44e5de02f8
Also remove HTML_PROCESSOR `filter_inline` and `from_markdown_inline` methods. `filter` and `from_markdown` now take an `inline` argument.
337 lines
11 KiB
Python
337 lines
11 KiB
Python
# SPDX-License-Identifier: LGPL-3.0-or-later
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"""HTML and Markdown processing tools."""
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import re
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import html_sanitizer.sanitizer as sanitizer
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import mistune
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from html_sanitizer.sanitizer import Sanitizer
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from lxml.html import HtmlElement # nosec
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from .svg_colors import SVG_COLORS
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class MarkdownInlineGrammar(mistune.InlineGrammar):
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"""Markdown inline elements syntax modifications for the Mistune parser.
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Modifications:
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- Disable underscores for bold/italics (e.g. `__bold__`)
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- Add syntax for coloring text: `<color>(text)`,
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e.g. `<red>(Lorem ipsum)` or `<#000040>(sit dolor amet...)`
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"""
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escape = re.compile(r"^\\([\\`*{}\[\]()#+\-.!_<>~|])") # Add <
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emphasis = re.compile(r"^\*((?:\*\*|[^\*])+?)\*(?!\*)")
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double_emphasis = re.compile(r"^\*{2}([\s\S]+?)\*{2}(?!\*)")
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# test string: r"<b>(x) <r>(x) \<a>b>(x) <a\>b>(x) <b>(\(z) <c>(foo\)xyz)"
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color = re.compile(
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r"^<(.+?)>" # capture the color in `<color>`
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r"\((.+?)" # capture text in `(text`
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r"(?<!\\)(?:\\\\)*" # ignore the next `)` if it's \escaped
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r"\)", # finish on a `)`
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)
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class MarkdownInlineLexer(mistune.InlineLexer):
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"""Apply the changes from `MarkdownInlineGrammar` for Mistune."""
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grammar_class = MarkdownInlineGrammar
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default_rules = [
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"escape", "color", "autolink", "url", # Add color
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"footnote", "link", "reflink", "nolink",
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"double_emphasis", "emphasis", "code",
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"linebreak", "strikethrough", "text",
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]
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inline_html_rules = [
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"escape", "color", "autolink", "url", "link", "reflink", # Add color
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"nolink", "double_emphasis", "emphasis", "code",
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"linebreak", "strikethrough", "text",
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]
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def output_double_emphasis(self, m):
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return self.renderer.double_emphasis(self.output(m.group(1)))
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def output_emphasis(self, m):
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return self.renderer.emphasis(self.output(m.group(1)))
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def output_color(self, m):
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color = m.group(1)
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text = self.output(m.group(2))
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return self.renderer.color(color, text)
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class MarkdownRenderer(mistune.Renderer):
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def color(self, color: str, text: str):
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"""Render given text with a color using `<span data-mx-color=#hex>`."""
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# This may be a color name, try to get a #hex code for it.
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color = SVG_COLORS.get(re.sub(r"\s", "", color.lower()), color)
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return f'<span data-mx-color="{color}">{text}</span>'
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class HTMLProcessor:
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"""Provide HTML filtering and conversion from Markdown.
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Filtering sanitizes HTML and ensures it complies with the supported Qt
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subset for usage in QML: https://doc.qt.io/qt-5/richtext-html-subset.html
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Some methods take an `outgoing` argument, specifying if the HTML is
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intended to be sent to matrix servers or used locally in our application.
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For local usage, extra transformations are applied:
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- Wrap text lines starting with a `>` in `<span>` with a `quote` class.
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This allows them to be styled appropriately from QML.
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Some methods take an `inline` argument, which return text appropriate
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for UI elements restricted to display a single line, e.g. the room
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last message subtitles in QML or notifications.
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In inline filtered HTML, block tags are stripped or substituted and
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newlines are turned into ⏎ symbols (U+23CE).
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"""
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inline_tags = {
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"span", "font", "a", "sup", "sub", "b", "i", "s", "u", "code",
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}
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block_tags = {
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"h1", "h2", "h3", "h4", "h5", "h6","blockquote",
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"p", "ul", "ol", "li", "hr", "br",
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"table", "thead", "tbody", "tr", "th", "td", "pre",
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}
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link_regexes = [re.compile(r, re.IGNORECASE) for r in [
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(r"(?P<body>[a-zA-Z\d]+://(?P<host>[a-z\d._-]+(?:\:\d+)?)"
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r"(?:/[/\-_.,a-z\d#%&?;=~]*)?(?:\([/\-_.,a-z\d#%&?;=~]*\))?)"),
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r"mailto:(?P<body>[a-z0-9._-]+@(?P<host>[a-z0-9_.-]+[a-z](?:\:\d+)?))",
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r"tel:(?P<body>[0-9+-]+)(?P<host>)",
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r"(?P<body>magnet:\?xt=urn:[a-z0-9]+:.+)(?P<host>)",
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]]
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inline_quote_regex = re.compile(r"(^|⏎)(\s*>[^⏎\n]*)", re.MULTILINE)
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quote_regex = re.compile(
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r"(^|<p/?>|<br/?>|<h\d/?>)(\s*>.*?)(</?p>|<br/?>|</?h\d>|$)",
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re.MULTILINE,
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)
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extra_newlines_regex = re.compile(r"\n(\n*)")
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def __init__(self) -> None:
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self._sanitizers = {
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(False, False): Sanitizer(self.sanitize_settings(False, False)),
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(True, False): Sanitizer(self.sanitize_settings(True, False)),
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(False, True): Sanitizer(self.sanitize_settings(False, True)),
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(True, True): Sanitizer(self.sanitize_settings(True, True)),
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}
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self._inline_sanitizer = Sanitizer(self.sanitize_settings(inline=True))
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self._inline_outgoing_sanitizer = \
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Sanitizer(self.sanitize_settings(inline=True))
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# The whitespace remover doesn't take <pre> into account
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sanitizer.normalize_overall_whitespace = lambda html, *args, **kw: html
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sanitizer.normalize_whitespace_in_text_or_tail = \
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lambda el, *args, **kw: el
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# hard_wrap: convert all \n to <br> without required two spaces
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# escape: escape HTML characters in the input string, e.g. tags
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self._markdown_to_html = mistune.Markdown(
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hard_wrap=True,
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escape=True,
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inline=MarkdownInlineLexer,
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renderer=MarkdownRenderer(),
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)
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self._markdown_to_html.block.default_rules = [
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rule for rule in self._markdown_to_html.block.default_rules
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if rule != "block_quote"
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]
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def from_markdown(
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self, text: str, inline: bool = False, outgoing: bool = False,
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) -> str:
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"""Return filtered HTML from Markdown text."""
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return self.filter(self._markdown_to_html(text), inline, outgoing)
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def filter(
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self, html: str, inline: bool = False, outgoing: bool = False,
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) -> str:
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"""Filter and return HTML."""
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html = self._sanitizers[inline, outgoing].sanitize(html).rstrip("\n")
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if outgoing:
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return html
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# Client-side modifications
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if inline:
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return self.inline_quote_regex.sub(
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r'\1<span class="quote">\2</span>', html,
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)
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return self.quote_regex.sub(r'\1<span class="quote">\2</span>\3', html)
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def sanitize_settings(
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self, inline: bool = False, outgoing: bool = False,
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) -> dict:
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"""Return an html_sanitizer configuration."""
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# https://matrix.org/docs/spec/client_server/latest#m-room-message-msgtypes
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# TODO: mx-reply and the new hidden thing
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inline_tags = self.inline_tags
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all_tags = inline_tags | self.block_tags
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inlines_attributes = {
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"font": {"color"},
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"a": {"href"},
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"code": {"class"},
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}
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attributes = {**inlines_attributes, **{
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"ol": {"start"},
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"hr": {"width"},
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"span": {"data-mx-color"},
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}}
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return {
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"tags": inline_tags if inline else all_tags,
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"attributes": inlines_attributes if inline else attributes,
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"empty": {} if inline else {"hr", "br"},
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"separate": {"a"} if inline else {
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"a", "p", "li", "table", "tr", "th", "td", "br", "hr",
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},
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"whitespace": {},
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"keep_typographic_whitespace": True,
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"add_nofollow": False,
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"autolink": {
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"link_regexes": self.link_regexes,
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"avoid_hosts": [],
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},
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"sanitize_href": lambda href: href,
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"element_preprocessors": [
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sanitizer.bold_span_to_strong,
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sanitizer.italic_span_to_em,
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sanitizer.tag_replacer("strong", "b"),
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sanitizer.tag_replacer("em", "i"),
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sanitizer.tag_replacer("strike", "s"),
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sanitizer.tag_replacer("del", "s"),
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sanitizer.tag_replacer("form", "p"),
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sanitizer.tag_replacer("div", "p"),
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sanitizer.tag_replacer("caption", "p"),
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sanitizer.target_blank_noopener,
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self._span_color_to_font if not outgoing else lambda el: el,
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self._img_to_a,
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self._remove_extra_newlines,
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self._newlines_to_return_symbol if inline else lambda el: el,
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],
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"element_postprocessors": [
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self._font_color_to_span if outgoing else lambda el: el,
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],
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"is_mergeable": lambda e1, e2: e1.attrib == e2.attrib,
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}
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@staticmethod
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def _span_color_to_font(el: HtmlElement) -> HtmlElement:
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"""Convert HTML `<span data-mx-color=...` to `<font color=...>`."""
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if el.tag not in ("span", "font"):
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return el
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color = el.attrib.pop("data-mx-color", None)
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if color:
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el.tag = "font"
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el.attrib["color"] = color
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return el
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@staticmethod
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def _font_color_to_span(el: HtmlElement) -> HtmlElement:
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"""Convert HTML `<font color=...>` to `<span data-mx-color=...`."""
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if el.tag not in ("span", "font"):
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return el
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color = el.attrib.pop("color", None)
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if color:
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el.tag = "span"
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el.attrib["data-mx-color"] = color
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return el
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@staticmethod
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def _img_to_a(el: HtmlElement) -> HtmlElement:
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"""Linkify images by wrapping `<img>` tags in `<a>`."""
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if el.tag == "img":
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el.tag = "a"
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el.attrib["href"] = el.attrib.pop("src", "")
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el.text = el.attrib.pop("alt", None) or el.attrib["href"]
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return el
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def _remove_extra_newlines(self, el: HtmlElement) -> HtmlElement:
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"""Remove excess `\\n` characters from non-`<pre>` HTML elements.
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This is done to avoid additional blank lines when the CSS directive
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`white-space: pre` is used.
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"""
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pre_parent = any(parent.tag == "pre" for parent in el.iterancestors())
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if el.tag != "pre" and not pre_parent:
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if el.text:
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el.text = self.extra_newlines_regex.sub(r"\1", el.text)
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if el.tail:
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el.tail = self.extra_newlines_regex.sub(r"\1", el.tail)
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return el
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def _newlines_to_return_symbol(self, el: HtmlElement) -> HtmlElement:
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"""Turn newlines into unicode return symbols (⏎, U+23CE).
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The symbol is added to blocks with siblings (e.g. a `<p>` followed by
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another `<p>`) and `<br>` tags.
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The `<br>` themselves will be removed by the inline sanitizer.
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"""
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is_block_with_siblings = (el.tag in self.block_tags and
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next(el.itersiblings(), None) is not None)
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if el.tag == "br" or is_block_with_siblings:
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el.tail = f" ⏎ {el.tail or ''}"
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# Replace left \n in text/tail of <pre> content by the return symbol.
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if el.text:
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el.text = re.sub(r"\n", r" ⏎ ", el.text)
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if el.tail:
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el.tail = re.sub(r"\n", r" ⏎ ", el.tail)
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return el
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HTML_PROCESSOR = HTMLProcessor()
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