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# 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_and_remainder, AttrListExtension
from ..util import parseBoolValue
from ..serializers import _escape_attrib_html
import re
from typing import TYPE_CHECKING, Any, Iterable
if TYPE_CHECKING: # pragma: no cover
from markdown import Markdown
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: Markdown, config: dict[str, Any]):
super().__init__(md)
self.config = config
self.checked_for_deps = False
self.codehilite_conf: dict[str, Any] = {}
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: list[str]) -> list[str]:
""" 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)
index = 0
while 1:
m = self.FENCED_BLOCK_RE.search(text, index)
if m:
lang, id, classes, config = None, '', [], {}
if m.group('attrs'):
attrs, remainder = get_attrs_and_remainder(m.group('attrs'))
if remainder: # Does not have correctly matching curly braces, so the syntax is invalid.
index = m.end('attrs') # Explicitly skip over this, to prevent an infinite loop.
continue
id, classes, config = self.handle_attrs(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():]}'
# Continue from after the replaced text in the next iteration.
index = m.start() + 1 + len(placeholder)
else:
break
return text.split("\n")
def handle_attrs(self, attrs: Iterable[tuple[str, str]]) -> tuple[str, list[str], dict[str, Any]]:
""" 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: str) -> str:
""" basic html escaping """
txt = txt.replace('&', '&')
txt = txt.replace('<', '<')
txt = txt.replace('>', '>')
txt = txt.replace('"', '"')
return txt
def makeExtension(**kwargs): # pragma: no cover
return FencedCodeExtension(**kwargs)
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