105 lines
3.4 KiB
Python
105 lines
3.4 KiB
Python
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from __future__ import annotations
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import copy
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from typing import TYPE_CHECKING, Callable
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import markdown
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import markdown.treeprocessors
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if TYPE_CHECKING:
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from xml.etree import ElementTree as etree
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# TODO: This will become unnecessary after min-versions have Markdown >=3.4
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_unescape: Callable[[str], str]
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try:
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_unescape = markdown.treeprocessors.UnescapeTreeprocessor().unescape
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except AttributeError:
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_unescape = lambda s: s
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# TODO: Most of this file will become unnecessary after https://github.com/Python-Markdown/markdown/pull/1441
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def get_heading_text(el: etree.Element, md: markdown.Markdown) -> str:
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el = copy.deepcopy(el)
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_remove_anchorlink(el)
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_remove_fnrefs(el)
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_extract_alt_texts(el)
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return _strip_tags(_render_inner_html(el, md))
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def _strip_tags(text: str) -> str:
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"""Strip HTML tags and return plain text. Note: HTML entities are unaffected."""
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# A comment could contain a tag, so strip comments first
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while (start := text.find('<!--')) != -1 and (end := text.find('-->', start)) != -1:
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text = text[:start] + text[end + 3 :]
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while (start := text.find('<')) != -1 and (end := text.find('>', start)) != -1:
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text = text[:start] + text[end + 1 :]
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# Collapse whitespace
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text = ' '.join(text.split())
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return text
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def _render_inner_html(el: etree.Element, md: markdown.Markdown) -> str:
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# The `UnescapeTreeprocessor` runs after `toc` extension so run here.
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text = md.serializer(el)
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text = _unescape(text)
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# Strip parent tag
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start = text.index('>') + 1
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end = text.rindex('<')
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text = text[start:end].strip()
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for pp in md.postprocessors:
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text = pp.run(text)
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return text
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def _remove_anchorlink(el: etree.Element) -> None:
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"""Drop anchorlink from the element, if present."""
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if len(el) > 0 and el[-1].tag == 'a' and el[-1].get('class') == 'headerlink':
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del el[-1]
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def _remove_fnrefs(root: etree.Element) -> None:
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"""Remove footnote references from the element, if any are present."""
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for parent in root.findall('.//sup[@id]/..'):
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_replace_elements_with_text(parent, _predicate_for_fnrefs)
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def _predicate_for_fnrefs(el: etree.Element) -> str | None:
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if el.tag == 'sup' and el.get('id', '').startswith('fnref'):
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return ''
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return None
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def _extract_alt_texts(root: etree.Element) -> None:
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"""For images that have an `alt` attribute, replace them with this content."""
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for parent in root.findall('.//img[@alt]/..'):
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_replace_elements_with_text(parent, _predicate_for_alt_texts)
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def _predicate_for_alt_texts(el: etree.Element) -> str | None:
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if el.tag == 'img' and (alt := el.get('alt')):
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return alt
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return None
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def _replace_elements_with_text(
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parent: etree.Element, predicate: Callable[[etree.Element], str | None]
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) -> None:
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"""For each child element, if matched, replace it with the text returned from the predicate."""
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carry_text = ""
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for child in reversed(parent): # Reversed for the ability to mutate during iteration.
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# Remove matching elements but carry any `tail` text to preceding elements.
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new_text = predicate(child)
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if new_text is not None:
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carry_text = new_text + (child.tail or "") + carry_text
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parent.remove(child)
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elif carry_text:
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child.tail = (child.tail or "") + carry_text
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carry_text = ""
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if carry_text:
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parent.text = (parent.text or "") + carry_text
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