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HTMLParser stops parsing upon encountering <style> tag #118350

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savchenko opened this issue Apr 27, 2024 · 3 comments
Open

HTMLParser stops parsing upon encountering <style> tag #118350

savchenko opened this issue Apr 27, 2024 · 3 comments
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type-bug An unexpected behavior, bug, or error

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@savchenko
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savchenko commented Apr 27, 2024 •
edited by github-actions bot

Bug report

Bug description:

An example where parsing stops after the <style color="red">:

from html.parser import HTMLParser
from io import StringIO

class HTML2text(HTMLParser):
    def __init__(self):
        super().__init__()
        self.data = StringIO()
    def handle_data(self, html):
        self.data.write(html)
    def get_data(self):
        return self.data.getvalue().strip()

html_test = '''
<!DOCTYPE html>
<head><title>Glued</title></head><body><some><style color="red">title</bar>
<h1>Spacious             </h1><a href="https://heading.net">heading.net</a>
<span>not<a href="https://www.arpa.home">my.home.arpa</a><p>        URL</p>
</body></html>
'''

parser = HTML2text()
parser.feed(html_test)
print(parser.get_data())

Changing a single character in the word "style" restores the normal functionality.

CPython versions tested on:

3.11

Operating systems tested on:

Linux
@savchenko savchenko added the type-bug An unexpected behavior, bug, or error label Apr 27, 2024
@JelleZijlstra
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Isn't this because you didn't close your <style> tag? If I remember correctly style tags go on until </style> is seen regardless of any other tag-like text within the tag, because they may contain text in other languages.

@savchenko
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@JelleZijlstra , indeed! Closing <style> allows the snippet to be parsed. However, isn't it inconsistent with the the behaviour observed when parsing other tags?

For example, this broken HTML is parsed correctly:

<head><title>Rebelious<h1>Heading<a href="https://example.net">example.net
<span>not<a href="https://www.arpa.home">arpa.home<p>Paragraph<h2>and more

@vadmium
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vadmium commented Apr 28, 2024

The difference is that <style> is a “raw text element”. It cannot contain HTML markup. Most other tags can be followed by other markup. See https://html.spec.whatwg.org/multipage/syntax.html#raw-text-elements

However I believe your HTML with <title>Rebelious<h1> . . . does trigger a bug. The <title> element is supposed to be an “escapable raw text element”, so <h1> should be counted as part of the raw title text. However it gets parsed as a tag:

Encountered a start tag: title
Encountered some data : Rebelious
Encountered a start tag: h1

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@savchenko @JelleZijlstra @vadmium