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