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418 lines
15 KiB
418 lines
15 KiB
"""
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Footnotes Extension for Python-Markdown
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=======================================
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Adds footnote handling to Python-Markdown.
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See <https://Python-Markdown.github.io/extensions/footnotes>
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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 ..preprocessors import Preprocessor
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from ..inlinepatterns import InlineProcessor
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from ..treeprocessors import Treeprocessor
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from ..postprocessors import Postprocessor
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from .. import util
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from collections import OrderedDict
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import re
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import copy
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import xml.etree.ElementTree as etree
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FN_BACKLINK_TEXT = util.STX + "zz1337820767766393qq" + util.ETX
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NBSP_PLACEHOLDER = util.STX + "qq3936677670287331zz" + util.ETX
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DEF_RE = re.compile(r'[ ]{0,3}\[\^([^\]]*)\]:\s*(.*)')
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TABBED_RE = re.compile(r'((\t)|( ))(.*)')
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RE_REF_ID = re.compile(r'(fnref)(\d+)')
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class FootnoteExtension(Extension):
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""" Footnote Extension. """
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def __init__(self, **kwargs):
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""" Setup configs. """
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self.config = {
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'PLACE_MARKER':
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["///Footnotes Go Here///",
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"The text string that marks where the footnotes go"],
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'UNIQUE_IDS':
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[False,
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"Avoid name collisions across "
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"multiple calls to reset()."],
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"BACKLINK_TEXT":
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["↩",
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"The text string that links from the footnote "
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"to the reader's place."],
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"BACKLINK_TITLE":
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["Jump back to footnote %d in the text",
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"The text string used for the title HTML attribute "
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"of the backlink. %d will be replaced by the "
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"footnote number."],
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"SEPARATOR":
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[":",
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"Footnote separator."]
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}
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super().__init__(**kwargs)
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# In multiple invocations, emit links that don't get tangled.
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self.unique_prefix = 0
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self.found_refs = {}
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self.used_refs = set()
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self.reset()
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def extendMarkdown(self, md):
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""" Add pieces to Markdown. """
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md.registerExtension(self)
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self.parser = md.parser
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self.md = md
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# Insert a preprocessor before ReferencePreprocessor
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md.preprocessors.register(FootnotePreprocessor(self), 'footnote', 15)
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# Insert an inline pattern before ImageReferencePattern
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FOOTNOTE_RE = r'\[\^([^\]]*)\]' # blah blah [^1] blah
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md.inlinePatterns.register(FootnoteInlineProcessor(FOOTNOTE_RE, self), 'footnote', 175)
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# Insert a tree-processor that would actually add the footnote div
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# This must be before all other treeprocessors (i.e., inline and
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# codehilite) so they can run on the the contents of the div.
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md.treeprocessors.register(FootnoteTreeprocessor(self), 'footnote', 50)
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# Insert a tree-processor that will run after inline is done.
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# In this tree-processor we want to check our duplicate footnote tracker
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# And add additional backrefs to the footnote pointing back to the
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# duplicated references.
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md.treeprocessors.register(FootnotePostTreeprocessor(self), 'footnote-duplicate', 15)
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# Insert a postprocessor after amp_substitute processor
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md.postprocessors.register(FootnotePostprocessor(self), 'footnote', 25)
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def reset(self):
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""" Clear footnotes on reset, and prepare for distinct document. """
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self.footnotes = OrderedDict()
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self.unique_prefix += 1
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self.found_refs = {}
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self.used_refs = set()
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def unique_ref(self, reference, found=False):
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""" Get a unique reference if there are duplicates. """
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if not found:
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return reference
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original_ref = reference
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while reference in self.used_refs:
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ref, rest = reference.split(self.get_separator(), 1)
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m = RE_REF_ID.match(ref)
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if m:
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reference = '%s%d%s%s' % (m.group(1), int(m.group(2))+1, self.get_separator(), rest)
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else:
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reference = '%s%d%s%s' % (ref, 2, self.get_separator(), rest)
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self.used_refs.add(reference)
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if original_ref in self.found_refs:
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self.found_refs[original_ref] += 1
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else:
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self.found_refs[original_ref] = 1
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return reference
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def findFootnotesPlaceholder(self, root):
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""" Return ElementTree Element that contains Footnote placeholder. """
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def finder(element):
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for child in element:
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if child.text:
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if child.text.find(self.getConfig("PLACE_MARKER")) > -1:
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return child, element, True
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if child.tail:
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if child.tail.find(self.getConfig("PLACE_MARKER")) > -1:
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return child, element, False
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child_res = finder(child)
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if child_res is not None:
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return child_res
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return None
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res = finder(root)
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return res
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def setFootnote(self, id, text):
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""" Store a footnote for later retrieval. """
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self.footnotes[id] = text
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def get_separator(self):
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""" Get the footnote separator. """
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return self.getConfig("SEPARATOR")
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def makeFootnoteId(self, id):
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""" Return footnote link id. """
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if self.getConfig("UNIQUE_IDS"):
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return 'fn%s%d-%s' % (self.get_separator(), self.unique_prefix, id)
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else:
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return 'fn{}{}'.format(self.get_separator(), id)
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def makeFootnoteRefId(self, id, found=False):
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""" Return footnote back-link id. """
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if self.getConfig("UNIQUE_IDS"):
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return self.unique_ref('fnref%s%d-%s' % (self.get_separator(), self.unique_prefix, id), found)
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else:
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return self.unique_ref('fnref{}{}'.format(self.get_separator(), id), found)
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def makeFootnotesDiv(self, root):
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""" Return div of footnotes as et Element. """
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if not list(self.footnotes.keys()):
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return None
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div = etree.Element("div")
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div.set('class', 'footnote')
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etree.SubElement(div, "hr")
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ol = etree.SubElement(div, "ol")
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surrogate_parent = etree.Element("div")
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for index, id in enumerate(self.footnotes.keys(), start=1):
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li = etree.SubElement(ol, "li")
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li.set("id", self.makeFootnoteId(id))
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# Parse footnote with surrogate parent as li cannot be used.
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# List block handlers have special logic to deal with li.
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# When we are done parsing, we will copy everything over to li.
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self.parser.parseChunk(surrogate_parent, self.footnotes[id])
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for el in list(surrogate_parent):
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li.append(el)
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surrogate_parent.remove(el)
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backlink = etree.Element("a")
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backlink.set("href", "#" + self.makeFootnoteRefId(id))
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backlink.set("class", "footnote-backref")
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backlink.set(
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"title",
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self.getConfig("BACKLINK_TITLE") % (index)
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)
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backlink.text = FN_BACKLINK_TEXT
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if len(li):
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node = li[-1]
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if node.tag == "p":
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node.text = node.text + NBSP_PLACEHOLDER
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node.append(backlink)
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else:
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p = etree.SubElement(li, "p")
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p.append(backlink)
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return div
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class FootnotePreprocessor(Preprocessor):
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""" Find all footnote references and store for later use. """
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def __init__(self, footnotes):
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self.footnotes = footnotes
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def run(self, lines):
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"""
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Loop through lines and find, set, and remove footnote definitions.
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Keywords:
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* lines: A list of lines of text
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Return: A list of lines of text with footnote definitions removed.
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"""
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newlines = []
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i = 0
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while True:
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m = DEF_RE.match(lines[i])
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if m:
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fn, _i = self.detectTabbed(lines[i+1:])
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fn.insert(0, m.group(2))
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i += _i-1 # skip past footnote
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footnote = "\n".join(fn)
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self.footnotes.setFootnote(m.group(1), footnote.rstrip())
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# Preserve a line for each block to prevent raw HTML indexing issue.
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# https://github.com/Python-Markdown/markdown/issues/584
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num_blocks = (len(footnote.split('\n\n')) * 2)
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newlines.extend([''] * (num_blocks))
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else:
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newlines.append(lines[i])
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if len(lines) > i+1:
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i += 1
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else:
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break
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return newlines
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def detectTabbed(self, lines):
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""" Find indented text and remove indent before further proccesing.
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Keyword arguments:
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* lines: an array of strings
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Returns: a list of post processed items and the index of last line.
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"""
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items = []
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blank_line = False # have we encountered a blank line yet?
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i = 0 # to keep track of where we are
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def detab(line):
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match = TABBED_RE.match(line)
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if match:
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return match.group(4)
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for line in lines:
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if line.strip(): # Non-blank line
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detabbed_line = detab(line)
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if detabbed_line:
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items.append(detabbed_line)
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i += 1
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continue
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elif not blank_line and not DEF_RE.match(line):
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# not tabbed but still part of first par.
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items.append(line)
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i += 1
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continue
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else:
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return items, i+1
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else: # Blank line: _maybe_ we are done.
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blank_line = True
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i += 1 # advance
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# Find the next non-blank line
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for j in range(i, len(lines)):
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if lines[j].strip():
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next_line = lines[j]
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break
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else:
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# Include extreaneous padding to prevent raw HTML
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# parsing issue: https://github.com/Python-Markdown/markdown/issues/584
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items.append("")
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i += 1
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else:
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break # There is no more text; we are done.
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# Check if the next non-blank line is tabbed
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if detab(next_line): # Yes, more work to do.
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items.append("")
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continue
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else:
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break # No, we are done.
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else:
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i += 1
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return items, i
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class FootnoteInlineProcessor(InlineProcessor):
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""" InlinePattern for footnote markers in a document's body text. """
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def __init__(self, pattern, footnotes):
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super().__init__(pattern)
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self.footnotes = footnotes
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def handleMatch(self, m, data):
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id = m.group(1)
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if id in self.footnotes.footnotes.keys():
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sup = etree.Element("sup")
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a = etree.SubElement(sup, "a")
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sup.set('id', self.footnotes.makeFootnoteRefId(id, found=True))
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a.set('href', '#' + self.footnotes.makeFootnoteId(id))
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a.set('class', 'footnote-ref')
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a.text = str(list(self.footnotes.footnotes.keys()).index(id) + 1)
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return sup, m.start(0), m.end(0)
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else:
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return None, None, None
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class FootnotePostTreeprocessor(Treeprocessor):
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""" Amend footnote div with duplicates. """
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def __init__(self, footnotes):
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self.footnotes = footnotes
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def add_duplicates(self, li, duplicates):
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""" Adjust current li and add the duplicates: fnref2, fnref3, etc. """
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for link in li.iter('a'):
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# Find the link that needs to be duplicated.
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if link.attrib.get('class', '') == 'footnote-backref':
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ref, rest = link.attrib['href'].split(self.footnotes.get_separator(), 1)
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# Duplicate link the number of times we need to
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# and point the to the appropriate references.
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links = []
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for index in range(2, duplicates + 1):
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sib_link = copy.deepcopy(link)
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sib_link.attrib['href'] = '%s%d%s%s' % (ref, index, self.footnotes.get_separator(), rest)
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links.append(sib_link)
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self.offset += 1
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# Add all the new duplicate links.
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el = list(li)[-1]
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for l in links:
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el.append(l)
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break
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def get_num_duplicates(self, li):
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""" Get the number of duplicate refs of the footnote. """
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fn, rest = li.attrib.get('id', '').split(self.footnotes.get_separator(), 1)
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link_id = '{}ref{}{}'.format(fn, self.footnotes.get_separator(), rest)
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return self.footnotes.found_refs.get(link_id, 0)
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def handle_duplicates(self, parent):
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""" Find duplicate footnotes and format and add the duplicates. """
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for li in list(parent):
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# Check number of duplicates footnotes and insert
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# additional links if needed.
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count = self.get_num_duplicates(li)
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if count > 1:
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self.add_duplicates(li, count)
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def run(self, root):
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""" Crawl the footnote div and add missing duplicate footnotes. """
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self.offset = 0
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for div in root.iter('div'):
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if div.attrib.get('class', '') == 'footnote':
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# Footnotes shoul be under the first orderd list under
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# the footnote div. So once we find it, quit.
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for ol in div.iter('ol'):
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self.handle_duplicates(ol)
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break
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class FootnoteTreeprocessor(Treeprocessor):
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""" Build and append footnote div to end of document. """
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def __init__(self, footnotes):
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self.footnotes = footnotes
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def run(self, root):
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footnotesDiv = self.footnotes.makeFootnotesDiv(root)
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if footnotesDiv is not None:
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result = self.footnotes.findFootnotesPlaceholder(root)
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if result:
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child, parent, isText = result
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ind = list(parent).index(child)
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if isText:
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parent.remove(child)
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parent.insert(ind, footnotesDiv)
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else:
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parent.insert(ind + 1, footnotesDiv)
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child.tail = None
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else:
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root.append(footnotesDiv)
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class FootnotePostprocessor(Postprocessor):
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""" Replace placeholders with html entities. """
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def __init__(self, footnotes):
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self.footnotes = footnotes
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def run(self, text):
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text = text.replace(
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FN_BACKLINK_TEXT, self.footnotes.getConfig("BACKLINK_TEXT")
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)
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return text.replace(NBSP_PLACEHOLDER, " ")
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def makeExtension(**kwargs): # pragma: no cover
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""" Return an instance of the FootnoteExtension """
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return FootnoteExtension(**kwargs)
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