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