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100 lines
3.8 KiB
Python
100 lines
3.8 KiB
Python
import logging
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import os
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import subprocess
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from typing import Any
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import lxml.html
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import requests
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from django.conf import settings
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from zerver.lib.outgoing_http import OutgoingSession
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from zerver.lib.storage import static_path
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class KatexSession(OutgoingSession):
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def __init__(self, **kwargs: Any) -> None:
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# We set a very short timeout because these requests are
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# expected to be quite fast (milliseconds) and blocking on
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# this affects message rendering performance.
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super().__init__(role="katex", timeout=0.5, **kwargs)
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def render_tex(tex: str, is_inline: bool = True) -> str | None:
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r"""Render a TeX string into HTML using KaTeX
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Returns the HTML string, or None if there was some error in the TeX syntax
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Keyword arguments:
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tex -- Text string with the TeX to render
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Don't include delimiters ('$$', '\[ \]', etc.)
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is_inline -- Boolean setting that indicates whether the render should be
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inline (i.e. for embedding it in text) or not. The latter
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will show the content centered, and in the "expanded" form
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(default True)
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"""
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if settings.KATEX_SERVER:
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try:
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resp = KatexSession().post(
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# We explicitly disable the Smokescreen proxy for this
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# call, since it intentionally connects to localhost.
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# This is safe because the host is explicitly fixed, and
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# the port is pulled from our own configuration.
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f"http://localhost:{settings.KATEX_SERVER_PORT}/",
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data={
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"content": tex,
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"is_display": "false" if is_inline else "true",
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"shared_secret": settings.SHARED_SECRET,
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},
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proxies={"http": ""},
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)
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except requests.exceptions.Timeout:
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logging.warning("KaTeX rendering service timed out with %d byte long input", len(tex))
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return None
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except requests.exceptions.RequestException as e:
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logging.warning("KaTeX rendering service failed: %s", type(e).__name__)
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return None
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if resp.status_code == 200:
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return resp.content.decode().strip()
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elif resp.status_code == 400:
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return None
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else:
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logging.warning(
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"KaTeX rendering service failed: (%s) %s", resp.status_code, resp.content.decode()
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)
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return None
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katex_path = (
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static_path("webpack-bundles/katex-cli.js")
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if settings.PRODUCTION
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else os.path.join(settings.DEPLOY_ROOT, "node_modules/katex/cli.js")
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)
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if not os.path.isfile(katex_path):
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logging.error("Cannot find KaTeX for latex rendering!")
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return None
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command = ["node", katex_path]
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if not is_inline:
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command.extend(["--display-mode"])
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try:
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stdout = subprocess.check_output(command, input=tex, stderr=subprocess.DEVNULL, text=True)
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# stdout contains a newline at the end
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return stdout.strip()
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except subprocess.CalledProcessError:
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return None
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def change_katex_to_raw_latex(fragment: lxml.html.HtmlElement) -> None:
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# Selecting the <span> elements with class 'katex'
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katex_spans = fragment.xpath("//span[@class='katex']")
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# Iterate through 'katex_spans' and replace with a new <span> having LaTeX text.
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for katex_span in katex_spans:
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latex_text = katex_span.xpath(".//annotation[@encoding='application/x-tex']")[0].text
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# We store 'tail' to insert them back as the replace operation removes it.
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tail = katex_span.tail
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latex_span = lxml.html.Element("span")
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latex_span.text = f"$${latex_text}$$"
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katex_span.getparent().replace(katex_span, latex_span)
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latex_span.tail = tail
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