level < levels[-1]:
+                # Pop last level since we know we are less than it
+                levels.pop()
+
+                # Pop parents and levels we are less than or equal to
+                to_pop = 0
+                for p in reversed(parents):
+                    if current_level <= p['level']:
+                        to_pop += 1
+                    else:  # pragma: no cover
+                        break
+                if to_pop:
+                    levels = levels[:-to_pop]
+                    parents = parents[:-to_pop]
+
+                # Note current level as last
+                levels.append(current_level)
+
+            # Level is the same, so append to
+            # the current parent (if available)
+            if current_level == levels[-1]:
+                (parents[-1]['children'] if parents
+                 else ordered_list).append(t)
+
+            # Current level is > last item's level,
+            # So make last item a parent and append current as child
+            else:
+                last['children'].append(t)
+                parents.append(last)
+                levels.append(current_level)
+            last = t
+
+    return ordered_list
+
+
+class TocTreeprocessor(Treeprocessor):
+    """ Step through document and build TOC. """
+
+    def __init__(self, md, config):
+        super().__init__(md)
+
+        self.marker = config["marker"]
+        self.title = config["title"]
+        self.base_level = int(config["baselevel"]) - 1
+        self.slugify = config["slugify"]
+        self.sep = config["separator"]
+        self.toc_class = config["toc_class"]
+        self.title_class = config["title_class"]
+        self.use_anchors = parseBoolValue(config["anchorlink"])
+        self.anchorlink_class = config["anchorlink_class"]
+        self.use_permalinks = parseBoolValue(config["permalink"], False)
+        if self.use_permalinks is None:
+            self.use_permalinks = config["permalink"]
+        self.permalink_class = config["permalink_class"]
+        self.permalink_title = config["permalink_title"]
+        self.permalink_leading = parseBoolValue(config["permalink_leading"], False)
+        self.header_rgx = re.compile("[Hh][123456]")
+        if isinstance(config["toc_depth"], str) and '-' in config["toc_depth"]:
+            self.toc_top, self.toc_bottom = [int(x) for x in config["toc_depth"].split('-')]
+        else:
+            self.toc_top = 1
+            self.toc_bottom = int(config["toc_depth"])
+
+    def iterparent(self, node):
+        """ Iterator wrapper to get allowed parent and child all at once. """
+
+        # We do not allow the marker inside a header as that
+        # would causes an endless loop of placing a new TOC
+        # inside previously generated TOC.
+        for child in node:
+            if not self.header_rgx.match(child.tag) and child.tag not in ['pre', 'code']:
+                yield node, child
+                yield from self.iterparent(child)
+
+    def replace_marker(self, root, elem) -> None:
+        """ Replace marker with elem. """
+        for (p, c) in self.iterparent(root):
+            text = ''.join(c.itertext()).strip()
+            if not text:
+                continue
+
+            # To keep the output from screwing up the
+            # validation by putting a `<div>` inside of a `<p>`
+            # we actually replace the `<p>` in its entirety.
+
+            # The `<p>` element may contain more than a single text content
+            # (`nl2br` can introduce a `<br>`). In this situation, `c.text` returns
+            # the very first content, ignore children contents or tail content.
+            # `len(c) == 0` is here to ensure there is only text in the `<p>`.
+            if c.text and c.text.strip() == self.marker and len(c) == 0:
+                for i in range(len(p)):
+                    if p[i] == c:
+                        p[i] = elem
+                        break
+
+    def set_level(self, elem) -> None:
+        """ Adjust header level according to base level. """
+        level = int(elem.tag[-1]) + self.base_level
+        if level > 6:
+            level = 6
+        elem.tag = 'h%d' % level
+
+    def add_anchor(self, c, elem_id) -> None:
+        anchor = etree.Element("a")
+        anchor.text = c.text
+        anchor.attrib["href"] = "#" + elem_id
+        anchor.attrib["class"] = self.anchorlink_class
+        c.text = ""
+        for elem in c:
+            anchor.append(elem)
+        while len(c):
+            c.remove(c[0])
+        c.append(anchor)
+
+    def add_permalink(self, c, elem_id) -> None:
+        permalink = etree.Element("a")
+        permalink.text = ("%spara;" % AMP_SUBSTITUTE
+                          if self.use_permalinks is True
+                          else self.use_permalinks)
+        permalink.attrib["href"] = "#" + elem_id
+        permalink.attrib["class"] = self.permalink_class
+        if self.permalink_title:
+            permalink.attrib["title"] = self.permalink_title
+        if self.permalink_leading:
+            permalink.tail = c.text
+            c.text = ""
+            c.insert(0, permalink)
+        else:
+            c.append(permalink)
+
+    def build_toc_div(self, toc_list):
+        """ Return a string div given a toc list. """
+        div = etree.Element("div")
+        div.attrib["class"] = self.toc_class
+
+        # Add title to the div
+        if self.title:
+            header = etree.SubElement(div, "span")
+            if self.title_class:
+                header.attrib["class"] = self.title_class
+            header.text = self.title
+
+        def build_etree_ul(toc_list, parent):
+            ul = etree.SubElement(parent, "ul")
+            for item in toc_list:
+                # List item link, to be inserted into the toc div
+                li = etree.SubElement(ul, "li")
+                link = etree.SubElement(li, "a")
+                link.text = item.get('name', '')
+                link.attrib["href"] = '#' + item.get('id', '')
+                if item['children']:
+                    build_etree_ul(item['children'], li)
+            return ul
+
+        build_etree_ul(toc_list, div)
+
+        if 'prettify' in self.md.treeprocessors:
+            self.md.treeprocessors['prettify'].run(div)
+
+        return div
+
+    def run(self, doc):
+        # Get a list of id attributes
+        used_ids = set()
+        for el in doc.iter():
+            if "id" in el.attrib:
+                used_ids.add(el.attrib["id"])
+
+        toc_tokens = []
+        for el in doc.iter():
+            if isinstance(el.tag, str) and self.header_rgx.match(el.tag):
+                self.set_level(el)
+                text = get_name(el)
+
+                # Do not override pre-existing ids
+                if "id" not in el.attrib:
+                    innertext = unescape(stashedHTML2text(text, self.md))
+                    el.attrib["id"] = unique(self.slugify(innertext, self.sep), used_ids)
+
+                if int(el.tag[-1]) >= self.toc_top and int(el.tag[-1]) <= self.toc_bottom:
+                    toc_tokens.append({
+                        'level': int(el.tag[-1]),
+                        'id': el.attrib["id"],
+                        'name': unescape(stashedHTML2text(
+                            code_escape(el.attrib.get('data-toc-label', text)),
+                            self.md, strip_entities=False
+                        ))
+                    })
+
+                # Remove the data-toc-label attribute as it is no longer needed
+                if 'data-toc-label' in el.attrib:
+                    del el.attrib['data-toc-label']
+
+                if self.use_anchors:
+                    self.add_anchor(el, el.attrib["id"])
+                if self.use_permalinks not in [False, None]:
+                    self.add_permalink(el, el.attrib["id"])
+
+        toc_tokens = nest_toc_tokens(toc_tokens)
+        div = self.build_toc_div(toc_tokens)
+        if self.marker:
+            self.replace_marker(doc, div)
+
+        # serialize and attach to markdown instance.
+        toc = self.md.serializer(div)
+        for pp in self.md.postprocessors:
+            toc = pp.run(toc)
+        self.md.toc_tokens = toc_tokens
+        self.md.toc = toc
+
+
+class TocExtension(Extension):
+
+    TreeProcessorClass = TocTreeprocessor
+
+    def __init__(self, **kwargs):
+        self.config = {
+            'marker': [
+                '[TOC]',
+                'Text to find and replace with Table of Contents. Set to an empty string to disable. '
+                'Default: `[TOC]`.'
+            ],
+            'title': [
+                '', 'Title to insert into TOC `<div>`. Default: an empty string.'
+            ],
+            'title_class': [
+                'toctitle', 'CSS class used for the title. Default: `toctitle`.'
+            ],
+            'toc_class': [
+                'toc', 'CSS class(es) used for the link. Default: `toclink`.'
+            ],
+            'anchorlink': [
+                False, 'True if header should be a self link. Default: `False`.'
+            ],
+            'anchorlink_class': [
+                'toclink', 'CSS class(es) used for the link. Defaults: `toclink`.'
+            ],
+            'permalink': [
+                0, 'True or link text if a Sphinx-style permalink should be added. Default: `False`.'
+            ],
+            'permalink_class': [
+                'headerlink', 'CSS class(es) used for the link. Default: `headerlink`.'
+            ],
+            'permalink_title': [
+                'Permanent link', 'Title attribute of the permalink. Default: `Permanent link`.'
+            ],
+            'permalink_leading': [
+                False,
+                'True if permalinks should be placed at start of the header, rather than end. Default: False.'
+            ],
+            'baselevel': ['1', 'Base level for headers. Default: `1`.'],
+            'slugify': [
+                slugify, 'Function to generate anchors based on header text. Default: `slugify`.'
+            ],
+            'separator': ['-', 'Word separator. Default: `-`.'],
+            'toc_depth': [
+                6,
+                'Define the range of section levels to include in the Table of Contents. A single integer '
+                '(b) defines the bottom section level (<h1>..<hb>) only. A string consisting of two digits '
+                'separated by a hyphen in between (`2-5`) defines the top (t) and the bottom (b) (<ht>..<hb>). '
+                'Default: `6` (bottom).'
+            ],
+        }
+        """ Default configuration options. """
+
+        super().__init__(**kwargs)
+
+    def extendMarkdown(self, md):
+        """ Add TOC tree processor to Markdown. """
+        md.registerExtension(self)
+        self.md = md
+        self.reset()
+        tocext = self.TreeProcessorClass(md, self.getConfigs())
+        md.treeprocessors.register(tocext, 'toc', 5)
+
+    def reset(self) -> None:
+        self.md.toc = ''
+        self.md.toc_tokens = []
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return TocExtension(**kwargs)

plugins/code/ui/markdown_preview/markdown/extensions/wikilinks.py

@@ -0,0 +1,96 @@
+# WikiLinks Extension for Python-Markdown
+# ======================================
+
+# Converts [[WikiLinks]] to relative links.
+
+# See https://Python-Markdown.github.io/extensions/wikilinks
+# for documentation.
+
+# Original code Copyright [Waylan Limberg](http://achinghead.com/).
+
+# All changes Copyright The Python Markdown Project
+
+# License: [BSD](https://opensource.org/licenses/bsd-license.php)
+
+"""
+Converts `[[WikiLinks]]` to relative links.
+
+See the [documentation](https://Python-Markdown.github.io/extensions/wikilinks)
+for details.
+"""
+
+from __future__ import annotations
+
+from . import Extension
+from ..inlinepatterns import InlineProcessor
+import xml.etree.ElementTree as etree
+import re
+
+
+def build_url(label, base, end):
+    """ Build a URL from the label, a base, and an end. """
+    clean_label = re.sub(r'([ ]+_)|(_[ ]+)|([ ]+)', '_', label)
+    return '{}{}{}'.format(base, clean_label, end)
+
+
+class WikiLinkExtension(Extension):
+    """ Add inline processor to Markdown. """
+
+    def __init__(self, **kwargs):
+        self.config = {
+            'base_url': ['/', 'String to append to beginning or URL.'],
+            'end_url': ['/', 'String to append to end of URL.'],
+            'html_class': ['wikilink', 'CSS hook. Leave blank for none.'],
+            'build_url': [build_url, 'Callable formats URL from label.'],
+        }
+        """ Default configuration options. """
+        super().__init__(**kwargs)
+
+    def extendMarkdown(self, md):
+        self.md = md
+
+        # append to end of inline patterns
+        WIKILINK_RE = r'\[\[([\w0-9_ -]+)\]\]'
+        wikilinkPattern = WikiLinksInlineProcessor(WIKILINK_RE, self.getConfigs())
+        wikilinkPattern.md = md
+        md.inlinePatterns.register(wikilinkPattern, 'wikilink', 75)
+
+
+class WikiLinksInlineProcessor(InlineProcessor):
+    """ Build link from `wikilink`. """
+
+    def __init__(self, pattern, config):
+        super().__init__(pattern)
+        self.config = config
+
+    def handleMatch(self, m, data):
+        if m.group(1).strip():
+            base_url, end_url, html_class = self._getMeta()
+            label = m.group(1).strip()
+            url = self.config['build_url'](label, base_url, end_url)
+            a = etree.Element('a')
+            a.text = label
+            a.set('href', url)
+            if html_class:
+                a.set('class', html_class)
+        else:
+            a = ''
+        return a, m.start(0), m.end(0)
+
+    def _getMeta(self):
+        """ Return meta data or `config` data. """
+        base_url = self.config['base_url']
+        end_url = self.config['end_url']
+        html_class = self.config['html_class']
+        if hasattr(self.md, 'Meta'):
+            if 'wiki_base_url' in self.md.Meta:
+                base_url = self.md.Meta['wiki_base_url'][0]
+            if 'wiki_end_url' in self.md.Meta:
+                end_url = self.md.Meta['wiki_end_url'][0]
+            if 'wiki_html_class' in self.md.Meta:
+                html_class = self.md.Meta['wiki_html_class'][0]
+        return base_url, end_url, html_class
+
+
+def makeExtension(**kwargs):  # pragma: no cover
+    return WikiLinkExtension(**kwargs)